Wednesday, 4 December 2019

Just a bit of fun

I think this hobby should be fun. It should not be all about understanding Faraday Rotation or precision frequency measurement. Sometimes we should just leave the work to one side and do something for ourselves.

The thing I left aside is a posting on this blog about how to tell the difference between the various VHF propagation methods. Stirring stuff. Like many of my postings it is far too long, too wordy, too ... too much like hard work really. They must be a right pain to read.

For a few days the barometric pressure has been rising as an anticyclone passes across Britain roughly from North West to South East.
There was a weather system across Scotland which was likely to spoil things a bit, but for about 5 days the Hepburn Tropo Predictions (see link on sidebar) have been suggesting that yesterday, Tuesday 3 December 2019, would be the day when VHF and UHF conditions might improve.

So I set Tuesday 3 December 2019 aside as a day to work a few stations and see how I got on.

I really enjoyed it. Good fun.

The significance of Tuesday is that it is the "Activity Contest" day in Europe. Well, it was, until we started having 6m and 4m activity days on Thursdays, which is a good idea but does make it all more complex. This was done because, despite the constant nagging from contesters, the national radio societies were unable to fit six Tuesdays into every month. Those national societies - what good are they if they cannot regulate the number of Tuesdays in the month.

First Tuesday in the month is 2m activity contest day. Now, as is well known, I do not enter contests but I do give away points. So the plan for this Tuesday was to operate as much DX as I could if conditions were good during the day, and then help out in the contest for even more DX during contest hours.

The RSGB National Activity contests run from 20:00 to 22:30 UTC for all modes, with earlier contests from 19:00 to 19:55 for FM and data modes. However, as conditions were looking up, I decided to switch to my favourite contest, the Nordic Activity Contest (NAC), which runs from 18:00 to 22:00 UTC on Wintertime Tuesdays (switching by an hour during daylight saving time).

For this contest I decided to stick to FT8. As the many of the NAC stations use FT8 in its European contest mode I can get a useful updated conest log on WSJT-X which saves me trouble checking for those stations I have already worked.
Contest log with WSJT-X in the "EU VHF Contest Special Operating Activity" mode
Interestingly the latest entry in the log is at the top numbered one, whereas the serial numbers (which I have not managed to capture in the above screen grab) go the other way.

The signal reports used in the European contest mode are "59" type RS strength reports with a serial number, rather than the conventional FT8 "dB S/N relative to the noise in the SSB filter" type reports. If presented with a Euro contest type report WSJT-X will switch over to that style until you dive into the settings and turn it off. Using two different styles of report in two contests running at the same time causes endless confusion to those in the RSGB data contests which do not use serial numbers or the Euro contest system. It all adds to the fun. 

I like the NAC because of its informality. It also helps that the stations involved are usually at a handy distance if conditions are good. Often I can use meteor scatter, but perhaps this time tropo would be good as the high pressure seemed to be perfectly placed. Tropo openings are often best just as the high pressure is subsiding, which it obligingly did.

As usual, click on the images if you wish to enlarge them.
Stations worked at GM4FVM on 144MHZ on 3 December 2019

As the NAC on the first Tuesday of the month is for 2m I did concentrate on that band, but I did some 70cms too. You don't need a contest to make UHF DX interesting, but sometimes it helps.
Stations worked at GM4FVM on 432MHz on 3 December 2019
Before the NAC began I worked 18 stations. On 144MHz it was 14 stations in 8 DXCC, on 432MHz it was 4 stations in 2 DXCC. I only worked France on 432MHz (twice), the others on 144MHz being G, GM, GW, GI, OZ, PA, DL and ON. ON4POO kicked the whole thing off, as he so often does. The two stations in France were F5APQ and F4HRD both in JO00, which isn't bad on 70cms at about 600km from here. I bet I could have worked more stations on 70cms if there had been more around, and of course during the 2m contest the 70cms activity fell (but did not stop!).

During the NAC I worked 10 stations in OZ, LA, and SM of course, plus PA0O as yet another participant in NAC. I was only on for about 2 hours of the contest as I had to go and watch "Masterchef The Professionals" on the television. We have to keep it fun you know.

After the contest I worked 4 stations on 2m (SM and OZ) and then one on 70cms (OZ).

Grand total
For 2m, 30 QSOs over 13 hours and 18 minutes, 18 squares, 10 DXCC, ODX SM7EGM in JO65 at 988km, and
For 70cm, 5 QSOs over 12 hours and 4 minutes, 3 squares, 3 DXCC, ODX OZ2ND in JO46 at 690km.

I am not sure if 70cms contacts count double the distance but they should. Two other contacts that got away were both GI6ATZ, heard on 70cm and 23cms. Either would have been an interesting QSO, and on 23cms a new country for me. However, as the contest was underway I left him to it.

So, I did not enter another contest. I just did some operating. Including a contest is easy when you do not have the keep any records for your entry and it does not matter much if you slope off to watch the telly for a couple of hours.

There was nothing special about 3 December 2019. It was just a chance to work a bit of tropo with the activity level which comes with the contest.

Along the way I did nip outside and change over my 432MHz masthead preamp. I have done this several times over the past 6 months and I have honed the time down from an hour to just 27 minutes. It is getting like a Formula 1 pit stop. I need to work out what is happening. Perhaps that will not be so much fun as a day's operating.

73

Jim
GM4FVM
  






Friday, 15 November 2019

FT8 and 100hz ripple, a strange one for me

The general idea behind sound-card based data modes is that you transmit some tones from your computer using a transceiver, and then use the computer to decode the tones created by others which you receive in reply.

This makes things pretty easy technically. You need steady tones, stable radios and well adjusted sound levels. Modern equipment available to radio amateurs make the whole process fairly simple and reliable. Having said that, rather than amateur radio gear, the tones come from your computer sound card, and who knows about the purity or fidelity of that?

Neil, G4DBN, gave a useful talk on FT8 at the 2018 RSGB Convention. This was recorded by the RSGB and you can find it on YouTube here. If you use data modes I really do encourage you to take the time to watch Neil's presentation.

Neil suggests that it is a good idea to monitor your signal to make sure there is nothing odd going on.

Now, as it all (i.e. all those modes including FT8) relies on everybody being in the same receive and transmit filter bandwidths, the potential for an unwanted signal getting through are quite high. If you are transmitting a 500hz tone, you might generate a 1500hz harmonic, and as that is within a typical 2.7kHz or so filter, you will transmit that and it will be heard by everyone.

Luckily, that type of harmonic is not so common and you can solve it by raising your transmit frequency to 1500hz, whereupon that harmonic becomes 4500hz and is way outside the filter. It would still be there but it would never get transmitted and never get heard. If we ever go beyond the standard SSB-type filter to using really wideband signals then we will have to find a better solution than that, but then we will probably have such superb modes then that we won't care.

Returning to the real world, I thought it best to keep monitoring my digital signals and I still check from time to time. I was thinking that I might find a harmonic of the type I describe above, maybe capable of being resolved by altering the drive at some stage or other.

Oh dear. This latest test was not what I expected to see...
GM4FVM monitoring his own FT8 signal producing multiple decodes (click to enlarge).
In this instance you can see two parallel signals on the wide graph, each 100hz away from the main signal. Both of them are decoding and the worst is showing up as -30dB below the main signal. You can just about make out another pair 100hz further out.

The set-up I was using was transmitting into a dummy load on an IC-7100, receiving on an IC-9700. I could juggle it about, tx on the IC-9700, rx on the IC-7100, or between two IC-7100s, on 70cm, or 2m, and then using an IC-7300 and the 7100s, on 70MHz or 50MHz bands the results were broadly the same.

These are not harmonics of the wanted signals. They have nothing to do with over-modulating using the wanted signal. These are extra modulation products introduced either in the computer sound card or the transmitter.

Something was allowing 100hz into my system. The FT8 signal was then effectively being modulated at 100hz in what I imagine to be an AM-style (unwanted) method. The harmonics of the unwanted 100hz signal are producing mirror images 100hz away. All of this is at far higher levels of RF output than I consider to be acceptable. -30dB is FAR too strong for an in-band unwanted signal for me. In this case it is not just in-band, it is in-filter (if such a compound word exists). I was generating something that others could hear, and those others might be listening for weak signals and not liking what I was doing.

I consulted various people about how important this is and the consensus of opinion was that "it depends". "It isn't good but did anyone complain?" "Is it somehow appearing in the receiver and you am not transmitting it at all?" And several who have heard me say that there is nothing untoward visible or audible on my signal. This last comment is very comforting, but of course it only adds to my knowledge of my signal if they are hearing me 30dB above their threshold - if I am weaker than that they would not hear or see the unwanted signals. However, say during a Sporadic E opening when signals are strong, someone else might hear them loud and (not) clear.

Before going too far I checked to see that this was not an artifact turning up in the receiver. Using four radios, both ways, it was still there. And it was not on most signals received from other amateurs. The theory that this was in my transmitted signal was tested later and it certainly does not seem to be the receivers at fault.

Nevertheless, some received signals do have that effect on them and it was pretty easy to see that it was not introduced at my end. I have been on the receiving end of these hums being transmitted by others, but equally strong signals received at the same time are clean. Here is one from a station in Hungary ...
A certain HA station as decoded on 70MHz by GM4FVM in 2019
Note that as this guy faded out as shown by the trace at 13:15:30, the two unwanted signals faded not long before the main one, meaning that they were strong in relation to it. -18dB according to WSJT that day. This evidence made me more certain that I needed to eliminate my unwanted signals. Although some advice was that "if no locals could hear it then it didn't matter", I know that I can see such things on DX stations who are loud. And anyway, I do not want to radiate unwanted signals.

And these things can get worse. The evidence I produced suggested it changed depending on the radio in use and maybe just over time. Here is the worst I saw me manage, with 6 of my traces which were all decoded..
GM4FVM and his unwated FT8 friends captured at their worst by ... GM4FVM
In this case the strengths recorded for the unwanted signals relative to the wanted one by WSJT were -21, -29, -34, -42 and -43. This translates to the strongest unwanted one showing up as a signal of +01dB. As the wanted signal was +19, that means that during a Sporadic E opening similar to the one I saw the HA station, I would decode 3 of his traces and he would decode 6 of mine.

It just isn't good enough. Something must be done.

It does not really matter to me that other stations are doing it too, nor that no locals are complaining (there are no locals to complain anyway). I just had to clean up my signal.

Lacking any calibrated way to measure this, and recognising that some oddities might remain and pass through my filters, the target for fixing it was no decodable traces here apart from the wanted one. That suggests better than -43dB. Further, I wanted to get to no multiple traces visible at all, decodable or not, which looks like -50dB or more.

"ALARP" they called it during my time working with the railway industry. Any unwanted thing not capable of full control should be "as low as reasonably possible". Maybe I could not reach perfection, but I should try.

Turning back to G4DBN's RSGB lecture he quite correctly states that this type of effect is usually caused by 100hz ripple from switch-mode power supplies (SM-PSUs). It is well known that SM-PSUs can produce ripple on the DC output at twice the input AC frequency. Thus in parts of the world with 60hz mains supply this presumably causes traces with 120hz spacings.

My first line of thinking was that the station SM-PSUs must be generating 100hz ripple and that is getting into the radios. I changed all of the main SM-PSUs for analogue ones. There are two PSUs for the main rigs, one for the ancillaries (SWR meter, network radio,  Hy-Gain rotator controller ...) and one for the 70cms linear amplifier. No change. So they are in the clear. Despite this finding, I changed these around several times because I felt sure the fault lay there. No, it didn't.

Second were SM-PSUs which are not directly connected to the radios and are not what you would call "amateur grade" kit. Shop bought things. An early target was the computer, where any ripple reaching the sound card would explain the multiple traces. I changed the computer, but this made no difference. Then there were the computer displays, the supply for a multi-socket USB 3.0 outboard hub and finally one that produces 20 volts for the SPID rotator and 5V for the GPS standard. Nope, nothing.

By the end of this second phase I was beginning to think that the ripple must be generated somewhere else and be getting back down the mains into the equipment. This seemed highly unlikely. The whole idea of an SM-PSU is that it chops up the mains, generates higher frequency AC, and processes that. How 100hz hum would pass through  that I have no idea. For sure, SM-PSUs can generate their own 100hz hum, but can they allow 100hz hum coming down the mains to pass through?

However unlikely something is, if you have eliminated all the likely options, the unlikely ones have to be checked out. Sherlock would have loved me.

By this stage I had checked all the likely and all the unlikely options and nothing was the culprit. I still thought this must be something wrong with the FT8 signal going into the radio.

I should have realised sooner. The audio input graphical display on the IC-9700 and IC-7300 both showed clean audio coming out of the computer into the radios. This ripple had to be getting into the radios by some other means, but the penny had not dropped with me yet. That was a result I dismissed, and thus overlooked a clue.

Phase three had to be more radical. Even while I ignored a clue that proved it, I was beginning to think that this was getting into the radios by some odd means. If it was possible that this effect was not generated or passing through the computer then just monitoring a plain carrier would show no multiple traces. How could it? A plain carrier is unlikely to be modulated by 100hz hum coming from a computer which is turned off and disconnected.

So stage three saw one radio transmit a single carrier (CW key down or RTTY with no modulation), into a dummy load which was monitored by an SDR receiver with the trace observed on the waterfall. Both radios were powered from separate linear PSUs and entirely separate on both the DC and RF sides. Everything else was turned off and unplugged at the mains. Sure enough no multiple images. But then as I gradually connected various parts of the shack and powered them at the mains (there are three separate mains circuits), look what I saw ...
Tah-dah! The effect as seen on an otherwise unmodulated carrier.
When I connected the third mains circuit multiple traces appeared. In fact, I could toggle them on and off.

It took a while for this to make sense. Somehow a radio sending plain carrier and a receiver receiving it were producing or detecting 100hz modulation from some device not connected to them. The only obvious point of contact was the mains and that did not seem like a likely route (though possible). This had nothing to do with sound cards or FT8, though that was how I first noticed it. My computer was disconnected the whole time during phase three testing.

On then to determine which item on that circuit could be doing this. Obviously it must be ... nope, nothing obvious was doing it. The only thing left is the shack light, a fluorescent anglepoise which appears in my QRZ shack photo. As early mains powered LED lights were (radio) noisy I used a U-shaped fluorescent when the shack was built, and later replaced it was an identical one when the base broke. Could this be the cause? Surely not ...
Effect of light on and off as seen on the IC-9700 waterfall (click to enlarge if necessary).
Yes, the shack light was doing the damage. I will spare you the rest of the investigation. I tested with a reasonably close station on FT8 showed that with the light turned off they were seeing no sign of multiple traces. No amount of testing on my part showed any effect on received signals, so I am pretty sure (but not absolutely certain) that these multiple traces were generated on transmit  only. On testing on FT8, with any combination of radio (IC-7300, IC-9700 and two IC-7100s), turning the light on and off produced and removed the multiple traces. With the light off there were NO extra traces here, decoded or otherwise, visible or even partly visible, other than the main one.

The culprit
Gradually turning on the other SM-PSUs there were some slight bumps at 100hz intervals visible on the SDR waterfalls. They seemed to be -50dB or lower as I reached full operation. None of these were visible on the FT8 waterfall. I suppose these are the residual products of the switch mode process and I shall probably have to accept that. Some things, like computers and their display screens, would be hard to convert to analogue PSUs. I have to accept these unwanted outputs as ALARP, as low as I can make them. They have not gone away though, and will still be heard if my signal is very strong. I will return to the task of making them weaker later.

So the obvious thing to do is to turn off the shack anglepoise lamp. OK. I bought a cheap (£6) LED light with a flexible mount. This runs on 5 volts which is supplied by my (now tested) auxiliary PSU for the SPID rotator and the GPS receiver. So that is it sorted.

Or is it?

I am a radio amateur. I cannot just turn off the light without some investigation of how four separate radios managed to produce unwanted products without some explanation. How did it happen?

Also, as a radio amateur I am used to chasing round RF interference, clamping ferrites all over the place. And ferrites really do work very well against RF interference. But I am no expert on 100hz. I have read up that "electronic ballasts" on fluorescent lights, which have largely replaced the "electric" ballasts and starters, can indeed generate 100hz ripple. But how does this get into my radios?
The ballast for the lamp was held in a plastic box which broke up when opened to reveal this




Searching the Internet for the ballast using the reference number finds the manufacturer and the product name but anything else comes up as "404 error, page not found". I suspect that the BS EN standard referred to relates to double insulated (non-grounded) power supplies. Anyway I cannot get into the ballast itself and I only have generic circuit diagrams to work out what it is. Whilst it certainly might produce 100hz ripple, the means of transmission remains unclear to me.


The only suggestion I can put forward is that somehow this hum is being transmitted inductively. My set-up has lots of potential for hum loops. The radios are all grounded in multiple ways which are hard to disentangle - via the linears, at the power supplies, via the computer, via the SWR meter. And then the computer and the SWR meter are grounded together via the computer cables anyway ... and so it goes on. There is a rat's nest of DC wiring to provide lots of scope to pick up some low frequency energy and share it around via various routes with different impedances. Then again it might simply be passing through the mains (though I cannot really see how).

Even if that is the case, how can it be getting into the rigs? All four rigs in fact? I cannot test removing the DC supply cable, but I did remove the USB lead and the GPS frequency standard for the IC-9700. It cannot be getting down the coax, surely.

I am left with the impression that the lamp is leaking 100hz ripple down its mains lead (not grounded of course), and then inducing a similar ripple in the radio DC leads, or in the other DC connections and thus linking indirectly to the radio DC leads. In then gets inside the radios where it must be doing some mischief. How that modulation occurs I have no idea.

The inevitable consequence of all this is that there must a be a lot of energy coming out of the lamp down the mains cable, which also seems intuitively wrong. But then, touching the lamp holders of my bedside lamp in the days of coiled fluorsecents allowed me to feel the 100hz ripple via my skin. Those lamp ballasts must be a big inductive load.

Anyway, it has gone now. Banished from the house into the garage where it can do no harm. I did try it on a different circuit in the house but the effect was the same. As I cannot be in the garage and the shack the same time I doubt if it will cause any harm out there.

As for the future, there are lots of "mains conditioner" type multi-socket boards designed to cope with this type of thing. They are mostly aimed at musicians using amplifiers during stage shows. The drawback is that they generally have no technical specifications worth the title. They claim to stop mains hum, but do they? Even then, they will not stop anything generated in the PSU and passed on down the DC line into the radio, though they would stop anything radiating through the mains (if they work at all, that is).

I am left feeling uncomfortable. After 10 days of heaving about power supplies and digging under the bench I have an answer to "what" but no answer to "why". The lamp and the immediate effects are gone, but my equipment has been shown to be susceptible to a form of interference against which I have no real defence.

The inquiring mind is never satisfied.

73

Jim

GM4FVM



Thursday, 7 November 2019

Round the microwave table and more doubts about radio.

I feel like a kid explaining why he has been late for school.

I missed the National Ham Rally as I was away. I was also away for the Fog of the Tyne Rally. I missed the Galashiels Rally because my car was off the road for a week to be fitted with a £900 towbar. A £900 towbar? That is new rig money for something used to haul grass cuttings to the local dump.

I had no excuse when it came to the Scottish Microwave Round Table last weekend (apart from being broke after spending £900 on a towbar).






Heather, G0HMO, giving her talk on SDRs for portable microwave operation
I took the train to Burntisland, and the Museum of Communication is a short walk from the station there. There were 55 people there and it was great to meet Roger GM4PMK, Peter GM8GAX, Andy GM7GDE, Gordon GI6ATZ, Gordon G8PNN, Brian G8KPD, Eddie G0EHV, Norman G3ZWR, Jon GM4JTJ, Geoffrey GI0GDP, Barry GM4TOE, and Tom GM8MJV. Sorry if I missed anyone out of that list and I spoke to several more who I cannot recall right now. There was a lot going on.

In fact, despite the list people I did talk to, there were several more I hoped to meet but who escaped me as I circulated around.

It was a pleasure to receive my latest batch of QSL cards. Andy, GM7GDE, who is the RSGB QSL Bureau sub-manager for my callsign, had gone to the trouble of checking who would be at the meeting and bringing along their cards to save postage and time.

Being the sub-manager cannot be an easy job, and adding this personal element to his already excellent service was really appreciated. Thanks Andy.

The first talk was about Microwave EME. I have dabbled with moonbounce on VHF and UHF, but never on microwaves, so that was interesting.

Then we heard from Sam, G4DDK, about the technical aspects of the Icom IC-9700. Sam has written the review for practical wireless. I provided a link to Sam's article in my non-technical review on this blog here. Various things had changed since the review was written.

It was interesting to hear that some 9700 owners have still felt it is worth fitting an internal modification to the 9700 to give even more frequency accuracy than the 10MHz reference method. This involves swamping the 9700 master oscillator with a board soldered over the oscillator's shielding box. So although it does involve delving into the radio, no actual soldering of wires is needed as far as I can see. The replacement board couples inductively to the existing circuit and overrides the on-board master oscillator with a GPS or similar one mounted (presumably) outside the case. So far I find the 10MHz reference input to be fine for my purposes. So far anyway.

When prompted with a question about the single PTT output, Sam said that someone makes a CI-V operated outboard switching device, but he did not say who. I cannot find any reference to this item being on sale. Someone in the audience suggested using the DC pre-amp bias as a switch but I doubt if this will work as they are all on so that you can receive on two bands at once. I should check if they all go off on transmit or just the one in use for transmit at the time. If that did work, I would need to sequence all my preamps together on the PTT line.Also, can my sequencer supply enough current for all three pre-amps? Probably, yes, but I need to check. I would also need 6 bias-tees, two for each band, or do some surgery inside the case to reduce that to three.

The lunch interval provided a good opportunity for networking.

After that GM8IEM talked about constructing a 13cm home station around the Kuhne transverter. This was interesting, though 13cms is a bit far for me to think about when I am only just starting on 23cms.

Finally Heather, M0HMO, rounded things off by talking about SDRs and software for portable microwave operation. The idea was that a movement could emerge to provide a route into microwaves for new operators by utilising the latest SDR technology. This became a bit complex and I got left behind at times as I tried to interpret the jargon and initials in use. However, I got the gist of it and it seems like a good idea. I doubt if I will be mountain-topping soon though.

Neil, G4BDN, was presented with the constructors prize. The quality of his work is astoundingly good.

I also bought something at one of the sales stalls - an RF transfer relay. This is a possible solution to switching a linear amplifier I plan to use on 23cms. I say plan, but I have not decided which way to go on this project. Bert Modderman, PE1RKI, (site here), makes an interesting range of amplifiers, some of which might suit my needs.

Bert specifically states that you should not use transfer relays with his amplifiers. This is because they usually connect the input to the output of the linear on receive, opening the door to all sorts of problems.

Despite Bert's comments I still bought this one.
The diagram shows J1 and J2, plus J3 and J4, normally open as you would expect, but only J2 to J4 normally closed. So J1 and J3 are always open and I can connect my linear there and activating the relay will bring it into circuit. Otherwise that diagram suggests that the linear will be isolated and received signals can pass between J2 and J4 when not energised.

Well, so it says on the box, and checking it out with a multimeter suggests it should work. This was on sale at a good price for a transfer relay, but still rather expensive for me. I didn't have the money on me and I had to post a cheque afterwards to GM8GAX. Thanks Peter. I didn't have the cash due to spending £900 on a towbar, not that I am obsessed or neurotic about that. Oh no, I have forgotten all about that. Forgive and forget, I say.

This particular transfer relay came from a clearance sale of more items from David, the late GM4JJJ, so I guess he had the same idea as I did. I hope so anyway.

VK4GHZ's posting sets this out better than I could: here  http://vk4ghz.com/transfer-relays/

After reading VK4GHZ's posting I had been looking for one of these rather rare variants for some time. As I pondered it at the sale table, some helpful Microwaver pointed out that the next stand had a transfer relay for half the price. When I explained the unusual configuration of this one he looked blankly at me. The other one might be half the price, but it is not suitable for my plan.

But I don't have a proper plan for more power on 23cms. I have the rig, coax, preamp, sequencer, bias tee, antenna  and now the relay, but not the power amplifier. I am not convinced that the Bert Modderman route is the right way for me to go.

Here is the history for me. On every band I now use I have gone in barefoot or with low-ish power. Then after a while I have bought a bigger amplifier and in every case it would have been cheaper and easier to get the larger amplifier at the start.

However, I live in this twilight world of love/hate for radio. Every so often I want to go QRT and take up quilting. Or follow in my Granny's footsteps and try crochet. Making blankets is an Edgar tradition and radio isn't.
======================
I enjoyed the Scottish Microwave Round Table, and it was great to meet so many friendly and helpful people. I should be content but I am not. I cannot just throw money at a big linear for a band I hardly know. It might be a mistake not to buy the biggest boots I can find, but comfort counts in the boot world too.

I might be more comfortable with a small linear and make the same mistake as before. At least that will be simpler for me if I decide in a fit of pique to go QRT and adopt bear stuffing instead.

That is making stuffed toy bears, by the way.

Anyway, even if I do get into sewing and stuffing, I will always have the right transfer relay.

73
Jim
GM4FVM

Thursday, 31 October 2019

The joy of coincidence

Coincidence No. 1

Last weekend we reverted from Daylight Saving Time to GMT. It was GM4FVM's job to correct the clocks at FVM Towers. I did the heating clock, the shack analogue clock, etc. I couldn't do the clock on the oven as Mrs FVM was baking bread in it. I did the kitchen clock. I forgot the clock on the mantelpiece in the living room. I forgot one clock, just one.

Mrs FVM took  her time from the one in the living room, which was wrong (my fault). In the kitchen the kitchen clock decided to stop as soon as I corrected it due to a flat battery - coincidence 1. Just by chance, it stopped when I changed the time on it. The one on the oven just confirmed her view of the time - it was wrong because of the baking bread so I hadn't been able to change it yet.

So the FVM family tea had to be held an hour early, because everything had been prepared following clocks I hadn't fixed. Kitchen clocks that were stopped (I pointed out), or otherwise impossible to change by FVM, but he still gets the blame for those coincidences.

I tried to protest, pointing out that there is a clock in the kitchen on the radio which updates automatically, but then I was confronted with the evidence of the living room clock. Guilty!

Coincidence number 1a

Well, not really relevant to the radio blog, but I was on my way to see my ham pal "Gouda" at the garden centre tea shop the following day (what a crazy life I lead). I called in to get my hair cut by Chris the Barber in Duns. His clock was also still on BST - so not such a surprise at all really. This is just to show it isn't just me at fault. And radio amateurs do sometimes spend money on their appearance, despite what people say.

Coincidence number 2
What are the chances of these 2 drives failing at once? Or me misunderstanding the whole thing?


My shack computer has been suffering from over use. So I have replaced it. I might explain why and what with later, if anybody is interested. Or maybe I will explain someday even if nobody is interested.

As soon as I connected the backup drive to the new computer it failed. Exactly when I needed that drive, it failed. The click of death, that scourge of mechanical discs. What a mess coincidence number 2 was. Mind you, it did that once before and then it came back to life again later, but there is not much chance of that happening now, I thought.

I decided to use a different backup disk which had some of what I needed on it. Let us call the second one, backup disc 2.

Coincidence number 3

The new computer was acting up. It kept losing the USB sockets. I could not get through a complete backup without the transfer failing repeatedly.

I decided this must be due to a new 5 USB 3.0 socket extension card. However, I did have a 2 USB 3.0 one to try instead. I did not have enough of the right power sockets to run the only replacement I had and power the DVD drive at the same time so I decided to power the temporary extension card using a separate power supply. Could that cause some earthing problem? No, it seemed to work.

I climbed under the bench to try the sockets and suddenly there was a blue flash, followed by a loud bang and a nasty burning smell. I lay there and noticed that it was now dark, as the lights had gone off, and there was that sound of slowly stopping fans. I have described this sound before and it never leads to anything good.

Oh bother.

Please excuse the unparliamentary language. Jings, crivvens.

I had hoped that would be a nice new computer, but what have I done? Oh deary me.

Extricating myself from under the bench I found that I had blown the earth leakage circuit breaker on the main house fuse board, the switch fuse for the circuit covering the shack plus half the house, and the 10A fuse in my main "big switch" for the shack sockets. Probably I had blown the computer and everything else.

Having this blow loudly about six inches from my left ear made me a bit unsettled. Why had more than one fuse gone? Why the main earth leakage circuit breaker gone? Was this the earth fault I had feared?

It took me a while stop hunting for earth faults and remember that this had  happened before. One of those power supplies had blown in the same way a couple of years ago. Luckily that time I was not stretched out beside it. They are just cheap throw-away devices. So this was coincidence 3. I had decided to put my head right beside an exploding PSU, and it has decided to blow just as I did. And this had nothing at all to do with the USB extension board. Multiple coincidence.
This is the only one of three PSUs which hasn't blown ... so far.
After resetting the safety breakers and replacing the fuse, the computer powered up again.

But all the mains clocks had stopped and needed to be reset ...

Coincidence number 4

None of this solved the fact that the USB sockets still appeared to be failing. Connections to rigs kept stopping, my rotator boxes kept losing contact with their software, and all seemingly at random. It took a while for me to realise that it was not just that the second backup disc was failing as a result of the USBs going down, the second backup disc was causing the USBs to go down.

The second disc had decided to fail on the same day as the original backup disc, and even more puzzlingly, every time it went down it took the USB connections with it. Or at least the ones on the extension board. So that was coincidence 4.

It was easy to prove when I worked it out. Just introduce hastily thrown together backup disc 3, and everything was fine. So what are the odds of backup disc 1 and 2 failing at the same time? What are the chances of disc 2 having a fault that affected other USBs?

What are the chances of me completely missing the point and blaming myself?

I tried very hard to save that disc 2. I used AOMEI software to try to repartition it, format it, or whatever, but nothing worked. "Bad sector" stopped it whatever I did. Something is seriously wrong beyond bad sectors. I got the data off it by a three hour session of keeping pressing "retry" every time it failed.

So, when I stopped trying to use the second backup disc, the USBs all started to behave themselves. Then the postman delivered the cable I needed for the extension card and everything went back to normal.

Strange event number 1

Not exactly a coincidence, but after all this I tried the first backup disc again and it worked this time.

AARRRGGGHHH!

What a rigmarole. Certainly backup disc 2 would have proved to have failed whenever I tried it, but that would have been obvious if I was not trying to set up a new PC at the same time. I cannot trust the first disc but it is working again now. I spent ages with that extension board when there was nothing wrong with it, and my idea of an earth fault was just me trying to make sense of the temporary PSU blowing up spectacularly just when I decided to use it. Mind you, it had been sitting in a box for a couple of years, so blowing is not a real surprise - or so it looked when I calmed down.

When I was lurking under the bench in the dark, listening to the silence and smelling that awful burnt smell, I did wonder "why do I do all this?". I mean, here I am, in my sixties, stretched out on the floor in an awkward space, having just blown everything up (or so I thought). Will I ever mature and become one of those amateurs whose QRZ.com photo shows a clear desk, a rig and a microphone? Nothing ever blows for them, and their tea arrives on time in all time zones thanks to accurate clock regulation.

I would show you a photo of the blown power supply but I couldn't wait to throw it out. The photo above is the only one of three still working. No doubt it will blow soon too.

I have ordered a new case for a new backup drive (number 4), using a disc salvaged from an old machine. Maybe this is my problem, salvaging things and using them for years beyond their "use-by date". But hold on Jim, Backup discs 1 and 2, plus the PSU, were all bought new by me and are not salvaged at all.

Moral of the story?

Diversity and redundancy. Have two of everything. Or three. Then you can be totally mystified when they all break down together.

Or, to put this another way ...

If it can go wrong, it will. And it will go wrong just when you expect it not to.

73

Jim

GM4FVM

Sunday, 13 October 2019

What kind of a radio amateur am I anyway?

Aircraft scatter showing Doppler on G4RQI's signal on 4m. Curious? Interesting? Not in Ayton it isn't.

"Who do you speak to on that radio of yours anyway?" asked the neighbour.

Er, um.

How do I answer that one?

How do I define myself as a radio amateur?

I suppose they expect me to say "someone in Outer Mongolia". You know, somewhere exotic, where we might exchange cultural greetings and perhaps I could chat in my rusty but effective Outer Mongolian (which I have to confess, comes with an Ulster/Scots accent).

But, I do not really speak to anyone. Hmmm, maybe good old Gouda, with whom I exchange the odd word on 2m FM as our cars converge on the Garden Centre Tea Room. "I'm in the car park" - "I'll be with you in 2 minutes".

This does not seem to justify the eyesore which is my antenna farm, which the neighbour is balefully examining as we speak.

Hold on, I do use the microphone during contests. Yes, Eddie G0EHV, Jon GM4JTJ and David, G4ASR, every Tuesday or Thursday night. What if he then asks what we say to each other which is "You are 59 002 in IO85wu, 73". That hardly counts as a cultural exchange, and anyway these people are all in this great United Kingdom of ours (note: before posting this, check that the UK still exists). IO84 is not exotic.

That won't do for my sceptical neighbour.

Pretty much everything else I do is data.

I do not really talk to anyone. Sometimes the Postie calls with a Jiffy Bag from China with some BNC plugs in it and we compare notes between his guitar amplifier and my linear. All about harmonics, but not really radio chat. Once a year at the Galashiels Rally I meet ... well Gouda again. And maybe somebody else, you never know, like the man who prints out the callsign plates, or the chap selling the old valves (he never has the one I want, and I am never going to use it now anyway, even if he had it, which he doesn't).

The club? Aw, the club.  Half of them got fed up and the other half died.

Seriously, so many amateurs are passing away that we should be protected as an endangered species.

Harrumph. There isn't a simple answer to this. I am not in the business of talking to people on the radio. Sure, I used to be, but then I discovered the mobile phone, Skype, network radio etc. Back in 1974 the idea of talking to people in exotic places did really appeal. Not now.

Then, once I was licensed, I discovered that many of them would just tell you their name was Igor and they lived in Novosibirsk and that was it. You might improve your geography by finding out where Nizny Novgorod actually was, but how significant was that? You might even find the odd YU who would say something more than "rig home brew" like the other Easterners, but so what?

I am glad that these days people in Plovdiv, and Ulan Bator for that matter, have their own mobile phones, and are no more interested in talking to me by amateur radio than I am in talking to them. They have some freedom to talk now, and that is all for the good.

When you couldn't talk to people far away as an everyday event, then it had real interest. Now it just doesn't. We amateurs have to face it, the days when just the ability to talk to people was enough to keep up an interest in this hobby are long gone. Talking isn't the thing it was, and it certainly is not why I still follow this hobby.

Not that I am much of a home brewer either. As the years have gone on, that is an even lesser interest of mine. I admire those who do, and I often have discussions with them about that. Would my neighbour think more of me if I told him that? Probably not. This is the sort of neighbour who devours modern technology but who has no interest in what is inside it. Actually, all the other neighbours are the same.

No, I decide to answer along the lines that I am a curious radio amateur. I have suggested this on this blog before. I'll explain the fascination I have for it all and he will be impressed by that.

It went something like...

"I don't really talk to people on the radio these days, I tend to use computers". He now has a far-away look in his eyes. "For instance I can bounce signals off meteors, or the ionosphere, or even the moon".

He has accepted that I am not talking to actual people by radio - he now thinks I am sending emails to The Man in the Moon.

He takes a moment to absorb this remarkable fact I didn't tell him.

"Well, you have put up a bigger aerial to do it". He says.

I haven't. I think he is getting confused as my antennas now are smaller than they have been for years.

I reply "You probably just saw them side on, which is longer than end on" I am trying to explain the Yagi in this way, but he seems to be losing interest.

"Eh?" is his inspired response. Could this be curiosity in him ? (no Jim, get real)

"They turn you know. I rotate them ..." I can see that his eyes have glazed over again. I tail off trying to explain the concept of a directional antenna.

"Aye, well ... " he says, and then he turns and stomps off to go back to raking up his leaves.

That went well.

I am glad that the community appreciates my particular take on amateur radio.

Curious, that's me.

And the rest of them? They aren't curious, at least not when they find out I do not actually speak to anybody.

The scary thing is that they all have a vote.

73

Jim

GM4FVM

Thursday, 3 October 2019

Icom IC-9700 operational review.

Please forgive me if I have forgotten anything or if I get anything wrong, there is a lot to cover with this thing. I will correct as necessary.

I find it hard to know where to pitch my review of the IC-9700.
IC-9700 at GM4FVM in single receiver mode.

There are quite a few reviews on the Internet. Many of these seem to come from either retailers who want to sell you one, or those "opening the box" type articles. Both of these seem to have missed the point when it comes to actually using the thing, which is where I am trying to pitch this posting.

There are also some reviews which seem to originate from one individual who appears to have a very cosy relationship with Icom. I have no relationship with Icom other than as a customer. I am not an Icom fan, and the only reason I have Icom equipment is that it seems to meet my needs in certain areas. If anybody else made something suitable, then I would try that. Over the years I have had Yaesu, Kenwood, Flex, ... you name it. I am what the marketers call a "brand tart", someone who has no brand loyalty. Why should I be loyal to them?

I should say early on that I do not use amateur satellites or DStar digital voice mode. I cannot test this radio for those uses and therefore if that is your main interest maybe some other review would be better for you.

1: So what is it?
The IC-9700 is a multi mode (FM, SSB, CW, AM, DStar DV, various data), three band (2m, 70cms, 23cms), transceiver using mostly software defined radio techniques.

I am not going to try to set out a technical review. Not only do I not have enough test equipment, but also it has been done elsewhere. There was a four page review in the RSGB magazine Rad Com in September 2019. That was fairly soul-less, but it has the data in it, so look at that if you need the hard facts.

A much better review for an operator to consider would be this one which appeared in Practical Wireless magazine:-
 https://www.radioenthusiast.co.uk/articles/review-icom-ic-9700-vhf-uhf-transceiver/
Note that the review at the above link was written before the firmware update which allowed the 10MHz frequency standard input to automatically control the frequency and thus resolve the drift issue. 

This article correctly pointed out that I might not understand the full implications of the Nyquist frequency. For a Software Defined Radio ("SDR") like the IC-9700 or the IC-7300, I understood that the Nyquist frequency was twice the highest operating frequency - so in the case of a radio covering up to 52MHz this would be at least 104MHz. that would mean that the clock in the sampling oscillator would need to run at at least 104MHz. It is possible to go slightly beyond the Nyquist limit, in other words, to operate the radio beyond half the clock sampling frequency but at reduced efficiency, a fact which the IC-7300 uses to cover up to 72MHz in European models.

So, with the difficulty of getting stable oscillators at a reasonable (amateur) price beyond a couple of hundred megahertz, difficulty which increases the higher you need to go, it seemed to me that there was no prospect of an amateur VHF SDR in the near future. But I was just ignorant of the facts (not for the first time, Jim). As G4DDK explains in his review, you only need to raise the clock frequency high enough to cover the range of frequencies the radio operates at, not the absolute frequency. So the trick used by Icom is to offer the IC-9700 without general coverage between the amateur bands. This reduces the ranges to 2MHz (for 2m), 10MHz (for 70cm) and 30MHz (for 23cms), which can all be covered by a clock oscillator speed similar to a standard HF radio.

2: The benefits of being an SDR...
The general idea behind an SDR is that most of the processes inside the radio are defined in software, which means that you can change them at will. There are of course some things that Icom will reserve to themselves, and which you cannot change - this is to meet their regulatory requirements, or for commercial reasons about not letting their secrets out. How easy it is to change these things is something which Icom seem to be getting good at. With the arrival of the IC-7300, and further developed in later rigs, the touch sensitive screen is exploited to make changing those many aspects easier.
The main display on the IC-9700, single RX, spectrum scope showing +-100kHz

For a simple example, take mic gain. Suppose you want to change it. You just have to press the "Multi" button and up on the screen comes a display showing RF Power as well as Mic Gain (showing the current level of Mic Gain, 38%, as I write this).
IC-9700 display showing mic gain level ready to be altered

The clever thing then is that you just press the Mic Gain area showing on the screen, it is highlighted, and then turning the Multi control will alter the Mic Gain. I can raise it or lower it. This is very user-friendly. You don't have to plough through menus - when Mic Gain is showing all you do it highlight it and you can change it. The same knob (Multi) selects the display - push - as changes the level - turn. Very sensible ergonomically.

And this approach extends to the more complex settings. Sure, as you get further away from the few settings you use all the time (Mic Level, RF Power etc) you move into some menus. However, these are easier to navigate thanks to the touch screen. Pass band tuning, for example, it shown up graphically on the touch screen by pressing the "PBT" button.
IC-9700 PBT display ("Pass band tuning").

You can then see the exact alignment of the pass band tuning filters. If you then press the display on the filter area and turn the Multi button, not only do you move the passband filter, but you can see the result immediately on the screen.
Adjusting IC-9700 PBT filters
The display shows the central area of the filters, showing how wide you have set it, shows in figures the bandwidth (2.25kHz) and the offset (+375Hz). Also shown is a white dot to remind you that passband tuning is offset (handy if the offset is low) - if you want to cancel your settings just press and hold Multi and the two filters return to full overlap, the dot disappears, and normal filtering is resumed.

What I am trying to get over here is how simple the process is to use and how natural it all appears to the operator. In reality, at the heart of the SDR, there is no pass band tuning in hardware sense. You are looking at a representation of two filters, and the radio behaves as if there are two filters, but the whole thing is done in software.  To the operator, you get the display, and you do not need to worry about how it is done.

This approach is common in SDRs, but with the IC-9700 the ease with which you interact with the radio has been brought to a high level of simplicity. The buttons, the knobs and the display all work together seemlessly. My Flex 1500, which had similar features required a lot of fiddling with the computer to access them - with the IC-9700 a radio with knobs and displays working in an integrated way is vastly more user friendly.

To take another example, but one which I will not illustrate, we could discuss the notch filter. Press the dedicated button "Notch" once and the display shows the message "AN" (automatic notch). Press it again and you see "MN" for manual notch, and in my case also "NAR" meaning narrow. Press and hold the Notch button and a familiar bar display appears at the right hand side of the screen - rather like the one for RF Power and Mic Gain, but this time showing Notch - Position and Width. With the Position highlighted turning the Multi knob moves the notch filter and also moves the graphical representation of the notch. This means that you can see the notch in your passband and move it accordingly. Touching "Width" on the right hand side display cycles between Narrow, Mid or Wide notch. You can adjust that and then press the bottom of the screen to return to normal display.

I find this notch adjustment very useful indeed. Sometimes on VHF some very strong local signal will appear inside the data mode passband of my receiver. In narrow setting I can notch it out. Not only can I hear the effect of the notch, I can see on the display where the notch is. It might seem obvious, but somebody has spent time making the interface so naturally user-friendly that it just disappears from the operator's consciousness.

Another aspect of SDR is the ability to alter the characteristics of the filters themselves. We have been able to use radios with digital signal processing for several years. This has allowed us to have digital filters like this for some time. But now with (more or less) fully SDR radios like the IC-9700 the whole filtering processs is done in software which is integrated with the entire signal path. At the same time, the complexity of the software has developed to the stage that we are not just turning things on or off, but can change almost every aspect of them on the radio itself and not via an attached computer.

Not only can we alter the notch and the filter width, we can alter the slope of the filter edges. The IC-9700 allows you to choose between "soft" and "sharp" filtering. How simpler could it be? Just press the screen on the FIL (filter 1 in my case) and up comes a screen showing the filter in use and you can change between filters and sharp versus soft. Not only is that set for the settings you are using, but there are different settings available, for mode. In my case, FIL1 is set for 3.0kHz soft for data (USB-DATA mode) and 2.4kHz sharp for SSB (USB mode), and the filters change as necessary as I change mode.
IC-9700 filter settings for data ("SSB-D") for filter 1 (FIL1)

Why would I want to change between soft and sharp, or one filter and another? Well, between data and voice in my case. And the IC-9700 will remember that choice on each band and switch between. So  you customise each of the three filters and select which one to use on any band and mode. Actually, I prefer soft, generally, but I do use 3.0kHz on data and 2.4kHz on SSB. Set it up and forget it because the 9700 does the remembering.

Lest we forget how far we have come here, buying a radio used to involve working out which filter we would be likely to need, and then buying it as an expensive add-on. You might only have room for one more (with the FT-817 you choice was very limited). Needless to say, you got somebody else's idea of whether you needed soft or sharp filtering. I remember buying an expensive CW filter for my FT101 (+ 2m transverter), and an equally pricey "SSB" filter for my FT-817 to use with data modes. Now with this IC-9700 I have a wide range of filters which are easily configured and structured seemlessly into the digital structure of the radio. Not only can you configure lots of settings, but you can often see on the screen exactly what you are doing. SDRs are now delivering the ability to be customised we were promised, in a single box VHF/UHF rig, and in a seemless, user friendly, way.

You have even more choice on the PBT front too. There are, in fact, two Pass Band Tuners to choose from - PBT1 and PBT2. You can customise them and select between them.

The layout of buttons and knobs on the IC-9700 is similar to the IC-7300. Most of the functions are similar too. However, to cope with the fact that the IC-9700 has two separate receivers some changes have had to be made. The IC-7300 has a dedicated pass band tuning control, whereas on the IC-9700 there is a PBT button and after that you use the multi button instead. That is the only drawback I can see to the different layout - and maybe many users never alter the PBT. Also, as there is no auto tuner in the IC-9700, that button is used for CALL/DR for DStar.

So you have buttons for Power, Transmit, Call/DR, VOX/Bk-In, PreAmp/Att, Notch, Noise Blanker, Noise Reduction, Menu, Function, M. Scope (shuttles display settings), Quick (often used settings) Exit, RIT, kHz/M-Ch, Split, A/B (VFO), VFO/Memory, Scan, Tone/Rx-CS, Memory Pad, AFC/Auto Tune, Speech/Lock. I hope I have made these as self-explanatory as I can as it would take an age to define them all. The basic manual is 96 pages and the advanced manual is 173 pages, and I am not about to repeat all that here.

The knobs are for
1) Main: AF, RF/Sql (concentric), select main/sub (press),
2 Sub: AF,RF/Sql, (concentric), sub on/off (press)
3) Multi (turn) Clear (press)/
4) VFO
Obviously the touch screen can be used for many things, often after the appropriate button has been pressed to activate changes.

With that array of buttons and knobs you can see that you have a wide array of things to keep you busy. As I have been droning on about, during the early implementation of amateur SDRs a lot of this was only alterable using the attached computer, whereas the IC-9700 can operate as a free standing radio. You can alter just about everything you need in settings and leave the computer (if you use one) to run data software.

The wheel has gone full circle. That Flex 1500 I keep talking about had one switch - on/off - and everything else was adjusted in the computer. The Icom IC-9700 has all the switches and knobs you are likely to need. The designers of those early SDRs thought we would enjoy using our computers to access the rig, but we amateurs thought differently. Now Flex sell (expensive) computers to act as front panels for their radios. Perhaps they forgot how important human/ machine interfaces are to our construction of a meaningful operating environment. To sum up - we wanted the knobs back. So radios become more like computers, and took back the processing from the PC, and better chips and technology helped that along.

You only have to look at the IC-9700 and its great big VFO knob to see that the designers of SDRs have got the message. As Kenneth Horne often said in "Round the Horne", there is nothing quite as satisfying as a great big knob. Or he said something like that anyway.

And finally, a key advantage of an SDR is that the nice folk at Icom can make available firmware updates to fix any glitches which come to light. This means that the old way (if you bought an early rig you bought problems which were fixed for those who bought later ones) should be abandoned, and our expensive radios should be upgradeable. And so it proves (see later).

3: .. and how is it not totally an SDR after all.
For all the SDR credentials the IC-9700 has, it is not entirely an SDR. In perfect form, an SDR would convert incoming RF at the earliest stage into digital information, then process it as a digital data stream before either converting it back to analogue for output on a loudspeaker or shipping it off as a data stream to be decoded as FT8 or whatever in our computers. And the reverse would happen on transmit.

The IC-9700 meets that ideal in most respects, but not on the 23cms band. In the case of 23cms there is an intermediate frequency at 311-371MHz (for the European model, varies for other markets). So in that case the radio does not convert to digital directly at 23cms, but in the IF range. Am I bovvered? No. It is a little bit of superhetrodyne- type twiddling to allow a radio to cover the three bands, and seems logical to me.

It is a bit as if we are using an SDR to tune the IF produced by a transverter. Ignoring the fact that this is also like the execrable Liner 2 (with a CB radio rather than an SDR in that case, but the same idea to extend a simpler transceiver to a higher frequency range without having to complicate the basic rig), why not? If we have to wait for SDR technology to make the whole radio general coverage from DC to 1300MHz, plus make it affordable, it will take a while. There have to be some trade-offs, and I can accept losing general coverage and full-SDR ability to give me something which works.

Not quite being a full SDR is a fact, but not a very significant one to me.

Incidentally, before I had the IC-9700 I was using an IC-7300 and a transverter on the 2m band. This was a great combination. Now I have the IC-9700. I took out the IC-7300 and slotted in the IC-9700. For a while I used the 9700 only on 2m. Frankly, I hardly noticed the difference in operating terms. Tuning a transverter with an SDR might not be technically perfect, but it was better for me than tuning a transverter with a superhet.

4: Issues
Issues are things which are not problems, just irritants, things to get used to, etc. Things that bug me about this radio.

As I said, changing over from the IC-7300 and transverter combination to the IC-9700 went almost un-noticed. The low-noise quality of the SDR all- the- way showed through.

The biggest issue from an operational point of view was, oddly, the second receiver. What seems like an unqualified benefit actually worked out a bit hard to get used to.

I am something of a dinosaur with radios. Rather than use expensive ones with multiple receivers, I have used two simpler radios which just had one receiver each.

Now I have an IC-9700 which has two receivers. To shoe-horn the two receiver details onto the display, the Icom designers have to let something go somewhere.
IC-9700 display with both receiver turned on.

When you are using both receivers you get to two frequencies displayed on the screen. You can select either VFO (in which case the other is greyed out) and change the frequency for that one using the VFO knob. You can only transmit on the main one - the top one.

So let us say that I am listening to the GB3NGI beacons on 144.482 and 1296.905. Both beacons can be heard because each receiver has its own audio gain control. You can switch the VFOs between the "main" receiver (top) and the "sub" receiver (bottom) just by pressing the top AF control (marked M/S) for 1 second.

Switching between main and sub (or rather swopping the VFO frequencies between them), is handy for, say, when you are monitoring another band and decide you want to go there and call somebody. Not beacons of course, but other stations.

Only the top frequency is sent to the digital output on the USB lead. Although I can hear the 1296 beacon on the loudspeaker, I cannot decode the data via the USB lead because it is on the sub band. If I switch over between the main and sub then the other one cannot be decoded via the USB lead.

There are two COM ports created when you plug the USB lead into a computer, but the second one is for GPS data to be used with DStar digital voice mode.

I think I can see a work-around for data-mode users to get the data stream out from the sub receiver. There is an audio output on the back panel via a 3.5mm socket which could be used to route analogue output to the computer. However, there is no "CAT" type output from the sub VFO, so that would have to be done manually and if you switched between main and sub it would require manual updating.

I wasn't really expecting a two receiver radio to allow separate data output and CAT control of sub-bands, though I believe that the ELAD FDM-DUO does (with up to 9 receivers!!!). So I am not too disappointed with this. It would be VERY handy to have. After all, in these data-mode days it is hardly surprising that we might like to decode signals as well as listen to them.

So that is an issue but not really a big thing for me. Neither is the fact that you cannot run the two receivers on the same band. It might be very handy during a contest to leave one receiver on a station who is busy working others, and then listen to them in the background while you pursue other DX until you can call in. Sure, you can do that by putting the frequency into VFO A while working on VFO B, and then switch between them. However, you switch between, you cannot listen on two frequencies within the same band.

I see that issue, but it is not a deal breaker for me.

A spin off from not being able to set the same frequency band on both receivers is that when you have both receivers working you cannot, say, leave the main receiver decoding 2m FT8, go to 1296 to listen on the sub, and then nip across to check something on the 2m band on the sub receiver. As only the main receiver outputs data, you cannot swap that with the sub without losing the data stream.

If you don't use data modes most of these issues do not pose major problems. But only having one data stream out, and only allowing the two receivers to operate on different bands, can produce the need to apply weird patterns of juggling between VFOs and receivers to sort things out.

The band stacking register is very clearly displayed, which is great. You use the band stacking register to change band, and this initially struck me as odd. It works, and if you have both receivers turned on it shows which band option you cannot chose - whatever band is in use by the other receiver is greyed out. If you want to use that band with your current receiver then you have to juggle them around.
IC-9700 Band stacking register
I am not expecting to use the two receiver capability much. So far I have been using the IC-9700 as a single receiver rig switched between two bands - 2m and 23cms. I usually have the second receiver turned off. That way the operating frequency always follows the instructions from WSJT-X. Also, there is just one frequency on the display, which eases the strain on the tiny processing capacity which remains operational in my brain.

I am sure that in the long run I will get the hang of the dual receiver function, but right now it just gets in the way.

Why did this radio appear with an SO-239 socket on the 144MHz RF output (in Europe at least)? I keep having to spend £10 to buy new sockets as the 2-hole ones are hard to find at a decent price. Grrr, that's my issue for sure.

Finally, an issue I am not so sure is really an issue. There is a facility to turn on a DC voltage to power a mast-head amplifier, customisable to any combination of the three RF outputs for each band. I cannot work out if, or how much, this is sequenced to the PTT operation. The manual does not seem to explain. I guess it must be as otherwise I usually get a momentary high-SWR as the RF VOX in the preamp works. Properly sequenced DC bias causes no SWR problems and I have no SWR problems. But why does the manual not clear that up? I'll need to measure it to satisfy myself.. 

5. Problems.
For me there were two main problems with the IC-9700 when it arrived. One is the frequency stability, and the second is the single push to talk output.

Dealing first with frequency stability, this has been well covered elsewhere in the specialist magazines and the internet. It was widely reported that on receive things were fine, but if the rig was used to transmit long enough for it to warm up and the thermostatically controlled fan come on, then it drifted quite significantly. Quite significantly means too much for WSPR decoding, but then not many of us use WSPR on VHF.

I have made a separate posting about this problem here. Basically, I added a Leo Bodnar GPS disciplined frequency standard and the problem (if there was a problem) went away at a cost of £100.

There is a lot of complaint on the Internet about this problem. True, Icom should have discovered it before the radio was released, and also true they should have offered the solution much more quickly. But the solution now exists (thanks to a firmware update), so we should move on.

Secondly, the IC-9700 has only one PTT output on the accessory plug for linear amplifier control. This is a big surprise for a three band VHF/UHF radio as there is no practical option for one linear to cover all three bands. It is a baffling error for Icom to make, as earlier Icoms covering these bands had provision for at least two PTT outputs. I wrote about this here.
Rear view of IC-9700 - no room on ACC socket for multiple PTTs (Icom Brochure)

So concerned was I that I decided not to buy an IC-9700 until I could find some resolution. As it turned out, an IC-9700 arrived anyway so now I will need to resolve it myself. I worked out a way of avoiding any potential damage to my mast head pre-amps by simply turning all of them off when transmitting on any of the three bands. That solves that problem but it is not practical for the linear amplifiers. Switching a linear to TX when there is no RF signal on the input opens (in my mind anyway) the door to self-oscillation in the linear. It is not good practice in my book.

I see on the internet that at least one other amateur has thought about reading the CI-V line and switching the PTT that way. I must contact them and ask how they are getting along. In the meantime, the single PTT configuration remains a problem for me.

6. Using it
Nothing adverse to report here, apart from the issues and problems reported above. The HM-219 hand microphone gets favourable reports. The large VFO knob with the freely rotating finger cup is a nice feature. The colour display looks great, but there is not much room for the waterfall when both receivers are switched on. There is no socket for plugging in a bigger display.

Knobs and switches are generally well laid out and easy to use. As with the IC-7300, the buttons under the upper dual AF/RF controls (P.AMP.ATT and NOTCH) are difficult for me to see. Perhaps my shack illumination needs to be mounted lower down.

Speaking of those dual AF/RF level controls, it is a pity that adding the Sub AF/RF controls on the 9700 rules out the inclusion of separate PBT controls as on the IC-7300. I guess there is no room, and you cannot have everything. As I usually keep the second RX turned off, those controls are out of use most of the time. Ah well.

I have used the IC-9700 on SSB and data modes on all three bands. I have gone onto RSGB UKAC contests with SSB on all three bands. The radio performed just as I would have expected - well. The receiver is quiet and the ease with which you can adjust the filters is a joy. Well, the ease with which you can adjust anything is a joy. The flow of the process from finding the function to altering it while seeing what you are doing is an exemplary model in ergonomics.

Having a radio which is very easy to handle is all well and good. Is it top in its class for performance? As this is not a technical review I cannot say for sure. The test for me will be moonbounce performance. Of all the modes and bands I use, only EME really tests my equipment to exacting standards. On 144MHz I have heard stations via EME using the IC-9700 and I have been heard via EME. Clearly it is stable enough and sensitive, but I have not yet had an EME QSO with it.

This is a pretty sterile debate as EME conditions are so variable and open to many interpretions. My set-up has marginal performance as a moonbounce station. I am always relying on good stations at the other end, due to my (self-imposed) limits on antennas and power output. Ask me for a subjective opinion based on too short an operating period and I would say that the IC-7300/ME2T-Pro transverter combination is slightly better than the IC-9700 when it comes to sensitivity. With the GPS frequency standard connected, the IC-9700 is better for frequency stability - and everything else.

There might be 1dB in it, if anything at all. The benefit of having the whole thing in one box, and rock steady in frequency terms, leads me to prefer to IC-9700 over the transverter set-up. We should not forget that my transverter drifts a bit too.

We shall see in the long term, and for now I still have the transverter, because I think it is, very very slightly, better at the very edge of weak signal performance.

On the other hand, if I got a good offer for the transverter I would probably give it up and go 100% for the IC-9700.

7. Conclusion
I like it.

If I had been spending £1800 of my own money I doubt if I would have one yet. I had decided to wait for a resolution of the single PTT problem. Somebody will crack that someday. In the meantime the problem still isn't resolved, I am using the IC-9700, and I like it. Make of that what you will.

The radio closest in specification to the IC-9700 I have used was the Icom IC-910. That was ten years ago in superhet days. It had the 23cm unit installed but not the optional digital audio processing unit. I think from memory that the digital audio processor worked at audio frequencies and was not operational at RF. Anyway, it sounded very noisy on receive. From an operational perspective the IC-910 seems like a generation ago rather than ten years. It was hard work to adjust anything, you just had to take what you were given. The IC-9700 is a huge leap forward compared to that radio.

I have a (sort of) feeling that the IC-9700 is not the end of the line for Icom VHF/UHF offerings. I might be wrong here! Sure they will be busy launching the IC-705. But I sense another rig on the horizon. This is an SDR featuring the broad outline of the HF abilities of IC-7610 married to the high band ability of the IC-9700. Something like an Kenwood TS-2000 but this time with a sensitive receiver and also being an SDR - or a Yaesu FT847 that worked and was an SDR too. This would be expensive, but the problems of building the 9700 down to the £1800 price tag would be lifted. It would have two or three PTT outputs customisable by band, it would have a built in GPS standard, it will have the ability to have both receivers on the same band, both receivers will have CAT control and USB data output for each, there would be a separate PBT control ... and I for one won't pay the extra money.

Possibly.

In the meantime we have to IC-9700, which seems pretty good to me.

73

Jim

GM4FVM

Tuesday, 1 October 2019

Icom IC-9700 drift solved with GPS frequency standard

I have almost finished my IC-9700 review (well a review of the operation of the radio if not the technology), but the section on the frequency issue was getting so big I have decided to split it off into a separate posting.

EDIT - the IC-9700 review is now here.

As regular readers will know, I like a bit of drama and mystery. Having been brought up on cop dramas in the "Dixon of Dock Green" style, to begin with I never really had much to work out. You could see who did it, and the writers went out of their way to assume that you were an idiot who needed all the obvious clues pasted in front of you for 30 solid boring minutes.

We will never know how bad it all was, as of 432 episodes of Dixon made between 1955 and 1976, 400 are missing. I wonder why.
Jack Warner as Dixon of Dock Green (Photo wikimedia)
Then along came Steven Bochco with Hill Street Blues and everything changed. Here the audience were assumed to be reasonably intelligent and could be trusted to work out what was happening. The plots could emerge over weeks rather than 30 minutes. Once I recall noticing a man on a horse appearing in the background of the crimes, who the cops didn't even spot. Weeks later, the link was made, but during that time I thought I was the only person who had the clues. Suddenly it was personal, and I liked it.

And after that it moved on to NYPD Blue and others took up the idea so that we have plots to resolve over weeks and series that last for years. Then there is Vera, which while every episode is complete in itself, has the peculiar distinction of having all its bodies found near GM4FVM. Mystery indeed. What is the link between all these murders and this place?

Vera has been filming at Burnmouth lately but I doubt if you can see FVM's antennas in the background unless they used a helicopter shot. 

Vera isn't really on a par with Hill Street Blues of course. The biggest mystery about Vera is how come a 73-year-old can still be a murder detective? There is hope for career development for me yet - if Brenda Blethyn can do it, why can't I? (Because she can act, Jim)

That was cruel. Jack Warner was over 80 when Dixon finally retired from the force. "Take me with you, I can see" (it worked for Donald Pleasance - well for a while it did anyway).

So where is all this going? Well, this posting is like an episode of Columbo (Bochco briefly wrote for Columbo). The thing about Columbo was that you knew who did it all along. There was no mystery in that sense, you just needed to know how he worked it out.

Plot summary - The Icom IC-7900 is suspected of drifting as the cooling fan turns on and off. Adding a GPS disciplined frequency source stops it drifting. Erm, That's it. All that remains is to work out how Columbo solved the problem.

Nothing to see here. Just stay behind the Police tape and move along please.

Well, there is one mystery to be revealed. "Just one more thing" as Columbo might say. Is drift a problem? Could it be that just one or two samples of the IC-9700 were a bit drifty and those owners went on the Internet and the rest is history?

Probably.

My initial tests on 2m suggested that my normal usage never brought the fan on anyway. Maybe that is because I only run 25 watts out on 2m, and 10W on 23cms. So I did more checks.

There are two aspects to this -
1) is the frequency readout accurate to start with?
2) does the radio stay on that frequency?
So, for example, my IC-7100 routinely starts showing a 70cms GPS-locked beacon on the wrong frequency (often 100hz out), but stays rock steady on that frequency for the rest of the session.

And then again, does a few Hertz drift matter? Does being slightly off matter either? Well, yes, it does for me. I want to find weak beacons, so I need to be looking in the right place. And I use data modes, some of which are fussy about stability. So let us see what the TV audience thinks.

I used the GB3NGI GPS-locked beacon for my tests. It had been working a bit erratically recently but it seems to have settled down lately.

Taking 23cms first as that is where I expected most drift ...
GB3NGI at GM4FVM on 1296.9042. Mark and space CW ident can both be seen drifting (H scale hz, V minutes)
Monitoring a beacon 272km away on 23cms is bound to introduce some squiggles as aircraft pass and the troposphere gurgles about, but I think this shows the general picture. The rig had been running for about an hour before I started measuring. Over 20 minutes it drifted 57hz. Whether you think that is important enough to worry about depends on your viewpoint. Certainly the JT4G decoded most times.

At the start of the 20 minutes the readout was 19hz high, and it ended 38hz low (or it would have been had I used a zero beat method).

I thought about this two ways. One, these results are on receive, whereas the reports of problematical drift are as the cooling fan turns on and off during long transmissions. And secondly, am I going to miss a beacon by looking 38hz off frequency?

In the end I resolved it this way. This is a rig valued at £1800. The frequency standard might cost anywhere from £25 to £100. Surely it is worth fixing.

Here is what happened when I turned on the frequency standard...
GB3NGI at the point of turning on the GPS from cold - note the jump in frequency

As the GPS standard was starting from cold it would take time to lock onto satellite signals (not very long actually), plus it would then need to discipline its crystal oscillator to bring it to 10MHz. It did not find the right frequency immediately.

To begin with it dropped 57hz, which was 19hz low. Then over the next 2 minutes it moved back towards the correct figure (800hz on the waterfall).

After that I ran it for 2 hours. At no stage did it vary more than 2hz from the expected point 800hz.

Rather than drifting at about 3hz a minute in one direction, it settled down to jogging 2hz around a single point, and it stayed in that frequency range for 2 hours and the frequency readout was perfectly accurate.
Under GPS synchronisation, hours of steadiness with just some aircraft scatter for variety.
For comparison, the drift at 2m was hardly measurable on receive although turning on the GPS made the IC-9700s frequency readout accurate - by moving the radio 35hz. Hardly as significant as 23cm because it seemed perfectly stable even if it was wrong. I can stand being a few hz out but I detest drift.


So there is your Columbo start. No surprise here. We know who committed the crime. Icom by sending out a rig with a fan blowing on the oscillator, without automatic GPS synch input, and then taking ages to upgrade the firmware. The GPS standard works perfectly. You know what happened. Justice has been served. But how was the crime solved?

I bought a Leo Bodnar GPS frequency standard, set it to 10MHz and lowest output level, added a 20dB attenuator to produce the right level for the 9700 (-10dBm approx), and ... well, off it went. Problem solved (not that there was a major problem, but I might have found one later if the fan ever turns itself on).

To start synchronising you need to find "REF ADJUST", by pressing Menu, Set, Function, and then open REF Adjust.


As originally supplied, the first IC-9700s could not use the 10MHz frequency standard to automatically reset the frequency - you could input the frequency but you had to make the adjustments manually. Now after the latest firmware update this works automatically.

At some stage I found out how regularly the synch was done, but either I forgot, or I couldn't be bothered to remember. Either way, this information is not currently available on this site. It synchs often enough to work, I think.

Press "Synch to REF IN". Then:-


"Start". And then for a few seconds this
... and finally ...
Success. You can find pages of bile on the internet about how to get round the reported frequency instability, but once Icom issued this firmware update this resolution became available.That made all the agony irrelevant, though I think Icom should be criticised for putting us all through the misery of waiting for this.

With regular reference to the GPS standard at my end I now find that GPS-linked beacons appear exactly where I expect them to.

It is worth remembering that GPS disciplined sources like this have a TXCO inside. In other words they are a good crystal oscillator, and then they use the GPS signal to fine tune their on-board crystal oscillator. So if you lose the GPS signal, through a fault in your GPS antenna or whatever, the oscillator will continue to function on its own at the specified frequency. Once GPS reception is restored the accuracy will return to GPS standard.

A few points arise at this point. Firstly you do not need to use a Leo Bodnar unit as I did. Jan, OZ9QV, contacted me about the RFzero unit. I looked carefully into this and it seems like a very good item and I would encourage anyone to consider it. My choice was for the Leo Bodnar was for a non-radio reason. Or at least non-technical reason. I have nothing against the RFzero, just that the Leo Bodnar was bought for a personal reason. It cost £100. They do a buffered two output one too, but that costs more. I would have liked the dual output one, but I know I have no real reason to have one.


Secondly, I could have used my Trimble Thunderbolt, which I see others have done. Apparently it works according to reports, but I wanted to keep the Thundbolt for providing PC clock synchronisation for that portable data-mode operation I will someday do outside wi-fi range. You know, that portable operation which I have never done.

Thirdly, while the Leo Bodnar has a USB plug which provides power and a data connection, with my set-up this cannot come via my PC. The way my system here works, everything is isolated from the mains power using "the big switch" method. I turn the big switch on which starts the rigs. The computer is powered up but it does not start until I press the button on the front. If the computer was then powering the GPS, the 9700 would have lost synchronisation as it had started before the frequency standard. You do get a warning about this
I know I am old-fashioned, but after sitting through all those ergonomics or "man-machine interface" lectures, as we called them in those days, I hate seeing warnings regularly. Warnings are to tell you something is not right. You should take action on them.

To eliminate this warning I simply powered the GPS reference via a separate power supply which comes on at the same time as the radio. My PC, which is started later, does not power it. The drawback to that is that I would need to unplug the GPS and plug it into the PC if I needed to change the reference output frequency - something I have no plans to do.


I know as I write this that somebody will criticise me for leaving the radios on and letting the big switch do the on/off role. Sure, there is potential for a fault in the power supplies as they come on and off which might damage the radios. However, this has not happened yet. Well, a power supply did go bang once, but no damage was done (to the radios ...). My angle on this is that keeping the big switch off is more important, but I might be wrong about that. Having too complex a shut-down routine will probably mean I will just forget to do it.

Turning briefly to the Leo Bodnar GPS standard...
Leo Bodnar GPS frequency standard with a Danish Krone for scale
Maybe I might have chosen a different scale object. OK, let us just say that you can judge how small the thing is from the SMA socket on the left hand side. That socket is for the supplied GPS antenna which is equally tiny. I took the GPS antenna, thinking it would need to be placed in the loft or even outside, but temporarily stuck it to a metal shelf inside the shack (it is magnetic). I had GPS lock within seconds, even with all the RF floating around in here.

You set the reference output frequency using very simple software. I imagined the set-up would be difficult, after setting up the Trimble Thunderbolt years ago. The Trimble only has a fixed 10MHz output (plus loads of harmonics of course). The Leo Bodnar standard was simple to set up by comparison. With a huge range of available frequencies the Leo Bodnar must have many uses around the shack.

Conclusion
1) the drift on the IC-9700 was there on 23cms but not a big issue on receive.
2) firmware updates allow GPS synchronisation so why not do it?
3) as well as stopping the drift, the frequency readout becomes dead accurate - turn it on each morning and it comes on at the same frequency every time
4) the GPS frequency standard unit is great and it will find lots more uses

Was the drift bad enough to worry about? Probably not. But it certainly is not worrying me now.

At the end of Dixon of Dock Green, the man himself stood on the steps of Dock Green nick and gave a little homily to the audience at home about bad people getting their come-uppance and good folk having nothing to fear. This always stuck me as odd, because even as a child I knew he couldn't address me personally as he was a fictional character acted out in front of a TV camera by a dozy old actor 500 miles away.

I should give a similar homily now but, looking out at the world in 2019, I don't think you would believe me that we good folk have nothing to fear.

"Evening all."

73
Jim
GM4FVM