Monday, 20 May 2019

Feeling jaded, plus antenna planning permission in Portugal

"When a man is tired of radio, he is tired of life, for in radio there is all that life can afford."

A comment attributed to Dr Samuel Johnson (1707 to 1784). Well, he might have written it had radio been known in the Eighteenth Century.

I think he may have been thinking about radio when he referred to London. Most things I hear seem to relate to radio.

Oh dear, am I becoming radio-obsessed?

Surely not.

I have been feeling out of sorts. As I have said before on this blog, I have a love/hate relationship with radio. Sometimes I cannot get enough of it, and then minutes later I want to give it all up, go QRT and take up quilting instead. Making quilts seems like a more restful hobby.

Usually some challenge will make me perk up. I have several challenges underway right now, for example two projects to improve the performance of my 2m and 70cms stations. These are also part of the "simplification" strategy which seems to involve getting more gear, but anyway ....

For some reason all these plans have failed to lift my gloom. Perhaps a break away would help. Mrs FVM was also enduring a bout of indecision. Hers was in case we might go away and find that Brexit had been resolved while we were away and we found ourselves locked out of the country when we tried to return. However, as it became clear that waiting for Brexit to resolve might take longer than the Summer (not saying which year) she decided to take me to Portugal for a week, with some help from the fine people at Jet2.

All this lack of enthusiasm for radio brought about a ground breaking decision. For the first time in my life I would leave these islands for a holiday without a radio. OK, I know my phone is a radio, as is the wi-fi on my tablet computer, but you know what I mean. The faithful Roberts stayed stored away at FVM Towers. This was to be a radio-free holiday.

After a 03:00 start from a cheap hotel in the Northumberland tourist trap that is Ashington (rugby events in Newcastle having raised the airport  hotel rooms from £50 to £300 a night), we were pretty groggy by the time it came to navigating a hire car out of Faro Airport. Mrs FVM asked "Are you sure this is the right road?". "Yes", I replied "I recognise that mast", pointing to an amateur's Earth-Moon-Earth capable array which I had noted several times before.

So it was that type of "no radio" holiday: the sort that spots every antenna, hand portable or reference to radio.

As a holiday it worked well at every level, with 33C temperatures and clear skies for the whole time. Excellent food and even a little drink. Those plus points even got me onto a cliff top - well if you call a crumbling bank a cliff. It was nothing like the local cliffs at Burnmouth.
GM4FVM above Fal├ęsia Beach (that is what passes for relaxed looking).
The view might look OK from the top with Albufeira in the distance, but the cliff really was not much more than a mound. I dare say that they have dramatic cliffs in Portugal, but these were a pretty ordinary ones.

"Cliffs" on the Algarve near Villamoura
Quite a few domestic Portuguese TV antennas caught my eye. This one below did not a take a good photo, but you can see that it is quite a bit higher than the surrounding buildings (click image to enlarge if necessary).
TV reception antennas in Portugal
Clearly Portugal has a different approach to this than the UK. The system the UK adopted when we went progressively higher in frequency for TV broadcasts has been to install more and more subsidiary transmitters to fill in gaps in the coverage. While the US and other jurisdictions tended to adopt cable TV,  the UK preferred repeaters. The geographical facts of this country mean that fill-in stations are usually easy to site on hilltops. As a result, these days indoor antennas are pretty well standard in UK cities, and of course the increasing use of streaming TV services increases the trend towards the absence of antennas.

Also worth considering is that because the UK did not go for cable TV (who remembers Associated Rediffusion which started out in the 1920s as a cable radio network?) we did not have existing TV cables on which to build up a fibre internet network. Apart from what became the geographically limited Virgin Media network, we have had to rely on the copper twisted pair in the telephone system.

It wasn't always that outdoor antennas were unusual. I well remember the time when just about every house had a 50MHz beam on the chimney to receive 405-line VHF television signals. Even though Band 1 transmissions ended here 30 years ago, and they were largely ignored long before that, there are still a few of those old behemoths stuck on local chimneys.

One of my earliest childhood memories is the arrival of "UTV" in the late 1950s, which was the local Independent Television ("ITV") service. I was only a child at the time, but I remember the brand new TV which arrived to receive it, with the unusual device, a channel selector. Our previous set, which only had Band I, and thus only BBC reception, was transferred to my Grandmother's house and became here first TV. Later she was given a down converter which went into the antenna downlead and came with a switch to select Band 1 (BBC ~50MHz) or Band 3 (ITV ~ 174-230MHz). Needless to say receiving on two bands required multi-band antennas and the ironmongery on the rooftops got even heftier.

The earlier arrival of Band I TV saw the installation of many 50MHz yagis and crossed dipoles. These were particularly conspicuous where the signal came from a repeater station as these were (and still are) usually vertically polarised. By comparison my radio antennas are small beer, especially if they could be set alongside the TV masts and antennas of rural Ireland. There it was not uncommon to see 100 tall foot guyed masts topped with yagis, log periodics, dishes and all sorts of things, pointing to GI or GW in order to receive UK broadcasts. Where we lived in GI we had a local main transmitter, but we still had both Band I and Band III yagis on the chimney.

When we moved in 1962 we had to update the TV antennas on the chimney of our new house. My father was scathing about the radio antenna, which most houses had pre-War (our house was built in 1937). We found a neat Belling-Lee socket by the living room window frame, through which an "Inverted L" wire antenna rose to the chimney and across to a tall mast down the garden. My father took great glee in chopping down the mast with a hacksaw, now that modernity had arrived in the shape of our 405-line black and white TV. I later wished he had left it. The cable of the radio antenna, carefully fed through the window frame but now cut on either side of the frame, was still there 40 years later when the house was demolished.

The fact that houses had tall, long, wire receiving antennas and masts before TV arrived is often forgotten these days.

Later we got a multi-standard TV for the new 625 line BBC 2 standard, and I remember at some stage taking it apart to convert the 405 line BBC 1 and ITV reception to 625 line. This brought congratulations from my father who immediately noticed the improvement in sound quality (405 line TV had AM sound) and picture resolution. Some years later that TV did what so many of them did in those days - it caught fire helped by the hot valves, and set fire to the curtains behind it. Luckily we put the fire out.

Anyway, the point I am getting at is that here in the UK was have moved from a world where antennas were large, high and commonplace, to a place where such things are unusual. Nowadays our Town and Country Planners frown upon antennas (except domestic satellite dishes which are largely exempt from the Planning laws!).

In the UK planning is administered by local authorities (i.e. municipalities).There are 343 "Councils" in England, 44 in Wales, 32 in Scotland and 11 in Northern Ireland. Most of these have planning powers. If that wasn't enough, in general they consult lower tier institutions about planning issues, such as "Parish Councils" in England and "Community Councils" in Scotland ... and so forth.

It is hardly surprising given the complexity of the local government system that what constitutes a reasonable development, and what is a blot on the landscape, varies enormously. If you happen to live in a conservation area, like an ancient town centre, the planning authority is likely to regard whatever antenna you plan to put up as an insult to local aesthetics. Elsewhere, some councils would not regard some antennas as subject to planning at all. Many councils do not want to get involved with minor issues, preferring to get them resolved locally. At the other extreme some local councillors, eager to get re-elected, will take personal umbridge at any pimple on the roof line. I recall a case where a councillor assured the amateur that he would make it his personal goal in life to get the antennas removed, and so he did.

There is no common definition as to what is a "structure". Sure, everybody knows that a new house is a structure, but is a shed or a greenhouse? Is a pole for a clothes line different from a mast? Is an antenna a structure at all? Well, it depends on which council area you live in. It also depends a lot on whether your neighbours object to it. It is generally accepted that a wire antenna is not a structure for this purpose (there the agreement about antennas ends). Some councils are not concerned about modest antennas attached to houses, or those which are less that a certain height about the roof line. Very much "it depends".

Some councils are very keen to run a side-line in issuing "letters of comfort" to anyone who has something like an antenna which the council has decided (often because the antenna has been in place for four years or more) is not subject to the planning rules. They charge sums like £60 for these - I know I bought one at a previous house. What a nice earner for the council who did not even come to look at what it was they were granting me comfort for.

So there is no simple answer. I have heard of several UK amateurs who have had to process expensive and slow planning applications for 2m and 70cms antennas which are no more noticeable than a television antenna. On the other end of the scale, some have put up free-standing lattice towers with HF beams and had no trouble at all. The variation is caused by the fact that they live in different council areas or are covered by different planning authorities (and they have different neighbours).

The Radio Society of Great Britain runs a service to help amateurs deal with planning problems. I have not needed to use it (yet!) but it gets good reviews. National radio societies do have their uses, and this is a good one.

My Portuguese antenna-spotting trip is now over. I think it is clear that the planning rules in Portugal seem to allow these things, or that permission can be granted. Here, we used to have so many antennas that we stopped noticing them. Now we have so few that any amateur antenna at all seems to attract local objections.

If you look up "TV antenna" on Wikipedia you get an article and this photo of a multi-band set-up.
"Antenna" - by Yonatan Horan - Own work, CC BY 2.5,
Clearly in some places, maybe not just Portugal, multiband antennas are common place. However, in the UK they now seem to be frowned upon.

In the UK power and telephone cables are buried in all new urban construction, and this provision has applied for many decades now. It is now normal to see UK town skylines looking very uncluttered. Only old-established town centres have above ground cables (thankfully, given the radio noise they emit). People are beginning to view anything above ground as abnormal.

What the future holds, I dread to think.

I am back now, refreshed and still a bit fed up with radio. Perhaps some radio operation would help.




Thursday, 9 May 2019

Icom IC-9700 PTT switching - something I do not understand.

I have, of course, been watching developments on the IC9700 front for some time. It looks like and interesting radio for those of us who work on both 144MHz and 430MHz, and adds 1296MHz for good measure.

Maybe I have got this wrong, but it appears to me that the 9700 cannot switch different linear amplifiers on its different bands.

This is not such a hard thing to do. My IC7100 can do it. You can switch the two pins on the 13-pin socket between either working HF and VHF separately, or 2m/70cms separately. This is something I do. The IC-7100 has a "standard" 13 pin Icom output socket. However, the IC9700 seems only to have the other "standard" 7-pin socket. This has many things which I don't need, like RTTY switching, but it only has one PTT output pin.

Here is how the IC-7100 does it (one output is called HSEND, and the other VSEND) ...
IC-7100 manual showing clearly how to set the two separate PTT outputs.
As usual, click the images to enlarge if necessary.

You select what you want in the settings ...
IC-7100 manual showing how to select the automatic PTT band switching.

I do not own an IC-9700 and I have to rely on the "basic" version of the manual published by Icom UK. This does not show almost all of section 2 which would reveal the details. However that manual does show an explanation of the pin outs for the accessory plug ...
IC-9700 "basic" manual showing just one PTT output.

Now, as I say, I don't have an IC-9700 so I cannot verify if they are indeed being supplied with the 7 pin socket. However, elsewhere in the manual there is an explanation of how to set the single PTT output to work on specific bands
IC-9700 "basic" manual showing how to set the single PTT output.
This is, of course, consistent with the wiring details shown in the other part of the basic manual. It appears from this that you can set the single PTT output to on or off on any specific band, any combination of bands, or none.

It seems strange to me that a rig with three RF outputs only has one output for switching linear amplifiers. With the IC-7100, for instance, I can set it up with my 2m amplifier on one RF socket, and my 4m amp on the other socket, and it decides which amp to key. The same goes for 2m and 6m, and I have had it set that way too. You could also do this in the IC-7100 for 2m and 70cms, using a diplexer, but I have never tried that. I would have thought that this would have been a pretty obvious arrangement for the 9700 too.

I do wonder why the 9700, a radio with three RF outputs on the back, has only one PTT output, whereas the IC-7100 has two RF outputs and has full flexibility as to which PTT works with which. Why does the 9700 have the 7 pin plug when even the IC-7300, which has only one RF plug on the back, has the 13 pin plug. The IC-9700 seems to have taken a step backwards here.

From what I can see, the IC-9100 also had the 13-pin socket and the two PTT output, so if I was was replacing an IC-9100 with a IC-9700 I would be pretty miffed about this. It was a development of the 7100 system, allowing some limited choice between some of the bands. Shown below, from the 9100 manual, is the paragraph I would have wanted to see in the 9700s manual ...
The IC-9100 manual showing how it should be done.

OK, I have not seen a UK version 9700, nor even a full manual. Hopefully some 9700 owner can come on and tell me that the rig did, eventually, sell with the 13 pin plug and even the basic connectivity of the 7100 or 9100. If so, I can happily delete this post.

Is this a deal breaker for me? Probably in the sense that an IC-9700 would be a very good single band rig for me, but I could not use its multi-band capability. Sure I could rig up a switch to turn the PTT between the amplifiers, but I would only need to make one mistake with that to blow up my mast head pre-amps. I did not go to all the trouble of sequencing them to risk sending RF up to them with no PTT active.

I do not rule out getting an IC--9700, but it would be limited by this issue. I cannot see myself going into the menu to change the PTT settings every time I change bands, and the consequences of forgetting or getting it wrong are too expensive to contemplate. And anyway, isn't this what a multi-band radio is supposed to avoid? If the feature was worth putting in the 7100 and 9100, why leave it out of the 9700?

I have thought up a circuit which would RF sense the outputs and turn the PTT in line with that. This would mean that only the first transmission would go without the matching PTT - thereafter it would stay switched until I changed band again. But how often would I need to do that before the pre-amps died?

If you do not use amplifers and pre-amps this does not matter to you. Until you come to sell it of course, when such things make or break second hand sales.

It seems to me that it would have been sensible for Icom to have carried over the socket, the circuity and the software from the IC-9100 to the IC-9700 so that the very many VHF-ers who have multiple linear amplifiers could use them. After all, Icom had already figured out how to do it more than five years ago on the IC-7100.

But then again, are the production models supplied as the manual I have seen suggests? I hope not.



GM4FVM (EDIT - not just linears, but SHF transverter control is affect by this issue too)

Tuesday, 30 April 2019

"Streamlining" the antennas, and the Es season starts.

Simplification is not a word you might expect to apply to GM4FVM.

I have two excellent VHF antennas, a 5 element for 4m, and a 5 element for 6m. Both are PowAbeam designs, robust and very effective. They both have 3 metre booms, lots of gain, and work very well. Yet both have been taken down and are in my antenna-rich garage.

The cause of this action is that I have decided to make things a bit simpler. Less aluminium in the air, less strain on the rotators, one less linear amplifier and less yagi to annoy the neighbours. Simpler. An unusual concept round here, but that is what has happened.

Now shame on you who looked a my last post and did not mention that I had mounted the elements on the 4m/6m dual band beam in the wrong order. Tut tut. I am sure that the more observant noticed this but decided not to comment. Several of you commented by mail about the silent-key dilemma, and thank you for that. The silent key issue is a tricky one, and I am sure that you wanted to handle it delicately. So, you noticed that the elements were the wrong way round, but you kept quiet to spare my embarrassment.

I have now also put back up my 4m vertical, which fell over in a gale some time ago. Here are the two together, this time with the 4m and 6m driven elements on the yagi reversed. The vertical antenna on top of the yagi is a Diamond X-50 for 2m FM (well, actually used mostly for listening to Aberdeen Coastguard as there are no locals left on 2m FM).
5/8th 4m ringbase vertical and 4m/6m dual band beam at GM4FVM

I must offer something in defence of my stupidity. I took the old Vine dual band antenna out of the garage and gave it a spruce up. It must be ten years old, and last saw service temporarily as a 6m antenna in the past year or two. When I took it down I had carefully marked every element with labels including for this pair "4m BACK, 6m FRONT", not just on the mounting for the elements, but on the boom too. So when I put it together I made sure it was right. I did also notice that the coax connection to the driven element was getting a bit ragged.

As soon as it went up I had a high SWR. A quick examination revealed that water had got in and corroded the coax. So I took the driven elements off (they are mounted together) and took them into the house for surgery. This involved cutting back the coax, shortening the choke balun, soldering new ring tags and making good with lots of self-amalgamating tape. Then I put the two driven elements back, and, as I now know, I PUT THEM BACK IN REVERSE ORDER.

This was silly, but I was in a hurry to test the antenna. I still had the 5 element PowAbeam up so I was going to run a long series of tests to compare the two. Even with the elements in the wrong place, the results were plain - a 4 element with a 2 metre long boom is not as good as a 5 element on a 3 metre long boom. No news there then. But the tests showed that the reduction is only around the 1 dB expected and really quite manageable.

This dual band beam was in use at GM4FVM for some years before I decided that separate beams for each band were better. That is still true, but it comes with greater complication, two sets of coax, two rigs ... and just for now I would prefer something with less metalwork up in the air. So one old dual band beam has been tidied up and pressed into service in place of two larger ones. If it doesn't work I can always change back.

The trial I did between the two antennas involved pointing both at the GB3CFG 70MHz beacon near Carrickfergus in Northern Ireland (about 250km away) and monitoring the PI4 signal decodes simultaneously for 3 hours. The outcome showed all I needed it to show - the dual band antenna might be marginally worse than the single band one but not more than 1dB or so overall. I have decided that I can cope with 1dB on 4m (for now anyway).

As for putting the vertical back up, well it is now my second antenna. It works fine on 4m, I can receive on 6m, and with an IC-7100 attached (the one that covers for 70cms) I can switch it about to whatever band I want to hear while using the dual band beam for something else. Job done (well, once I put the elements on the right way).

What a job fixing the elements proved to be. I knew something was wrong, but I could not figure out what. I went out and straightened every element, measured the differences between the elements, tried to fathom why the 4m SWR was high, checked the coax, switched around all the leads in the shack .... I am sure it was only a matter of time before one of you sent me an email to explain that they were the wrong way round in the photo on the last blog ....

It dawned on me while watching a repeat of the 2017 Masterchef Australia on the Home channel. Yes, I watched every one of the 63 daily episodes in 2017, and I am now doing the same as they re-appear this year. And suddenly, while watching Kirsten Tibballs explain her chocolate mystery box challenge, it dawned on me - the elements must be back to front. And so it proved to be.

Spoiler alert. The mystery box was made of chocolate, so they could use the box in the cooking as well as the contents.

The moral? Stop thinking about your problem and you will do your best thinking. Distraction is generally my best way of solving problems.

So it was out at 08:00 next morning and, yes, they were the wrong way round. The SWR was now excellent. And then, as if by magic, the Es season started.
VHF Es contacts at GM4FVM on 23 to 25 April 2019
Well, the GM contact wasn't Es, but the rest were. There were two stations in Croatia which were on 4m, the rest on 6m. I had the usual rush of blood to the head, working a lot of stations I might not otherwise have bothered with just because I could hear them after months of silence. This enthusiasm will wear off me, and wear off them. By August they won't bother with GMs.

Since then, we have had three days with no Es. Such is life. I don't care, now that it has started it will be back.

Frankly, most amateurs using both 4m and 6m use a dual band beam, or a log periodic, or something similar. Separate beams might be better, but the final dB comes at a cost. It got harder to argue for separate beams when I was having such success with a 2m/70cms dual band yagi.

The dual band 4m/6m yagi antenna now works fine. I can listen to the other band with the vertical too.

First indications suggest that my simplification worked once I realised how to put the antenna together the right way. After fixing the TE Systems 6m linear I don't need it as the Gemini 4 covers both bands. The changes also clear the 4m single band beam away from the other mast to allow me to tinker with my 2m and 70cms antenna - but more on that later if I ever get round to it.

Simpler? Oh yes, but GM4FVM-style simpler which means still a bit mixed up.




Wednesday, 24 April 2019

The equipment sale of a silent key amateur caused me doubts

Four or five months ago a local amateur became silent key. I shall not mention his callsign and I shall call him "Roland" here. I do not want to cause any distress.

Roland lived about 20 miles from me in the Tweed Valley. I encountered him 5 or 6 years ago when he came over the GM4FVM a couple of times to see my set-up. He wanted to create something similar as his interest was in VHF, and there are not many others round here doing that. So he phoned me a few times and then came and looked, and later built something similar.

When Roland passed away a fairly common situation arose. Basically his equipment was to be disposed of very quickly by people who did not really know what it was. At this stage I was contacted by his brother in law, also an amateur, to see if I could help. The initial questions surrounded Roland's IC-7100, the purpose of which was unknown to anyone. I went over and explained to his brother in law how it worked.

The next thing which emerged was that everything was to go, and as soon as possible. Roland's 10m Tennamast, 2m, 4m and 6m antennas, rotator and all associated metalwork was taken down and left on his front drive. I was asked about it and I quickly offered the Tennamast to another amateur in the area who I knew was interested in one. However, he only needed a 7m Tenna, so there were no takers. The antennas and the Tennamast were quickly scrapped.

This was a bit of a wake-up call. Coax and rotator cables had been chopped up to get them out of position. The cables for the IC-7100 could not be found, neither could the associated CD, nor various similar items. Large quantities of magazines and paperwork went to the local dump, so different items were being separated from their manuals. I was told that the rotator was headed for the dump.

Faced with this, I was unsure how to act. I did not want to see valuable items being dumped. Roland's widow deserved to get some value for them. The Tennamast had already been assigned for scrap. So I stepped in and bought the rotator, the IC-7100 and an old low-spec oscilloscope. I really had no need for any of these items, but I did not want to see them dumped. I then had to scrabble together a large sum in cash and hand it over, something we don't do much in these days of plastic money.

I had to deal with the issue of how much to pay for some things I didn't really want and I was not even very sure about their history. I had never heard Roland on the air - if he ever transmitted I never heard him, nor had I met anyone who had worked him. Had I not heard him because nothing worked? The amount had to be high enough to make Roland's widow better off than scrapping them or other disposal. I did not want to hear later that these items were sold off too cheaply. The scrap value for the Tenna mast might not have been zero but was certainly very low compared to its true value as a mast. The other items were headed for the dump.

I had to make it very clear that if these items were carefully marketed on eBay they might fetch more, and if they were offered for a straight sale to a dealer they might fetch less than that but more than I might pay. Either way was an option for the estate. In the end, as I say, I bought three items. Some other things found good homes, in particular a rather nice ATU. A couple of small high value items were rescued and remain to be sold, including a DMR handheld and an MFJ antenna analyser, but everything else was thrown away.

I apologise if I have got some details of this wrong, but it all happened very quickly, and a lot of it occurred outside my knowledge. I was not directly involved in most of it. However, it is clear to me that there was no plan as to what to do, and the need to do it quickly probably resulted in high value items being scrapped or thrown away.

Still, some good came of it.
Roland's Yaesu G-450 rotator had to be hastily pressed into service yesterday when the azimuth sensing potentiometer in my G-450 failed. OK, it had sat in my garage for 4 months while I wondered what to do with it, but it came good in the end.

You may notice that my 6 metre antenna has changed again, it is now my old 4m/6m Vine dual band antenna resurrected. Why do I need 2 antennas on 4m? More on that later.

My original 450's pot should be easy to fix but it was very handy having a spare rotator to change over. The job only took just over an hour to do.

If I had any idea what to do with Roland's rotator it was to use the control box as the basis for a plan to use my EA4TX controller to run the G-450. I was working on that when the rotator pot failed. The controller plan wasn't going well by the way, as the voltage on the G-450 azimuth sensing line was very low and too low for the EA4TX unit to reliably measure. Never mind that for now.

And Roland's old IC-7100 is also in use. I did not need another radio. I still don't. The arrival of the IC-7100 might have seen it sit idle like the rotator. As it turns out, the IC-7100 is just what I needed for 70cms, and the rig sitting idle is my IC-7300. Who would ever have thought I would end up with a radio as good as an IC-7300 sitting here doing nothing?  It just proves that I did not need another rig.

The moral of this story? Well, Yaesu rotators break down --- NO --- the moral is that we do need to think about what would happen if we end up going silent key. It is the necessary result of being alive that at some stage life will leave us. Is it fair to abandon our nearest and dearest to sort out what we leave behind? Is a mountain of old gear easily sold off by grieving relatives? Can we provide for this in some better way?

I read an article on this subject a year or so back in Somebody who had acted for two widows in selling off SK gear had written to say that we should be better prepared. He acted in good faith, and one widow left him to it, the other demanded cash receipts and detailed accounts and justifications for each sale. In an slightly older local case, a couple of amateurs who acted in good faith were later accused of feathering their own nests. I certainly thought they paid fair prices for piles of old and uncertain gear, but the widow later accosted one of them in the street and accused him of under paying. It left everyone feeling uncomfortable.

So I ask this general question - if you were to die tomorrow, would anyone know what to do with your gear? Would they even know what it is? Shouldn't you write down what it is and what to do with it? Should it go on eBay? Should it go to a dealer? Is any one person to be trusted to sell it off? And what if the trusted seller want to buy some themselves? What price is fair then?

I fell sad about the way that Roland left this world. His carefully assembled radio shack was never used for what it was designed for. What did he do in his shack for all those years? His expensive cables were cut up. Some of his gear could not even be identified by the people sent to remove it.

Perhaps it was inevitable that a lifetime's collection of Rad Coms went straight to the paper recycling section of the local dump. But some things that others could have re-used were scrapped. If more had been known, and more time spent on it, I believe that more money could have been recovered. But perhaps more importantly, some gear could still be being used.

I hope that Roland takes a break from operating in that great shack in the air sometimes to look down and see his rotator turning my beam.




Friday, 12 April 2019

"Almost Sporadic E" and 6 metre band readiness

At the start of April we find ourselves back in the "Almost Sporadic E Season".

For the past ten days I have been decoding one-way FT8 signals on 50MHz which look like Sporadic E, and so have others. Sometimes I have called CQ and been heard all over the place ...
Stations reporting hearing GM4FVM on 50MHz, 7 April 2019, on PSK Reporter
All of this has produced just one QSO for me - SP4MPB on 4 April. The rest of the time I just see parts of signals being received. Even more frustratingly, I see myself being reported as heard be other stations, but I hear no replies. Collections of dots and lines which are almost enough to decode but not quite there, then maybe at a different time several decodes. Although I can receive them, none of the stations answer when I call. Lots of activity, even quite a few decodes at time, but only once a QSO.

Almost Sporadic E.

There could be lots of explanations for this, but I think it is all the more noticeable thanks to WSJT-X and that darned mode FT8. I have speculated before about the ability of the "weak signal" modes to receive signals which are otherwise inaudible, and this may exploit the effect of partial reflection in the ionosphere.

"Above MUF propagation" is a fairly silly expression, but what it means is "above normal MUF propagation", in other words by using very sensitive protocols like FT8 we can decode signals we never noticed before.
Plenty of 6m activity on PSK Reporter, 9 April 2019, no QSOs though.

Partial reflection occurs when there is refraction, but usually we do not notice it because the refraction produces a much stronger signal which swamps the partial reflection. It may cause phase differential QSB, which many of us note on radio signals without giving much thought to the causes. However, just now the E layer is only strong enough to produce some refraction but not enough to deflect the signal back to Earth, so the weaker reflected one is heard.

Partial reflection is really only capable of being understood as a quantum effect. I do not think that I am alone when I say that at school I was taught the wave theory of radio propagation in my physics classes. It is very comforting to think of radio progressing as a wave, especially as many observed radio effects can be explained by wave theory. But wave theory does not explain partial reflection. Like many more complex aspects of elecro-magnetic theory, we need to consider quantum effects to understand it.

When considered in quantum terms, radio energy travels in straight lines carried by photons, and these are only deflected by:-
a) gravity (but the Earth's gravity is too weak to have any significant effect)
b) collision (producing what we know in radio as scattering)
c) refraction (the main way signals are deflected back to Earth)
d) reflection (quite rare at common radio frequencies).
It is in the process of refraction that partial reflection occurs, and it is often dismissed as a byproduct as it is very weak.

You could add to that list e) absorption. Radio signals encountering a very dense object will be effectively absorbed. The object gets hotter, and the photons involved cease to exist. Not really deflection, but worth mentioning. Although there is some absorption (and scattering) in the atmosphere, the radio signals we notice getting weaker do so mostly due to the Inverse Square Law

However, you will note that neither electric nor magnetic fields deflect photons, so neither the ionisation itself, nor the Earth's magnetic field, will deflect a photon in the ionosphere. What we hear back on Earth is almost returned to us due to refraction (plus a tiny element of reflection).

I had written 10 long paragraphs on the subject of the analysis of radio propagation from a quantum perspective. It is all so complex it hardly seems worth it. I have just deleted them. Instead I will show my home drawn diagram from the earlier posting again, and it applies equally to the E-layer as it does to the F-layer:-

The partial reflections, shown by the white lines, would normally be swamped by the main signal, but just now the ionisation is not quite strong enough to refract the main signal back to Earth. So we have some weak reflections, and we would never notice them were it not for using FT8 and other very sensitive modes.

As partial reflection is a quantum effect it happens in the world of probabilities. We can see through glass yet from the correct angle it can reflect light too. Up to 4% of a light beam falling on a single layer of glass is probably reflected by this process. "Up to" and "probably" being key here. The effect we see with glass is faint and ghostly. You have probably seen reflections from glass, when you expect to see through a shop window but also see a faint impression of yourself as a reflection.

In the dire 1960s UK comedy TV series "Harry Worth", Harry used to open the show with a recording of himself reflected in a shop window .... no Jim, don't go back there again. Harry Worth's TV show should be forgotten but, yes, it did feature partial reflection in the titles. Yes, Harry was a bit of an amateur scientist. Anyway, partial reflection is a faint, shadowy event, and that seems to explain what I am hearing.
Harry Worth (the things we used to find funny) Photo Wikipedia (Fair Use).
Sure you can also explain these strange signals in other ways. For example, maybe the ionisation is rapidly variable and just reaching levels able to support refraction. I do not think so, as these signals are very weak (Es is very strong), and there is a one-way element. I can copy one or two or even three signals from station, but they do not hear me at all. At other times different stations hear me and I do not hear them.

If you look at my diagram and imagine another signal coming the other way you can see that the angles do not match up - you could not reverse the angles symmetrically as the path of the signal passing the other way would need to be pass through a different patch of ionisation - and Es clouds are notoriously localised.

Whilst it is possible a second patch of ionisation would occur, or the first one is wide enough, it is unlikely to happen until there is much more ionisation - not until into the Es season proper. If this sounds odd it is due to the asymmetry of the path - the partially refracted signal is not straight, whereas the reflected one is more likely to arrive at a different angle as it passes through different paths of ionised space. While the path my exist, the signal will be a different strength. This effect becomes less as more ionisation occurs.

Certainly there is marked one way propagation in the present period. Soon we will have more ionisation, stronger refraction, and we can forget these odd lumpy traces on our waterfalls.
In order to be ready, and as predicted in my last posting, I have readied my 6m linear amplifier. I have taken the TE Systems 0552G out of its box, cleaned all the corroded cables, tuned it up, and Hey Presto!, it works. I suspect that the trouble was simply power starvation after the 50 amp drawn through the PSU output terminals melted everything that would melt and scorched and blackened everything else.

I have imposed a current limit of 40 amps, but I can still get 200W output for that so it is no hardship.

As I suggested in the last posting, the three element 50MHz antenna seems to be fine for now. Perhaps by late May I will feel the need for something bigger.

Also mentioned last time, I am investigating more power on 70cms. Not a lot more, but maybe up to 3dB more would help the Earth Moon Earth strike rate a lot.
At last, thing are beginning to look better for the new season. Well, I did work SP4MPB, so technically the Es season has started and the Lyrids meteor shower should be going soon.


P.S. I have to post this now, as I have spent so much time drawing diagrams of one-way paths, small patches of ionisation, asymmetry ... grrr ... I am going MAD. Quantum theory, who needs it?

Wednesday, 3 April 2019

"Much Ado About Nothing" (or "Progress So Far")

"Ain't nothing going on but the rent".

So sang Gwen Guthrie, some time ago, in her Top 5 hit of the same name. Over 30 years ago, actually.

A fair sentiment, but I do not like the sentence construction. "There is nothing going on except for incurring the expense of the rent" would have been much more correct, grammatically speaking. You don't get no grammar like that in this blog, no you don't, not never, ever.

Even that there Paul Simon does double negatives "I don't know nothing about no Mexico". Surely that word "no" is tautological, or at the very least, redundant.

I think that my hopes of establishing a successful song writing career are being dashed.

Thanks to Jacob Rees-Mogg for that contribution to the blog in relation to proper English as she is spoke.
Jacob Rees-Mogg (or is it Gwen Guthrie?) Photo

I get confused.

Early April is often a bleak time for VHF radio enthusiasts. Ain't nothing going on but the cosmic background noise. Ah yes, Gwen Guthrie was right. Or maybe she ain't wrong.

You can of course go and spend some money instead. Ms Guthrie's opus also contains the line "no romance without finance", which sounds a bit like a radio dealer "no radio without finance". Luckily, it is not true, or at least not true if you avoid the radio dealer (Gwen, sadly, is SK now).

To keep himself occupied, a local amateur has bought a DMR digital handheld. The problem arises that we only have a handful of local stations left and none of them has any sort of digital voice radio. He has nobody to work without resorting to a repeater or the internet. He said "I have discovered that it's not real radio" - THAT WAS WHAT HE SAID, DO NOT BLAME ME.

Here at GM4FVM castle we have not spent any money, apart from £6.25 at the ship chandlers at Eyemouth for some hooks and eyes to build a 15m dipole. The usual seasonal preparations are underway. On 6m, where my antenna is always exposed to the wind, I have taken down the Winter Only HB9CV. This is pretty slippery when it comes to wind profile, so it occupied the space during the worst of the weather. In its place went the Sirio SY50-3 3 element yagi.

I was in a bit of a bind as to whether to put back the 5 element PowABeam rather than the Sirio. I have to be aware of the visible nature of our hobby. I do not want to put up anything larger than I need, and nor do I want to strain the rather limited Yaesu 450 rotator that it all sits upon. So I opted for the smaller 6m beam and took the surprising step of upgrading the Diamond x-30 vertical above it with an x-50. Wow! Another 1.5dB gain for the vertically polarised 2m stuff, and a similar reduction for 50MHz horizontal radiation.

There is no real answer to all this. Sure, putting up the x-50 brings in Humber Coastguard much better, which shows how quiet 2m FM has become. I now get far more to hear on the marine channels than I ever do on 144MHz FM. At the same time, 6m may not be my only priority for the incoming season.
As usual, during the April lull I have been reviewing progress during the year before and trying to see if there are any lessons to be learned.

Last year, mostly using the 5 element on 6m was not bad at all
6m stations worked at GM4FVM during the year to 1 April 2019
During that year, the all-time number of squares I had worked on 6m went up from 294 to 346, and DXCCs from 55 to 71. In fact I managed 66 DXCC in the last year alone. Despite all this I am sticking to the smaller 3 element yagi for now. I am doubtful that I can do much better with 5 elements. Sure, I would like to work South East Asia when that path opens, and I bet I will try. To do that I will need to fix the 6m linear amplifier, which is the one big thing on the "to do" list. But I doubt that 3 dB from the amplifier and 1dB from the larger antenna will really make too much difference. Fundamentally, I need a better opening than I have seen in recent years.

6m has been great and I have no wish to scale back on it, but neither am I going to risk stripping the gears in the rotator. So the 5 element will remain in the garage, for now. I will stick to 3 elements. I did change the TS-590 for an IC-7300, which allows me to watch what is going on while I am doing other things. It is surprising how useful it is to be able to see stations far outside the audio passband, especially on rather erratic VHF bands.

The four metre band (70MHz) has been good too.
4m stations worked at GM4FVM during the year to 1 April 2019
It was a pleasure to add a mainland African station to my list of places worked (though I had worked the Canary Islands before). Nothing trans-Atlantic on 4m yet ... with Greenland managing to escape me last year. Nor yet Asia, with Israel a tantalising prospect as well as several of the Central Asian states. Nothing much has changed on my 4m station, and I am still using the 5 element PowABeam for that band.

One thing I have considered is a 4m masthead pre-amplifier. It certainly helped at 144MHz, but the benefit at 70MHz would be a lot less. So, for now, I am leaving that question open.

144MHz has also been good this year...
2m stations worked at GM4FVM during the year to 1 April 2019
I think in that map I can still see poorer results over a range of beam headings to the South-South East of me. I do not seem to get out well into Belgium, Eastern France or Switzerland. Given how well I am getting out in other directions I think I can forget about that. OK, the hills near me have some effect, but nothing like as much as I had once thought. There is reason there for anyone in an obstructed location to ignore the rules and try VHF anyway.

My 2m tropo contact to the Canary Islands catches the eye on that chart, though the QSOs into Spain were just as notable from my point of view. Only a small number of contacts were made via EME, most via tropo, with some meteor scatter and a little Sporadic E thrown in.

During the year my trusty 7 element DK7ZB antenna by Wimo was replaced by a very similar-looking one from Antennas+Amplifiers which also has a 70cm antenna on the same boom. At the start of the year I added a masthead pre-amplifier and the LinearAmp Gemini 2 to the 144MHz line up. I have no further changes planned for now.

So last year increased my 2m DXCC total from 24 to 30, and the squares from 92 to 146. Basically the present 2m set-up seems to be working and I can see no reason for changing it.

The 70cms station only dates from August 2018, and I might as well ignore anything before that (I worked nothing outside about a 20km radius in previous years).
70cms stations worked at GM4FVM during the year to 1 April 2019
Erm, my contact with NC1I on EME seems to skew everything a bit. I also worked HB and DL on EME, but the rest is tropo. 12 DXCC and 32 squares is pretty good by the standard of my expectations (which were for very little on 70cms). I have been proved totally wrong there. Even just using my 12 element multi-band antenna, an IC-7100, cheap masthead pre-amp and second hand 95w linear, I have far exceeded what I expected to do in 8 months.

The credit for all this goes to the 70cms band rather than me. In other words thanks to Earth Science and God Bless Mother Nature ("She's a single woman too" - another obscure musical reference, this time to a different song of the same era). My paltry effort on 70cms produced very good results and the only reason why I am surprised is that I had some earlier idea that 70cms was not going to be very good from here.

As for making any changes based on what I have learned from 70cms, well, I do wonder if a bit more power than 95 Watts might be something worth having especially for moonbounce. Like the VHF bands, I reckon that 50 Watts is generally enough on 70cms (not quite enough for EME!!!). However, that is only if you are beaming at each other; you need the extra power to attract the other station's attention. This is even harder on 70cms, where the beamwidths are smaller and the chances of anyone beaming at you are therefore lower.

For now though no changes are planned to the 70cm station.
The danger of the long VHF lull roughly between the second week in January and mid-April (which is the end of the Quadrantids to the start of the Lyrids, or if you prefer, the end of Winter Es and the start of the Summer Es season - ish) is that you buy something like a DMR handheld to fill the gap. In my case my idle hands find work in devilish maps and statistics to show where I have been going wrong over the past year.

I have been going wrong by thinking that the hills near me made 2m DX very difficult, or by thinking that 70cms would not do well from here, or by imagining that I would never work South America on 6m, or mainland Africa on 4m. All of those limiting ideas have been proved wrong over the past year. It is so easy to limit yourself by lazy thinking, or at least it is for me.

It isn't about me. It is about the science of radio. Take that amazing moment when I called a US station via moonbounce on 70cms and he actually replied. I doubted myself so much that I did it again the next day to prove it was possible. Or hearing that Canarian station on 2m and being totally bowled over when he came back to my call. If he hadn't worked 2 other GMs at the same time I would have doubted it ever happened. Or Mexico ... Mexico ... on 6m, actually further away than the Brazilian station I also worked that week. South Sahara on 4m calling CQ and working dozens of Europeans. There were Libyan and Algerian stations on 6m with pile-ups. I was scrabbling to work Russia on 2m meteor scatter ...

There is a thrill to all this and it has not got much to do with output power, antenna height or coax loss. Whatever your goals it is amazing when nature opens the door for it to happen.

Wonderment, I suppose, is my reaction. Certainly, I can examine my station and think about what I could have done better, but really I feel privileged just to have been there.

Who said VHF is limited by "line of sight"?

"God bless mother nature, she's a single woman too
She took off to heaven and she did what she had to do
She taught every angel, she rearranged the sky..."

Erm, that might be true but I think we had better ignore the rest of that song for our purpose.
Here's to another VHF season. We will miss those who have left us, and welcome some new stations, and, hopefully, there is more wonderment to be had over the next 12 months.

Just a couple of weeks more to wait ...



Friday, 15 March 2019

David Anderson, GM4JJJ, SK

I was saddened to hear last night from David's wife Pat that he had passed away yesterday.

GM4FVM with David GM4JJJ in August 2018 - photo taken by Pat
I first worked David on 4 April 1977 when he was GM8HEY and I was GI4FVM. I guess that neither of us expected to still be in contact over 40 years later. Working David then was DX on 2m for me, later of course we ended up about 100km apart and spoke regularly.

David's interests over the years extended to VHF generally and Earth-Moon-Earth communication in particular. He wrote the "Moonsked" software still in use by many enthusiasts to this day. He worked for many years in the electronics industry and his thorough knowledge of practical circuits was offered freely to many amateurs who were having problems.

Our background interests were different, mine more into the physics of radio, David's more into the electronics, but that turned out to be a perfect mix. We found that we were both interested in the particular interests of the other. We shared lots of information, and neither of us suffered the same fools gladly (especially certain equipment suppliers). David also added useful information to this blog.

It was so helpful to have him to bounce ideas off and I miss him already. .

Despite having to deal with a long illness, David remained positive. He continued to offer me advice right up to the point where he found it better to rest than operate on the radio. I will always be grateful for his friendship.

To Pat and to David's family I send my condolences. I have lost a mentor as well as a friend.

73's David


Saturday, 9 March 2019

More tropo, masthead pre-amps and sequencing.

I don't have to look far to find a masthead pre-amp at GM4FVM. The (now redundant) terrestrial TV antenna here has one.

Terrestrial television antenna at GM4FVM, with bandpassfilter and masthead pre-amp
I'll deal first with recent events before moving on to pre-amps etc.

The past month brought record February temperatures to Scotland, reaching over 18 degrees when at the same time last year we were cut off for five days by deep snow and had -11 degrees.

The cause for all this was a high pressure which poked its nose out from Continental Europe and settled down over the North Sea for a while. This is the opposite direction to the normal flow and resulted in the High blocking the normal passage of westerly winds from the Atlantic (or northerlies from the Pole).

This High did bring some tropo conditions, but it wasn't a great event. What has caught the attention is that such wide extreme of temperatures, such as the variation from last year, is exactly the progress we would expect to see if current climate change predictions are indeed valid.

Of course I am worried about the climate, but let us look at the radio for now, and then move on to the spellbinding  subject of mast head pre-amplifiers.

Things kicked off on 2 metres on 22 February when I worked DL3TW at 13:57. It was slow to build up, but I worked DL6BF to round it off on 2 March. Even for a 28 day month it is unusual for an opening to last here from 22 of one month into the second day of the next month. To be fair, there was a tailing off followed by a brief ridge of high pressure at the start of March, but it still lasted a long time.
Pleasing as that was, 70cms was better in my view ...
Despite all the 2 metres business, 70cms produced several new squares, including JO23 for PE1PIX (my first Netherlands station on 70cms), IO65 for GI0OTC and JO53 for DK0HAT. Many of the contacts started out as 2m QSOs during which I was asked to move to 70cms, and once again I was asked several times to move to 23cms which I cannot do (yet). Very good.

I have now reached 12 DXCC and 32 squares on 70cms, and they all feel like a lot greater individual  achievements than 30 DXCC and 146 squares on 2m.

The High has gone, the storms have returned, and all that is left for me at the moment is 4m meteor scatter. Moonbounce has produced few results recently, though I have heard Japan on 2m and China on 70cms.

Moving on ...

I said last time that I had thrown together a temporary sequencing jig to use while my Gemini 2 linear amplifier was out of operation. It is back now, but I had promised (threatened?) to write something about sequencing.

Before all the complex stuff I just want to say this. Adding a masthead pre-amplifer on 2m and 70cms absolutely transformed signals received at GM4FVM. Sure it is a fiddle, unless you buy a linear with the sequencing circuitry built in, in which case you still have to build or buy the pre-amp, but the results are excellent.

Where you locate a pre-amp becomes very important when dealing with Earth-Moon-Earth (EME) communication, but the same principles apply in all cases, and especially when it comes to using linear amplifiers. If you cannot hear stations you cannot work them.

In EME stations have to overcome very high levels of path losses, around 250dB. This means that the receive sensitivity of the station needs to be very high. Standard transceivers are not good enough for this, so a pre-amplifier is required. However, it is much more effective to amplify the received signal at the antenna before it passes down the coax cable and into the receiver (a so-called "masthead pre-amplifier"). The best signal-to-noise performance is achieved by locating the pre-amplifier before the signal suffers losses in the coax.

Another case is when you add a linear amplifier to an existing transceiver. By raising your transmitted signal by, say, 3dB, you may well feel that you need to raise the receive performance by a similar amount. This is because the stations who can now hear you may only be running the basic transceiver power you were running previously, and you won't hear them. This is why many common VHF linear amplifiers, e.g. RM Italy and Microset, have pre-amps built in. These may or may not be an advantage to your system, but once again a better place to do pre-amplification is closer to the antenna. Most high-end VHF linears do not have built-in pre-amps for the simple reason the makers expect high-end stations to have the pre-amp near the antenna on the mast head.

In an effort to receive out-of-area television, the terrestrial system at GM4FVM has a masthead pre-amp. Our local TV installer fits them as standard. On receive-only systems this is pretty simple to achieve. To save running a separate DC supply for the pre-amp most systems use a set-up which puts a DC bias voltage on the coax which is peeled off at the masthead and used to power the amplifier. This is done using a "Bias-Tee".

Simple masthead pre-amp arrangement for television reception
Put simply, it looked silly that a routine television installation would have a masthead pre-amp as standard when GM4FVM's VHF/UHF set-up did not have one. So I tried them out, and was really impressed by how well they worked.

It gets harder to apply such a simple set-up to a transmit/receive system like in a radio amateur's station. The pre-amp would be destroyed if driven by RF power during a transmission. Thus amateur pre-amps often have an RF-sensing "VOX", which will bypass the sensitive circuitry using a relay as soon as it senses RF power coming up the coax. The drawback of this system is that by the time the RF is sensed it has already arrived, so the damage may have been done. Also, the relays will take time to operate, increasing the risk of damage before the bypass is in operation.

The simplest way round this is to exploit the circuitry used in almost all pre-amps made for amateur transmitting use. By convention, when the DC power to the pre-amp is cut off, the relay is de-energised and defaults to the by-pass route. This allows just a simple on-off supply to the pre-amp. "Power on" activates both the receive circuitry and the relay, "power off" effectively turns it to transmit by turning everything off and so the de-energised relay switches everything out of the RF path. Note this this is the reverse of the convention for linear amplifiers, where the relays are energised on transmit.

Thus at a basic level all you need to do is to turn the pre-amp supply off at the same time as the push-to-talk line from the transceiver is grounded and you should be safe. However, you cannot use the PTT line as it works in the opposite sense, and using a relay to switch it makes it too slow to avoid damage on the pre-amp.

It can get even more complex than that, at least if you want more certainty at higher powers. You know that if something goes wrong with the switching circuit and the pre-amp remains live for any reason, the VOX should operate. However, most pre-amps set a very low limit for the power the pre-amp can handle when switched by VOX. This is because higher power risks building up before the VOX relay has activated.

To be safe, if the pre-amp should accidentally remain energised, it is best to take some steps to prevent full power reaching the pre-amp before the VOX relays have fully switched to by-pass. VOX might protect the circuitry at lower power levels, but it cannot guarantee to do this at high power. You can only really do this by not activating the linear amplifier until after a time lapse. OK, if some power does come through from the radio during that time it will reach the pre-amp at lower power and thus be safe for the VOX to cope with. Once the VOX has switched the relay for lower power then full power should be safe.

This should give you two elements in your system - one turns the power off to the pre-amp straight away, and the second delays any high-power reaching the pre-amp to begin with to allow time for the relays to work. In fact, either should work if the other does not. You might not think you need both, but you do. Or, at least, you will find that out for sure if you rely on either alone. Pre-amps are expensive, and you have to buy two if you blow the first one up.
2m and 70cms pre-amps on the mast at GM4FVM (I must shorten the 70cms cable)
My masthead pre-amp used on 2m has a rating for SSB of 350W on VOX (I can use 300W), but it can handle 750W when sequenced. I am not willing to risk 300W into it on VOX, especially as it it is rated at only 200W for FM, and my JT65 has a fairly high duty cycle. OK, so JT65 is not quite as demanding as FM, but moonbounce calls can be very long (as can meteor scatter ones). So this is where sequencing comes in for me.

A sequencer does everything in a certain order with a time gap in between to give relays time to act.  It does this at the start of a transmission, and restores everything in reverse order at the end. If you have added a pre-amp to balance a linear amplifier then it makes sense to control the linear too. At its simplest level you take the PTT line from the transceiver, which would usually go into the linear amplifier. You take this line instead to the sequencer. The sequencer then takes actions in sequence at the start of a transmission:-

Step 1 - cut off the DC supply to the pre-amp
Pause to allow the relay in the pre-amp to act
Step 2 - activate the PTT to the linear amplifier

This way you delay the possibility of full power from the linear reaching the pre-amp before it has had time to act. In the same process you have also changed the sense of the PTT line to cut off the pre-amp power as the first step to be taken and the last thing to be restored, protecting your expensive components.
2 step sequencing for an amateur station using a transceiver, linear and pre-amp

This is the system in use at GM4FVM. For sure I could add more layers of complexity, but so far it is working well. The only other step I have taken it to slightly increase the built-in sequencing time in WSJT-X ("TX delay") to 0.3 seconds.

You can, however, take sequencing to several further stages depending on your station.

How quickly you radio activates its PTT line in relation to sending out RF will vary - sometimes they might share the same relay, but generally the PTT will be quicker, which is a form of sequencing in its own way. I am content with this, but otherwise you can work the sequencer with a foot switch and let the sequencer operate the radio PTT after it has switched the pre-amp off and the linear to transmit.

Even more complexity can arise with transverters. You could use the sequencer to separate the transmit actions of the transverter from the transceiver, once again to protect the the transverter receive circuitry from accidentally receiving power from the transceiver.

Most designs for home construction, and commercial sequencers, allow you to program various permutations up to about 4, so that you can tailor their actions to your individual needs.
The 4 step Down East Microwave sequencer with 50pence piece for scale

Recognising that most amateurs will want to add a masthead pre-amp to balance the extra transmit power which comes with a linear amplifier, most makers of high power linears will include a sequencer and circuitry to control a masthead pre-amp with it. Certainly my Linear Amp Gemini 2 provides this, and I believe the OM  Power and Beko amplifiers also include it. The Gemini includes a plug which, which correctly wired, applies the DC bias voltage directly to the coax without the need for an outboard Bias-Tee.

If you do not add a linear, or it does not include a sequencer as standard, you will have to incorporate a Bias-Tee to add the DC voltage to supply the pre-amp.
SSB Electronic Bias-Tee
Some radio manufacturers of VHF equipment include bias circuitry in their radios. The IC-910 had such a feature. I imagine that the forthcoming IC-9700 will also have this built-in. This would be very useful if the radio was to be used barefoot, with 100W on 2m and 75W on 70cms being fairly useful power levels.

The results at GM4FVM - spectacular. As you might expect with losses in the coax increasing with frequency, higher frequencies show most potential for improvement. I was impressed by improved signals on 2m, but at 70cms the results were dramatic. For example, the 70cm beacon GB3NGI at IO65vb is 272km from me. On 70cms during flat conditions I can barely hear it. With the pre-amp in circuit it rises to a 569 signal. On moonbounce, signals vanish entirely without the pre-amp. With my linear amplifier in circuit I can work almost anyone I hear, including ones running low power. This suggests that the balance between my receive and transmit performance remains good.

From time to time I turn off the pre-amps just to see what happens. Terrible. I doubt if I could do without them now.

Of course the results will depend on what coax you are using, the performance of the pre-amps and the basic ability of the radio you are using. However, for serious DX on 144MHz and above I think masthead pre-amps are a necessity.

If you use a multi-band antenna with a single feed you can get wide band masthead pre-amps, though of course single band versions are likely to perform better. You can buy various makes of pre-amp, ranging from very high performance ones down to fairly modest ones, with prices to suit. Mine are on the modest side, but still worthy of use. It is something worth considering, I think.




Friday, 15 February 2019

Of tropo, soldering and unusual work

I have been off the air for a while - the dreaded house decoration I mentioned before finally came to happen. I tried to avoid it, but there was no stopping it. So the shack was completely dismantled, everything in the shack was cleaned, and then dumped back where it had been dumped before. Well, not quite, my shelving has been dismantled and strengthened to take the weight of two Linear Amp Gemini amplifiers, which previously caused the top two shelves to sag. A stout piece of dowel now supports each shelf. Expensive stuff, good dowel, so this takes the form of a brush shaft sourced from that well known speciality emporium, "Homebase". That place definitely gets my brush shaft recommendation.
Strengthened shelving unit with added brush shaft and corner plates
The decorating original plan involved moving the shack desk, which did happen, and also moving the amplifiers to near ground level. In the event the amplifiers have remained where they were, but they now seem to be more or less level on a non-sagging top shelf.

Of course, as soon as this work was complete, one of the amplifiers (the 2m one) developed a fault, or rather showed again a fault it has been developing for some months. Thus it returned to the manufacturer for repair leaving a big gap in my 2m armoury.

I have been accused sometimes of writing too much - but regular readers know this cannot be true. It cannot be true because I have said it isn't true at great length. Nevertheless I did write a very long piece about linear amplifiers, preamplifiers and sequencing which I have decided to save for another day. Never mind the theory for now, what about the results?

With Hepburn's tropo predictions showing hopeful signs for yesterday (14 February) - a link to Hepburn is on the sidebar - there were also more signs of a possible lift in conditions. When somebody you respect suggests you should be prepared you take note, and then when two others of the same standing do the same, then you are obliged to get ready. And indeed, Colin GM0HBK, Jeremy, M0XVF and Dirk PA3FMP all suggested I should standby for better conditions. But I had no Gemini, which meant no working pre-amp too. So I needed a Plan B.

Without my Gemini 2 amplifier my hastily assembled Plan B was to use the parts I recently said I was stockpiling for some other, undefined, project. Viz, a second Down East Microwave (DEMI) sequencer, a "Bias Tee" from SSB Electronics, and to add to those my old Microset SR200 200W 2m linear amplifier. This assemblage would get my masthead pre-amp going and get me running enough power to work some DX. The only snag was that, starting yesterday morning, I had precisely nothing working. Some corners will have to be cut.

I had already got the Microset fixed in theory, although it had never been tested. I had called on the assistance of John, G1VVU, to investigate it. John quickly found that one of the output devices (it uses 2 2SC2782s) had gone short circuit and seemed to have died. I was able to find a new one fairly easily, in fact two, as it seemed best to change both of them. Well, not once we found how tangled the inside of the Microset was, so we changed the faulty one and kept the other new one as a spare. So far so good.

Apart from the fact that the Microset doesn't have a PSU, fans nor even N-type sockets, it should replace the Gemini fairly easily. The PSU is not such a stretch, as it only draws about 20 amps on full power. Then come the fans, so I dug out two dusty 12cm computer fans and mated them to a temperature controlled (27 degrees C fixed, but good enough) switch. Luckily I had boxed the temperature controller up with suitable sockets and so the cooling side of things could be organised quite easily. It isn't right that a transistorised amplifier should be perched on top of its own power supply as the heat of the PSU will rise, but for now that will have to do.
This jumble is the restored Microset SR200, fans, PSU and (left) the homebrew fan controller
Getting a replacement system going that morning was "the art of the possible". That stack of gear is not tidy but it worked for now.

Next task get the sequencer working. No need to explain what a sequencer is, that is for the later long-winded posting. (Is this not a long-winded posting?). Anyway, you need one if you are going to use a linear and a masthead pre-amp and not blow either or both of those up. With the DEMI sequencer this involves wiring a D15 socket and working out a wiring loom. No time for niceties, I got a bit of surfaced wood the right size for the shelving, stuck the sequencer to the wood with Velcro, stuck a chocolate box connector strip to the board with double sided tape and got soldering.

Oh I hate soldering D15 plugs. Actually, I hate soldering any plugs. I tried to cut a VGA cable in two to save the soldering, but despite it being an "all wired" cable, one pin (pin 5) was not connected. So soldering it was. Mrs FVM, who recently had cataract surgery, donated me her temporary +2.00 reading spectacles for the close work. Working out the sequences and testing the operation is fiddly. Once again lack of time meant a temporary arrangement and here it is photographed while I tested it...
Down East sequencer and wiring tangle under test, with the Bias-Tee lurking in the background.
Once I got this up and tested I even found time to organise the wiring, give it some strain relief and put the covers back on the D15 socket. Not before I got the wiring mixed up - why do I always think a D15 socket is a D18 socket with 6 pins on each row, and then get the rows upside down too?

The result is a total lash-up, and it looks awful. Stuff piled all over the place. The sequencer is on a desk at the other side of the shack. There is an SWR meter perched drunkenly on top of some books. But it was more or less ready when it was needed.

OK, everything working now, but will there be any lift conditions to justify all this work?

Due to the shack reconstruction I had not had a QSO since 25 January. I got basic operations going again in the "new" shack on 11 February with the Gemini but it was showing a fault. The Gemini went back to the manufacturer on the afternoon of 13 February. Thus it was only on the morning of 14 February that I started Plan B. Was there any point? Wouldn't the Gemini be back soon, and would all that work be justified by any DX before then at all?

First contact with the Plan B set-up was on 2 metres at 15:54 on 14 February to Dan OZ1BEF. I can work Dan in most conditions, but still that was positive sign. It proved that the Microset and my lash up were working.
2m FT8 stations worked at GM4FVM, 14 Jan to 12:00 15 Jan 2019
As usual, click the image to enlarge if you need to.

I have to say that I was rather pleased with that result. Could I have worked the same stations without all the work to get the temporary linear amplifier working? Well maybe, but the extra power does help get you noticed. Once they turn their beams it becomes easier and that extra clout means they find you while they are beaming at more obvious targets to the south of me. The linear was secondary, I needed the sequencer for the masthead pre-amp, so I had to do it all anyway.

Before anybody asks, yes both the Microset and the pre-amp have RF VOX and should, in theory, work without sequencing. That is very risky but more to the point, the IC-7100 objects to powering up into either RF VOX and so it cuts the output power. I did try briefly without the pre-amp it it was terrible.

70cms brought a new station worked plus one I had contacted last year. Both are much appreciated
70cms FT8 stations worked at GM4FVM, 14 January 2019
Both these 70cms contacts were the result of the stations suggesting we move band after a successful contact on 2m. This just goes to show that there are plenty of 70cms contacts to be had if we could only find them. DK0HAT even suggested going up to 23cms for a try, but sadly that is something I cannot do ... yet ... but even on 70cms he was new square.

During the opening there were long, strong, ducts forming. For example, Charly, DF5VAE was heard here on 2m for over an hour, and at stages registering +10dB on the WSJT software. That is a good 30dB over the minimum level I can reliably work anyone. I could hear Charly's signal loudly on the loudspeaker. Likewise, DK0HAT was heard calling CQ on 70cms for a long time. There was nobody around in GM to work them, which was a pity.

At the same time, at the other end of the tropo spectrum, there were short openings into various areas which came as a complete surprise. Unlike the ducts they were gone as soon as the contact was complete. SP6MJ calling me was a bit of a shock. Conditions held up just long enough for him to wait patiently while "Auto Seq" on WSJT-X answered and worked another station before reaching him. Then, contact complete, he vanished. SP6MJ, in JO81, was a new square on 2m and the best DX so far in this opening at 1370km. Several other 2m contacts contacts were near 1000km.

Is it over as I write? Well I have just worked OZ1CCM on 2m and he is clearly not beaming my way as I can hear him off the side of his beam working Polish stations. I also just worked OZ9PZ on 70cms after he came back to a random CQ call. He also asked me to go to 23cms - is there a pattern emerging here?

Was it worth all that effort to set up a ramshackle pile of gear to work one 18 hour period? I think so. 19 QSOs, 8 DXCCs, two new squares, and a test of my shaky constructional abilities. This hobby has to test us and I think it should never be easy. Certainly, I could have just sat back and watched a re-run of "Rising Damp" on the ITV hub, but that can wait. Radio happens when it happens.

I enjoyed jumping in and getting something sorted out, even if I have to take it all apart this afternoon. Eh? Well, the Gemini was only away for 36 hours - it arrived back at 11:00 this morning. Of course I did not know that in advance.

Thanks to Colin, Jeremy and Dirk for alerting me. The moral of the story, as the great Otis Redding almost sang on  "(Sittin' on) The Dock of the Bay" ... "I can't stop doin' what three people tell me to do, so I guess I'll never remain the same".

Now, I must unpack the Gemini and pull Plan B apart.