Monday, 25 July 2016

Experimental Icom IC-7300 keypad

OK, I will concede this - my first attempt at it - does not look very pretty...
erm, but it works!

The idea came from looking through the enormous IC-7300 handbook. In there it explains that, rather than using the touch screen to summon up the "voice keyer" you could do this using a keypad.

The voice keyer allows you to make repeated CQ calls, for example. Whilst you can record 8 different calls, only 4 are available from a keypad. I actually only need two on a regular basis, "Long CQ" and "Short CQ", plus (occasionally) a long CQ call which invites calls on both 4m and 6m bands, for cross-band QSOs.

Once these CQ calls were recorded onto the SD card I found that the only way to play them was to keep the "Voice" screen on the display. This narrows the useful screen, makes the waterfall smaller, and means that I keep pressing the same points on the touch screen. To prolong the life of the screen, and to make the display bigger, I thought that the keypad would be useful.

As the handbook says "The External Keypad is not supplied by Icom". Indeed, but it is not hard to build one.

I was strengthened in my plan when I heard that David, GM4JJJ was planning to build one too (though I bet his will look better than mine).

My initial plan was to drill a hole in the base of my desk mic and mount one centre-sprung mini-toggle switch. That would give me access to two pre-recorded CQ calls. Then it emerged that the keypad could also send pre-recorded CW messages, and then I might need four options. And I also noticed that I could add an up/down VFO switch too. Although up/down tuning using a toggle switch does not appeal, I could use it to change memory channels, which is something I do a lot. So we had expanded to six push buttons, or three toggles, or some combination of that, plus five or six resistors, and then it emerged that I would have to rewire the desk mic as it only had a three core cable (well, 2 insulated cores and a grounded screen).

Plan two emerged and things had changed to envisage me building a mock-up keypad in a plastic box, at least to test whether it worked and would be useful. I had four miniature push buttons and a toggle switch from Maplin left over from another project. I also had a new plastic box also picked up at Maplin for some long forgotten project, but rather than use it I had an identical box which had banana plug terminals. This was out of use (I discovered that fuses were a good idea on my distribution system).
What I had assumed about this box was that the holes were in the right place. They aren't. I might have been better making my own holes in the new box, but I noticed this too late. So my four push buttons are not organised in a perfect square. Hey, this is just an experiment.

I ended up using the bottom of the new box and the top of the old one - too complex to explain.

The circuit is simple, as per the Icom manual.

As usual click the image to enlarge if you want to read it.

I already had the resistors, and even one to add the up/down switch. I decided to build a test version with a (right angle) 8-pin mic plug from the parts box. I had some 1 core + screen cable. The whole thing worked perfectly.

Then I decided to organise the 3 core + screen cable. 4 core + screen was cheaper so I ordered that. As I was waiting, I might as well order a new straight 8-pin mic plug and a socket to make the thing a "feed through". By mounting the 8-pin socket in the box I can use it with any microphone. As I had ordered four core cable, I had an extra line. I would be able to take an extra feed from the rig into the box, which could be the +8 volt one. I might want to add something else in the box later (like a pip tone?). I decided to move on to this version as the elements would allow me to test it on the air.

So that is where it stands now - still in the test plastic box, 8-pin plug from the rig, 4 core cable into the box feeding a socket on the box into which the mic is plugged. The Pin 3 from the rig goes to the resistor network. I can select up, down, or any four of the pre-recorded messages. If the rig is on SSB the buttons select voice messages, if it is in CW mode they select CW messages. Thus the cryptic labels I put on it.

As well as SSB and CW recorded messages you can also use RTTY ones. Not much chance of me doing that.

Now instead of seeing this screen and having to press the buttons on the screen ...

I see this screen and use the keypad ...
More waterfall, more spectrum scope, less pressing the same spot on the screen all the time.

I think this project was worth it and I expect to use this keypad a lot. Whether I will try to cram it all into the mic base is a bit doubtful. If not it would benefit from a neater box and better labels. But the point is it has been proved to work, which was the object of the exercise.

73

Jim
GM4FVM

Saturday, 23 July 2016

Poor conditions so time to fix antennas

"The bands are bad this week" I hear them say.

I doubt if they use the bands I use. Still, I nod in agreement.

I also doubt if "the bands" operate as a single unit. That is the point about them. They are bands. Slices of spectrum. The things that make them interesting are their differences. In reality, they hardly ever work as a symmetrical unit. Some of them are at their best when the sun spot cycle is at its worst, and others are affected the other way.

So I need to navigate this carefully. The bands I use have done badly recently when it comes to Sporadic E. From here anyway. The RSGB News says there have been Es openings, but not here. Maybe they don't cover here in their news. I had one contact in the book between 17 and 23 July - and that was meteor scatter.

I associate this time of year with working the Azores on 4 metres, or days of Es over the Baltic, with 50 stations worked in a day and me welcoming the sunset with a sore logging hand and a frog in my throat.

If Es does not work, the bands I tend to use - 6m, 4, and 2m - are often saved by the other esoteric modes I use. Meteor scatter has brought me two contacts in the past 25 days. The last aurora contact here was just over 6 months ago. The last tropospheric ducting period was 6 weeks ago. So I am claiming that "the bands are bad".

This makes time for organising the antennas.

After complaining that I had made no progress on moving my 6m antenna onto a separate mast, yesterday I moved my 6m antenna on a separate mast.
The six metre HB9CV is in the right foreground. It was there before, but then it was mounted on a peely-wally pole. Now it is on a nice guyed pole which also supports the 40m dipole. The antenna is about 6 metres above the ground and stands clear of the ridge tiles. It is actually slightly higher than it was before it fell down a while back. Or rather when I dropped it a while back. The lightweight Conrad rotator, which spent a while with GM6ZFI, has returned to rotate it.

In the distance on the left is the main mast (not cranked up in the photo). As a compromise, a Diamond x30 has appeared on the top of that mast. This replaces the Moonraker vertical which was previously on the right hand pole. The x30 is a fairly modest antenna which works as a half wave on the 2 metre band. I would rather not have it right above the 2m horizontal beam, but I do not have any where else to put it.

Immediate results from the new location for the HB9CV were good:-
That was a new 6m DXCC from here on JT65 (though I have been heard in 4X4 on 4 metres). However, the new antenna location is producing those streaks on the waterfall. These are birdies which were not visible at the previous location and so there must be some source of interference over there. Some switching power supply somewhere I guess.

These changes mean that, for the moment, the 6m line has lost its stub filter. I must sort that out.

But let us hope that this antenna set-up actually last for a while.

I am getting fed up chopping and changing it.

You all must be getting fed up reading about it.

73

Jim
GM4FVM

Monday, 18 July 2016

Stub filters/ diplexer for 50MHz and 70MHz.

When I started on VHF from this QTH I used a variety of home brewed antennas for 50MHz (6 metre band) and 70MHz (4 metre band). These were mostly variations on the theme of the HB9CV with added reflectors and directors.

The wind here soon took its toll and I moved on to a sturdier commercial 6m/4m dual band beam. This would only fit if it had a short boom, and I eventually became disenchanted with its performance. I was never really happy with the feed arrangement whereby the 4m "driven" element was parasitically energised by the 6m one. Psychological doubts were raised by this - "how can this work when my co-ax is not connected to the antenna?". Silly doubts I am sure, but the other thing was that if I moved the 6 metre antenna to a separate mast I could make the 4m one longer ... so I put separate antennas on separate masts.

During the time that I used the dual band antenna I kept separate rigs for each band. I had become used to monitoring both bands at once and of course this is the area of amateur radio that I enjoy most - chasing the propagation between the VHF bands. To allow those two rigs to feed one antenna I built a "stub" diplexer.

The basis for the stub diplexer was an article by John, G4SWX, in Radio Communications (I believe it was the March 1996 edition, but it was spread over two editions of the magazine so I am not sure about that). David, G4ASR, was very helpful and he was able to provide more details. I broadly followed the plan in the article apart from substituting PL-259 plugs for the soldered joints and using RG-213 co-ax. Afterwards I wished I had used "N" types, but the extra cost would have been considerable.

As a general idea, two quarter wave co-ax stubs make up each of two elements. The stubs are organised as a "PI" type array with open quarter wave (at the rejected frequency) stubs in parallel with a quarter wave of the wanted frequency between them, and then with a balancing quarter wave at the rejected frequency to the common input.

In my case I mounted the whole thing on a wooden frame. The resulting monster was 3.2 metres by 1 metre and therefore would not fit in the shack. I eventually mounted it in the attic. Two runs of co-ax ran to the filter and then a single feed to the antenna. This rather "Heath Robinson" device worked 100% perfectly.

Now I made this in the days before I had a proper antenna analyser and before I had a good razor saw for cutting the co-ax exactly to length. I cut it to plan and did some simple tests with two hand helds, two SWR meters and two dummy loads which seemed to suggest it worked. The 6m trap rejected the 4m signal which followed the resonant path to the antenna rather than the filtered one into the front end of the other rig, and vice versa. In the end there was no alternative but to connect the two main rigs to either end of the thing and press the PTTs, but neither rig  blew up. In fact it worked faultlessly for a long time. No moving parts, no lumped components to blow up, nice simple co-ax engineering.

After I gave up on the dual band antenna the diplexer stayed isolated in the attic - it had been assembled up there and it would not fit back down through the trap door. However, some of you may be aware that I had an "incident" with the 6m antenna, and it is now temporarily on the same mast as the 4m one. Predictably they are too close and operating on either 4m or 6m blasts the other rig and threatens to blow up a front end.

So I hit on the idea of separating the two elements of the diplexer and using them as trap filters - a 6m trap on the 4m rig, and a 4m trap on the 6m rig. Unscrewing the wooden filter frame from the roof timbers caused it to break in the middle, which was handy enough (I since sawed through the frame at the diplexer feed point and made two elements shaped like the letter "P"). I had some confused idea that I would not need the matching length of a quarter wave at the rejected frequency, but a few tests with the antenna analyser put me straight.

The ARRL Handbook warns that the MFJ analyser is not accurate when it comes to tuning stubs and they seem to be right about that. I took their advice and allowed for up to 500kHz error, and at that level of resolution the filter elements seem to be very good stop filters.

Once I got them down from the attic and sawed them in two, tested them, and got ready to try to fit them into the shack I took a couple of photos. Here is the 4m filter, which rejects 6m ...
As you can see, it is still pretty vast even after having been separated from the other element. The 6m filter, which rejects 6m is much smaller but still quite a monster ...
I did eventually get them into the shack and somehow got them hidden behind furniture. Then came some odd results when I tried to test each one separately, but when I put both of them into their respective antenna lines they worked quite well.

I can now transmit on either 4m or 6m without the S meter on the other rig moving at all. There is a slight increase of noise noticeable, but it is not significant. Hopefully, this will save the front ends, and in particular the preamp on the 4m linear. It is hard to calculate the insertion loss but results on that front will emerge over time. However, when I used them as a diplexer there was nothing apparent after hours of complex tests.

These elements were built rather roughly and I am sure that I could do some trimming to make them better. The 4m filter raises the SWR from 1.1 to 1.4, whereas the 6m one seems to make no difference at all. On the other hand, surely I do not intend to keep both antennas on the same mast, and once I separate them again our old friend "Inverse Square Law" will render the filters unecessary again. Or will it?

Just for now I shall leave things in "test mode". These tests have a habit of becoming permanant features.

The question which needs to be answered, apart from where the 6m antenna will eventually end up, is just how important is being able to monitor both frequency bands anyway? Yes, I do enjoy it. I do not need to have enough isolation to transmit on one and listen on the other (though now I do have that). What I want to do is to listen on both at once whilst occasionally transmitting on either. There are other ways of doing that. A rig with two rx slices might work, for example. Maybe I would still need the diplexer for that. Anyway, come on Icom and the others, get working.

Stub filters are often overlooked and can be very effective. I doubt if a lumped component filter would be able to separate 50 and 70 MHz effectively, and even if it could the losses would be higher and the power handling ability would be lower. At 50MHz rejection the stub filter is rather large (!). I have seen photos of these filters with the co-ax coiled, but I feel that would open to the door to too many variables. Coiling RG213 is tricky and thinner co-ax has drawbacks. Despite the consequences of all this making for two very bulky devices, I still reckon it is worth it.

As a bonus, the 50MHz filter in the 4m lead provides some attenuation of my 144MHz signal too. Open ended stub filters work at odd harmonics too, and whilst this would include 150MHz there still seems to be some reduction in the impact of transmitting on 2m. It does not have any effect the other way of course, so if I want to reduce the 4m transmission effects on the 2m rig I will need to add another filter. Pass me the hacksaw ...

73

Jim

GM4FVM


Tuesday, 12 July 2016

Mirfield Quad Band Vertical - I cannot even give it away

WARNING - This posting ends with complex and obscure surreal metaphors based on the lyrics of a song released in 1968 and a mysterious and secretive baker of fruit filled sweet rolls who vanished at the same time. If you do not understand the references you weren't around in the aftermath of the  Summer of Love.

This is probably my last posting about this antenna before I break it up for parts.

As you may recall this antenna seemed like a good idea but the SWR was high and the performance not good. So I sent it back.

When it was returned from Mirfield, inside I found a note telling me the SWR results I should be getting. Nothing else seemed to have changed and I had already explained when I sent it that I could not get those SWR figures. So really I was not much wiser.

Being at a loss and knowing that GM6ZFI was looking for a vertical for 2m and 70cms I suggested to him that he might like it. I explained that I had not tried it much on 2m or 70cm, but the SWR was better there and it should work better on the higher bands. At least the length of the antenna then was somewhere near a multiple of a quarter wave.

Doug sped off with it and put it on his mast. Immediately his signal strength here dropped from S8 to just opening the squelch. I could just about hear him but I could not make out anything he was saying. It was the same story with my signal. After a few days Doug returned it to me saying that he could not get any acceptable results with it. Even though I had given it to him, he would rather return it as it was no use to him.

After he took it down and went back to his normal set-up I could work him again fine.

It was interesting to be on the receiving end of an antenna experiment, but a bit of a pity that he would not even take it away for free.

Doug's advice was that I should return it to Mirfield. I have already tried sending it back and it just came back after 6 weeks with the note in the package telling me what I should be getting. No amount of experimentation here came anywhere near those SWR figures.

So I guess I am stuck with it. No point putting it up, so it is leaning against the garage wall still in the cardboard tube it arrived in ...

I cannot really see the point in trying again. Why should I send it back again? I have already paid to send it back once and when you take into account my drive to the Post Office, and what I might otherwise do with the time I would spend on it, I guess I can only write it off.

I need to remember that if something looks too good to be true it probably is too good to be true. Antennas as short as a quarter wave are not going to be very good, and ideally when it comes to VHF verticals, they need to be longer than that. Most people use half waves, 5/8ths or longer co-linears.

If it had worked for me, it would have been the shortest vertical I have ever built or used on 2m, and it was supposed to work at 50 and 70 MHz despite being 1.2m metres long. Worth a try I guess, but it simply lacks the performance I need.

I might move it round the corner inside the garage, and eventually use up the brackets and fittings for home-brewing. What a round-about way to get antenna hardware.

However, like the cake in MacArthur Park, perhaps I should just leave it out in the rain.

It does not really matter how long it took to bake it. I don't like the recipe. I prefer Fig Rolls anyway.

Come to think of it, the Donna Summer version beats the Richard Harris version any day.

Does Jim Figgerty have a callsign?

73

Jim
GM4FVM

Sunday, 10 July 2016

I have returned, plus the RSGB Es prediction problems resolved

I am back after a short break without radio.

Here is a photo of me looking fairly grumpy on the quay at Oslo, in Norway.


I did not really have anything to grump about, I just seem to look like that nowadays.

Before I left I had meant to post an update on the RSGB Sporadic E predeictions. I did not get a chance to get it posted so here it is a bit late.

A week before I left they said this:-

Sporadic-E may be poorer next week as the main Atlantic jet stream activity has already migrated north, leaving much of central Europe under a much slacker pattern. The absence of active jet streams over Europe probably means that one of the main Sporadic-E triggers, gravity waves, may be missing or reduced. These waves propagate up from the turbulence of the jet stream at 12km height to the E region at 120km.

This absence will make Sporadic-E hard to come by except perhaps for the more northern paths across to Scandinavia where the jet stream may be slightly more active.

 So, poor Es and any there is will be across to Scandinavia.
Here is the result I had in that predictions period:-  


You may call me picky, but Scotland to Portugal is not really what I would call Scandinavia. I did have one contact which was North of East, Finland, but all the rest were in the South East quadrant or Portugal. And if that is poor Es due to a lack of gravity waves, I would settle for it any day. That is definitely good in my book.

I now have a working method to deal with these RSGB predictions. I found that just ignoring them did not help me. Much better is to read them and do the opposite. If they say "poor Es", then expect good Es. If they say, "Northerly paths", expect mostly Southerly paths.

This new system has been working well for me for a couple of weeks.

Regular readers know that I have been complaining about the RSGB reports being wrong for ages. It is not just this one week. But now I know how to use them!

I know they say "may be" poorer, but why state predictions if they are not fairly confident that they will happen? Now that I have found the key as to how to use them I am doing rather well towards my targets. 

I am not saying that jet streams and gravity waves do not play a part in understanding Es (though I suspect that they have little to do with it). I do not have the proof to say that. However, over the weeks and months of observations I can say that the predictions based on the idea that they do play a part seem to be entirely wrong at this QTH. Indeed, they are a good indicator of the opposite.

So thanks for the (inverted) help, lads. 

There is a difference between saying some factor influences something and making predicitons based on that.

I used to think that wrong predictions were worse than no predictions. Now I realise that consistently wrong predictions can actually inform me about what isn't going to happpen, which is useful information in itself.

Normal service is resumed!

73

Jim 
GM4FVM