Triband HF dipole? No, a G4MH driven element.

I am, and have always been, A TRAITOR! 

No, no, that's not right. [Mmm, it might be Jim]

I am, and have always been, interested in propagation. [That is better] 

And I have been particularly interested in VHF/UHF/microwave propagation. So that means 30MHz upwards as far as my pocket will stretch. But recently I have become aware that there is not much to look for at, say, 30 to 32MHz, whereas I could possibly find lots to listen to from 28 to 30MHz. That might hold some clues for me.

I started a couple of months ago by listening to FT8 transmissions on 28.074 using my Yaesu FT-710. I had no HF antenna to connect it to so I decided just to use anything I had, which turned out to be a 70MHz ring-base vertical! Despite the limitations this worked surprisingly well and proved the concept that this was worth doing.

The object of the exercise is to look carefully at what propagation is available at the top of the HF bands and compare that to how things are progressing on 50MHz. Sometimes I also check 40MHz. In particular I am trying to learn better how to spot F-layer propagation and compare and contrast that with what is happening in the E layer.

Once it seemed this was worth doing I needed something better for an antenna on 10m. That would also allow me to return to using the 70MHz vertical on 40MHz (!). In previous periods of low solar activity I have used one or other of a pair of Sirio vertical dipoles, one was 5/8th wavelength, the other a half wave. These seemed not to work so well, perhaps because they can only be located where they are surrounded by buildings and with ground sloping upwards away from them. I also have an "end fed half wave" (the first part of that description is true, the second part is fantasy) but it has only been mounted close to the ground.

So I began to think of an antenna which would fit on a mast and thus have some height and useful directivity. Sure enough, I used to use just such an antenna at this location when I first moved here.

Driven element of the G4MH mini-beam at GM4FVM on 17 February 2011

Above the HF dipole was a 4 element 2m yagi and an HB9CV for 4m, and above that is the dreaded 70MHz ring-base vertical. Below it is a Yaesu G-600 rotator on the Tennamast.

Some background is needed here. Back in about 1980 I bought a G4MH 2 element mini-beam. This was mounted above a HAM-M rotator on chimney lashings at GI4FVM in Finaghy. It certainly caught the eye of local CBers at the time. Later, after I had fallen out of love with 20m, I sold it and bought a 2 element Mosley 10m and 15m beam and a Jaybeam 8-XY 2m yagi which threatened to pull the chimney down (but never did). However I had fond memories of the G4MH.

About 20 years ago, after moving to my present QTH, I spotted a G4MH for sale about 150km to the south of me and in a fit of nostalgia I bought it and put it up here. It was certainly very effective, but the move 150km north to a windier location proved too much for the plastic block which held up the driven element. This quickly broke and I replaced it with a sturdier crosspiece made of 35mm thick wall alloy tube held by four Vine plastic mountings. That added to the weight and so, wary of the potential issues, I put up just the driven element which also worked fairly well. It is in this form that you see it in the image from 2011.

Some explanation of the G4MH idea is necessary. Jim Fish, G4MH, sold these mini-beams and his idea survives in 2 and 3 element commercial triband mini-beams still on sale to this day. The idea is that a series of spokes add capacitance to the ends of the elements allowing the length of the dipole to be shortened to under four metres. First there is a coil wound round a helical groove in the extreme end of the elements. The inside spokes then are for 10m, then there is more helical coil before spokes for 15m and then more helical coil and more spokes for 20m. Basically the coil and the spokes act as a trap for the higher bands. Originally sold as a two element beam the boom was shorter than one might expect for a 14MHz antenna and thus the gain was not great on 20m, but I found it excellent on 15 and 10m.

From what I recall of the original one I have in the 1980s, when you bought the antenna you got a  box with the coils wound on a plastic former, a large number of brass spokes and the central plates which supported the elements (one plastic and one alloy). Maybe you got the central mounting too. Then you had to source the aluminium for the elements and boom yourself, cut those to the correct lengths and build the thing. Tuning the elements by cutting the brass spokes was a dreadfully fiddly process. You needed to tune each band in turn looking for minimum SWR, but that depended on the height above ground. As mine was chimney mounted this was impractical but you could put it on a low mount, get it tuned and then apply a rough formula of length of cut altering the resonant frequency by some sort of estimated amount. All very hit and miss. I cannot recall how you were supposed to tune to director.

You had a few extra brass spokes, which could be useful if you over cut them. However, you needed to keep them in case you broke some spokes as those were open to the elements and bird strikes. And indeed I did break some, and then getting the broken base out of the brass ring on the plastic former was a pain and involved cutting a slot in the spoke and trying to screw the thing out.

If all this seems like too much effort, the thing worked remarkably well for its size, and not many people had tri-band beams in the early 1980s 

I have a photo of it here as a two element beam, but I cannot find it at the moment. It was captured by Google street view on one of their earlier visits to this area, but that has long gone from their site.

For this purpose I am happy just to get the driven element up in the air and see how I get along. After all, the antenna is in the garage and why not put it up? It needed a bit of fettling have been in pieces for many years.

The GM4MH driven element being assembled in the GM4FVM garage

My main worry as I put it back together again was whether it would stand the wind here now. The plastic mounts I added are now a lot older, though they have been inside the garage in the meantime. Everything else seemed to be in good order. I noticed that the boom and the director are also OK except for one broken spoke, but I have no plans to put this up at this stage (or maybe at any stage given the 23cm antenna is already on that mast too). 

The driven element is 3.4m long and for the same direction of radiation as the similarly long 23cm antenna on my Tennamast it has to be located at 90 degrees to the yagi. This was a bit tricky to achieve as back 20 years ago I mounted it with the 1.5m boom on that orientation. Being twice the length it could not be mounted that way now due to our greenhouse being in the way. However, with the yagi at 45 degrees to the ground the G4MH at 45 degrees the other way it all fitted fine.

Anyway, up it went in due course and despite my doubts it works rather well on 10m and even 15m. The resonant point changes depending on the height of the mast, and the SWR can rise from 1:1 to about 1:2.5 when it is down. However this is well within the range of the 710's ATU. In any case I expect mostly to  be listening on it and it has got to be better than the lash-up which went before. On 20m I tested it but got a lot of RF into the shack. Given that I am not interested in 20m I shall leave that problem for now.

G4MH driven element back up on the Tennamast on 19 October 2026, with 23cm yagi above

 

Of course I could not resist testing it with the FT710 and 100W. So far I have worked PY, TN and TL, plus assorted Ws and European Russians, with the usual array of European stations. On 15m I worked YV. Not a bad performance so far and we shall see how we get on over the Winter.

Speaking of the Winter, I had some doubts about how the aged antenna might manage high winds. In later years G4MH kits were sold by Wimo and they claimed their kit could cope with winds up to 125km/h. I had my doubts about that too. Then along came storm Boelo which produced the lowest barometric reading I have ever seen -- almost pushing the pen off the bottom of the paper. The UK Meterological Office predicted winds of up to 130km/h in "exposed coastal areas". Ventusky estimated the wind here at 124km/h (77mph) and the antenna survived. Of course with the mast lowered the antenna is well protected from most winds.

This is an attempt to produce a cheap receiving antenna to test propagation on 28MHz. Ideally I would put up a 10m Moxon which no doubt would produce much better results. Nevertheless, for no expenditure save for a couple of cheap coax plugs it seems to be working well.

Now it needs to produce some useful results for comparison.

73 Jim

GM4FVM

The joy of N-type plug

At first, I did not like N-type plugs. As someone whose first transmitter featured a "Belling-Lee" socket I even found PL-259 plugs a bit technical. The main benefit of the PL-259 seemed to be that unlike the Belling-Lee it did not pull out of the back of the rig by itself and it tended not to melt so quickly if you transmitted for too long. In fact when my earliest the second-hand Amphenol 259s ran out, the cheap new replacements could melt just like a Belling-Lee as the central bush was often not well made.

As time went on my preferred frequencies went up and even the trusted PL-259 fell out of favour. After all, it was just a shielded banana plug. The fundamental problem was that it failed to maintain a constant impedance whilst if I used a 50 Ohm N-type that could be ensured (if I assembled it correctly). After a famous incident where a vertical antenna sprang an internal leak and rain water passed through the SO239/PL259 combination and down the coax, rotting the expensive cable as it went, I had had enough of PL-259s. Even though I had encased the connection in self-amalgamating tape to stop any water getting in from the outside, there was nothing to stop it passing right through the inside of the plug. 

That joy of N-type includes some confidence in the impedance, lower loss, some degree of water protection and generally less loss. Then they can handle much more power. Even though the cheap inners of melting 259s have gone, even full-spec 259s have lower power handling, especially at higher frequencies.

If you want to test the frailties of PL-259s at higher frequencies, try stringing a few back to back in a single run of coax and watch the SWR go up and up.

Anyway, VHF and higher frequency equipment started appearing with N-types as standard. There was always the option of using converters. These will allow you to connect a PL-259 plug to an N-type socket, and even vice-versa. Not a good plan, apart from lashing things up occasionally to test them. It is a simple issue: by effectively converting an N-type which the manufacturer has carefully specified to get maximum performance you are reducing the specification to a PL-259 level which they had deliberately not used to start with. If your linears etc, further towards the antenna, also used 259s you were heading for even more trouble.

So at some stage I decided to ditch all the comfortable old ideas and, as far as possible, out went the converters, RG-213 coax, PL-259s and so forth to be replaced with Hyperflex or Ultraflex 10 (U10) for main antenna runs, Ultraflex 7 (U7) for ancillary stuff, and N-types wherever I could.

It quickly became clear that compression type plugs were the best. Expensive Messi and Paoloni (M&P) in exposed places, but often other makes for inside or low power use. And at first I did not like compression plugs.

Parts of an N-type compression plug

On the left is the blue stopper to prevent the pin falling out in transit - you can keep it as a dust cap. Next is the barrel, followed by the centre pin and the insulating bush. Then you have the collar which pushes under the coax outer sheath to make contact with the braid (it fits the opposite way round but it kept rolling away so it is shown facing the wrong way in the photograph). Then you have the brown compression ring with a washer on either side. The left hand washer is smaller and butts up against the cut end of the sheath (the braid it trapped between it and collar then trimmed). On the right of the compression ring is the most crucial washer in that the plug will not go together properly if it is not in place to allow the compression ring to be compressed by the sealing nut on the right. The barrel has a flat on it and the sealing nut has a nut end so that you can put on two (usually 18 or 19mm) spanners and tighten the whole thing up very tightly thereby sealing it rather well while at the same time compressing the ring tightly, producing a reproduceable low loss fairly watertight plug.

This all looks simple so what was the problem? I mean, unlike 259s of an earlier era, there was no need to solder the braid to the barrel of the plug (though 259 compression types are now more like this). The thing was, I did not know what I was doing. It was not until a retailer put a video explanation on their website that the penny started to drop. Then eventually M&P began to put an explanatory card (with 13 steps!) which showed you exactly what to do. 

I had to learn the hard way. The plug is carefully machined and all the bits need to be perfectly assembled. Without the (otherwise apparently pointless) washer between the compression ring and the sealing nut it is very difficult to screw the thing together, and it will not be watertight. And then we come to soldering the centre pin to the centre conductor of the coax - never an easy task for me. In that first video I watched it gaily stated that if you place the hole in the pin vertical and place the soldering iron on top then the solder will happily sink into the hole as if by magic. Not in my world it doesn't. And M&P suggest only having the soldering iron to the pin for two to three seconds. However, over time I have got better at this and by now I must have made up several dozen N-type plugs. They are not cheap, but they are very good.

So what brought this back to my attention recently was when making up the coax connection to an antenna which must be 50 years old but which has been in the FVM Garage Dead Antenna Storage Facility here for 10 years or more. More on that antenna, if it works, later, but for now you can take it that the main specification for putting this antenna back up was that the whole project had to be done at no cost. Thus, not only was the antenna old, but the coax was U7 recovered from an earlier project which was to be connected to some existing U10 which runs into the shack. And as the U10 had an existing N-type plug on it then the recovered U7 had to have an N-type too. The project is low frequency and low power so there was no real need for N-types but I was not going to change the N-type on the existing coax for no good reason either.

For this purpose I selected one of M0MAT's plugs which work for the H7 coax I was using. That is the plug in the photo. To start with I did all the right things. I pushed the sealing nut up the coax, followed by the wider washer and the compression ring. I even wrapped some insulating tape round the coax to stop them falling back out again as the coax was hanging downwards (these bits can fall off and leave you having to take the whole thing apart again if you are not careful). Then I trimmed back the coax outer sheath 10mm, slid on the narrower of the two washers, peeled back the braid, pushed in the collar under the braid and trimmed back the excess braid. Then I carefully trimmed back the inner of the coax right back to the collar ready to solder on the centre pin. At this stage I could take off the piece of insulating tape which was preventing the other parts from falling off the coax as the collar would now hold everything back up the coax.

Being a Good Citizen I then tidied up and took the cut sheath, used insulating tape, bits of braid and coax inner and threw them in the kitchen bin.

Next task was soldering the centre pin. With 7mm coax like H7 this is tricky because the hole in the pin is narrower (or so it appears to me). Anyway I got it done though I dropped a little ball of solder onto the tip which I carefully filed off. So that is ready. All I need to do is slip on the insulating bush, put the barrel over the whole assemblage and tighten up the entire thing.

But there was no insulating bush.

Arrgghh!

It was here. I remember taking it out of the barrel and pulling the pin out right at the start. Is it on the cupboard I have placed all the bits on? No. Under the baragraph which is also on the cupboard? No. Behind the cupboard having slipped down the wall? Is it on the carpet? Under the radiator? Has it rolled into the shack or the bathroom? Did I take it into the shack? It is at the bottom of the pockets of my overalls? No to all these. 

Can I borrow a bush from another identical plug? There are no more identical plugs. There are ones that look the same but turn out to be PL-259s. There are others which look the same but turn out to be for 10mm coax and this is 7mm coax. Would the bush from one of those fit? No, but nice try. 

I went through my collection of plugs which I keep in jars in the shack. Ah, I found an M&P one for H7 which I could put on if I take all the parts of the M0MAT one off the coax and start again. But hold on, I would have to undo all my work so far. Anyway, that M&P plug is more expensive and I have been keeping it for outdoors use, and I would have to throw away the M0MAT plug which is ready but for the lost bush.

What a dilemma to have. My low budget project spiralling away because I might have to use a more expensive plug. £6.89 is at stake here. And I would have to throw an almost complete plug away. I refuse to spend more money on this (possibly doomed) project than I need to. In desperation I crawled around on the floor looking for that bush. It was not be found.

OK, I do have an M0MAT right angle plug for 7mm cable. It tried that and it turned out that it had all the same parts already on the coax, such as the washers and collar, fitted that plug. So I could fit that and get going and worry about the bush later (I had already spent a long time looking for it). That right angle plug is different in certain ways of course, as it has a fixed bush and also a fixed centre pin which is soldered to the coax centre conductor through a screwed in blanking cap.

I only had to unsolder the centre pin which I  had already soldered to the coax inner as of course the one in the right angle plug is fixed in place. That was the only thing I had to undo. As it happened there was just enough coax inner conductor to reach that fixed inner pin and I soldered it in and screwed up the plug. Perfect. It is indoors and so waterproofing is not important and the job is complete though the right angle plug looks as bit odd in that location attached to existing coax heading towards the shack.

I sat in the shack puzzled. How could I have lost that bush? Did I imagine that I had pulled it off the centre pin? Had someone sneaked in and stolen it?

Probably an hour later it dawned on me. Maybe I had thrown away the bush with the discarded bits of braid etc. I checked the kitchen and I could only see the discarded bits in the bottom of the bin. Then a further check revealed the bush stuck to the bottom of the used insulating tape. Ah ha!

As both the original plug and the right angle one use the same parts (apart from the pin and bush) I was able to take the bits left over and make up an almost unused plug, the only noticeable difference being that the centre pin had been soldered and then desoldered. It lives on for some future use. I did not need to undo all the earlier work nor add £6.89 to the project budget. Hooray!

The recovered bush and a right angle plug similar to the one later used

The message of all this is...

Never tidy anything up. 

73 Jim

GM4FVM

P.S. As a general rule I do not do much tidying up anyway. How did it happen that I let my standards slip and actually tidy up this time?

Six metre band - more than just "magic".

I wince every time I hear someone call the six metre band "the magic band". This is a scientific hobby, and magic means affected by supernatural forces (or supernatual beings!). I am pretty sure that the only things which affect the 50MHz band are natural forces.

Sorry to be a spoilsport, but using an incorrect term just infantalises our hobby. It is for us to try to understand the scientific way propagation works on all bands including this one. Just to kick the whole thing into the long grass but putting it down to magic risks radio amateurs looking stupid. Are we becoming lazy and not looking for the reasons why this wonderful band behaves the way it does? I doubt if governments who spend millions on attending conferences and lobbying to preserve amateur radio privileges would appreciate us throwing 50MHz propagation into the bin marked "magic".

Do I know the reason for specific openings on 6m? No, of course not, but I am willing to put a bit of thought into what I see happening.

On 5 October 2026 I was sitting at the radio hoping for an opening on 6m. I do not usually do that during October. I was warned in advance about this as I had seen on SolarHam that a coronal hole had spat charged particles into space and some was expected to come our way. On days when this is predicted I am hoping for a Kp number of about 3 or 4.

SolarHam update, 4 October 2026

Before this coronal hole effect reached Earth I was hearing nothing on 6m. The main opening in the UK happened on 5 October. By 6 October things had returned to normal and I was not able to have a QSO in the following days. But on 5 October I worked 24 DX stations in 16 squares in 9 countries. This was between 10:45 and 16:02, minus two hours for an international shopping jaunt to England.

6m contacts at GM4FVM on 5 October 2026 (Image ADIF to Karte)

Apart from two other days when solar activity was predicted when I worked a total of three stations, I have worked nothing on 50MHz outside the UK since 30 August. Nobody worked for 32 days of normal conditions, then 24 stations in a day, then back to nothing. Quite an opening. Magic? That would be a handy way of hiding it from any further investigation. I do not think the 5 October opening was due to magic.

These contacts were clearly "Sporadic E" (Es). They had the clear signs of Es such as considerable strength and they were all within about 2200km. Another Es characteristic was that the propagation moved around, first covering Italy and San Marino, then adding Spain and then after I returned from shopping, Eastern Europe with Italy still present. Best DX for me was 2027km to YU7EF in KN04KT

I saw no opening on 70MHz though there were a few contacts further south of me. I did see Es contacts on 28MHz at the same time covering similar parts of the world.

Most amateurs are probably familiar with Sporadic E. It happens every year during the summer and covers amateur bands from below 28MHz to 144MHz. During about four months in the summer each year we see Es happening regularly without watching for solar events. This year it was definitely over on 50MHz by the end of August. Summer Es does not happen in October. 

There is a widely accepted model for how Es works, and that explanation does not involve charged particles from the sun ...

Proposed Sporadic E explanation (retrieved from old FVM blog)

That explanation explains successfully why Es happens independently of the solar cycle - this process relies upon ionisation which takes place when meteors enter the atmosphere and are slowed by the atmosphere, providing all the energy required for ionisation. The arrival of large quantities of tiny "random" meteors happens all year and is fairly even in quantity (meteor showers by comparison provide only a small portion of this material for most of the year).

The general understanding of all this is that this "wind shear" explanation depends on seasonal factors. The seasons are driven by the Sun's heat so of course Es is so common during summer. Apart from the peak days of summer, it only happens during the local daytime.

So far so good. Under this explanation Summer Es does not depend on charged particles from the Sun thus does not depend on Solar Wind, the Solar Cycle or anything similar. Then what explains the 5 October 2026 opening, and others like it, which do seem to be related to solar activity? 

I can be fairly sure that something is going to happen during the winter when SolarHam predicts charged particles are streaming our way. What I cannot know is if the polarity of these particles is suitable to create an opening on 6m. Sometimes I strike lucky, and sometimes I get nothing. Sometimes the particles shoot past and miss the Earth. We cannot make more than an approximation of the speed of the particles as they leave the Sun, the size of the ejection, nor their complex angular velocity, so the predictions can be wrong. But I have seen enough of these events to be fairly certain that when Es happens during the winter months it is often related to solar activity, and I can be warned of that in advance by a raised K number predicted on SolarHam. 

The wind shear explanation has been professionally tested and I am sure that explains Summer Es. I might add that I am unsure if the wind shear explanation accounts for the sudden dramatic opening on 5 October and others like it, nor "Winter Es" (often wrongly called "Christmas Es"), nor the Europe-Japan openings in high summer, nor "Polar Es", nor "Auroral Es". In short, it seems to me that there may be more factors at play producing refraction in the E layer than just the wind shear theory. And I can be pretty sure that some openings that get put down as "Es" are definitely of an entirely different origin, such as long period ionisation which can happen during extremely strong meteor showers. I think it might have different causes, but it all looks like the same old "Sporadic E".

I wonder are there possibly several processes happening which are all lumped together by hams under one heading. Just because we amateurs see the characteristic Es type opening maybe we then categorise them all together as "Sporadic E". Sure, all the propagation happens in the E layer, has a maximum path on a single hop of about 2200km, it all moves around, covers small areas at the DX end, etc. However, that does not mean that they are all caused by the same mechanism.

Specifically, these winter openings seem to me to coincide with solar events. Can that be coincidence? I doubt it. I have followed this possible link for over ten years. One theory which has been suggested to me is that the arrival of charged particles into the E layer gives enough extra energy to cause ionisation and trigger Es. That sounds quite plausible, but does it happen by an entirely different mechanism to the wind shear theory? I personally cannot see that increased solar activity would influence the wind shear mechanism which would otherwise be asleep over the winter months.

So the conclusion is, I don't know. Still, I am not inclined to let this go without giving it some thought. When SolarHam predicts a coronal hole or a mass ejection during the winter months I will be ready on 6m. I cannot be certain though, as only a K number of about 3 or 4 is likely to work. If the stream misses us then the number will be too low, and if it is strong and hits Earth squarely the K number will be 5 or more and an aurora will strip out ionised particles and prevent any Es. Still, an aurora is good in other ways, and as it calms down you often get Auroral Es which is another benefit.

I cannot see how the wind shear theory explains a day like 5 October. I cannot see how it explains Winter Es and all that type of propagation either.

I can say something with a fair degree of certainly:- IT IS NOT MAGIC THAT DOES THIS. 

73 Jim (disappearing in a puff of magic ionised dust)

GM4FVM

Replacing a rotator at GM4FVM

In brief, I tilted over the mast, took off the Yaesu G-450 which I had been using, installed a new G-1000 model, screwed everything back together, raised the mast and after calibration and installing a new USB controller, everything worked. 

OR you can read the long winded version (or just look at the pictures) next:--- 

Here at GM4FVM we have two masts and thus two rotators. On the main mast is (was) a Yaesu G-450 rotator. 

At present on that mast are three antennas. First is the two band (two feed) DUAL four element on 50MHz and five element on 70MHz. Above that comes an 18 element I0JXX yagi for 432MHz and above that is an eight element I0JXX for 144MHz. Since I recently moved the 70cm antenna to a position between the other two antennas I have become a bit concerned that this may have added too much load for the G-450, especially in this windy area.

The G-450 looking tired

Another concern I had was that the G-450 actually comes from an unknown background. I bought it in a silent key sale along with various other things (like the IC-7100 which I still use daily). I had no plan to use it, thinking it might give up parts. However, when my own G-450 failed I just put up this one and gave it no more thought. I do not know how old it is, or what work it has been doing before I got it.

And finally, I wanted to get more accuracy when it comes to directing the antennas. The G-450 has been operated using a Hy-gain YRC-3 controller. This gives me antenna control from the computer screen, and allows automatic moon tracking and so forth. The Hy-gain controller is fine for use on the lower bands, but it was not really accurate enough for the narrow beam width of the 70cm antenna. It would do for terrestrial work, but for moon bounce it cannot reach the accuracy I need (or what I think I need).

I have had computer control for a long time, originally using a controller kit from EA4TX and a Yaesu G-600 rotator. That arrangement went back about 20 years and the G-450s and the Hy-gain controller arrived about ten years ago. In fact the G-450 had been a step backwards in specification compared to the old G-600 and recently I began to worry if the G-450 was no longer up to the job of turning more, larger, antennas I now have.

So I began to think of a new stronger rotator. In the end I decided on the Yaesu G-1000. Compared to the G-450 this offered 33% more braking torque, up to nearly 100% more turning torque (depending on rotation speed) and 100% more weight capacity. The K factor, the overall measure of load performance, is 130% greater and the wind loading is 120% greater than the G-450. Overall this looked like a sensible step up to take.

The G-450 alongside the G-1000

The G-1000 has a DC motor while my older G-450 uses an AC motor. Hy-gain YRC-3 is switchable between AC and DC so it would drive the G-1000, but I wanted to step up to more accurate positioning while retaining computer control. The G-1000 controller has a six pin DIN socket on the back which allows the use of a Yaesu outboard box to connect to a computer via a USB socket.

The snag with the Yaesu USB box is that it costs £400+. After looking at a couple of alternatives I chose an ERC-Duo USB box which is often available in the UK for about £120. As it was out of stock when I needed one I ordered one from Wimo in Germany. The ERC box would allow me to interface between the G-1000 controller and PST-Rotator running on my computer and allow me full control and tracking.

When a suitably still day arrived to change over the rotators I hatched a plan to replace them without taking the antennas off their supporting pole. This would be tricky, given the weight involved but I hoped to support the pole from underneath. This would take the pressure off the rotator when the mast was tilted over, and allow me to change over. In the event it worked well. It would have worked even better if I had managed to get every aspect of the plan correct.

Mast tilted with pole supported and G-450 uncoupled from the pole

Once I had got everything in the right place I could uncouple the G-450 and remove it. Then by undoing the bolts on the upper bearing I could move the pole up the rotator cage and leave enough room to get the G-1000 into the space.

Along with the rotator in the SK sale came a spare Yaesu rotator cable. This had been cut and mended in three places but has proved to be of much use down the years. I used it to test and calibrate the G-1000 in the shack before the day when the change over was to be done. Whilst the calibration might be slightly different with my normal cable it would be close enough. In fact it proved to be within about two degrees. What went wrong here was that I set the rotator to 110 degrees when I always set my antennas to 100 degrees. Good plan which worked in almost all ways save one silly mistake.

I was able to slot the new rotator into the gap and lower the pole into the top bracket. Then there was the tricky job of tightening the bolts on the rotator which Yaesu insist has to be done in strict order in quarter turns at a time. This is good advice as I have snapped alloy fitting before with these rotators. Do not over-tighten!

G-1000 installed

That done I could lower the pole with the rotator (and antennas!) attached, do up the bolts on the base and start re-aligning the bearing at the top of the rotator cage. I was aware that this bearing had become slightly out of kilter over the years and so it needed to be done anyway.

With all that complete there were still a few jobs to do. Yaesu recommend testing and I did this first using the Hi-gain controller and the spare cable. I took this out to the mast and did various tests ensuring the everything was rotating freely. This was done with the mast still tilted but with the support removed, which meant that the antennas could rotate through 360 degrees.

Next task was to do some final tests from the shack using the G-1000 controller. These proved that only minor calibration corrections were needed, but everything was 8 degrees off target. That was because I had set it up in advance at 110 degrees. My rule of thumb is that antenna booms parallel to the ground equals 100 degrees. Doh! But it would have been 2 degrees off on the other side anyway so that was not so much of a problem.

This time I did a careful job, checking the "parallel to the ground" theory with a spirit level. I set each antenna carefully and then raised the mast vertically. Outside job done.

Careful twiddling got the G-1000 controller spot on. The G-1000 controller is much more accurate in its alignment than the G-450 was as it allows five different settings to be juggled. Once this was working OK, it was time to align the ERC-Duo USB box.

ERC-Duo box with 50 pence piece for scale

In contrast with the big heavy Yaesu controller, the ERC-Duo box is tiny and draws its current from the USB cable. This is basically another controller which gives its instructions to the Yaesu controller. Thus it needs to be calibrated separately. It comes with a link to download and install a "Service tool" and a "Rotator Control" piece of software. I used the service tool to do the alignment and save the data onto the computer. I will not be using the rotator control as the ERC-Duo can take instructions from PST-Rotator.

Final result.

All done now. I managed quite easily to get the Yaesu controller and the ERC-Duo to agree on the bearings and for that to line up with my key points viewed from outside. That needed an eight degree correction, easily done by moving the Yaesu pointer and setting an eight degree offset on PST-Rotator. 

I find it more accurate to use this "parallel to the ground = 100 degrees" alignment than trying to find North - eccentric I know, but practical. Obviously this angle will be unique to every tilting mast, but once you have worked it out it will stay true. On my other mast it is 98 degrees so the original and extension walls of our house are not exactly parallel ....

The only slight issue just now is that when I transmit on 2m the pointer on PSTRotator moves about four degrees clockwise. Just the pointer, the antennas and the pointer on the G-1000 controller do not move. This is RF is getting into the ERC-Duo leads somewhere, and I am busy trying to solve that minor problem. 

The new rotator moves quietly and quite quickly - the rotation speed is variable. It certainly behaves much better than the G-450 ever did. I am happier that this can take the strain of those three antennas, even though I am already wondering if the 432MHz beam would not be better on the other mast !!!! 

But why, oh why, do Yaesu keep selling rotators with huge expensive mechanical pointers when a simple digital display would do just as well? And why do they charge £400+ for a USB box when all rotator controllers should have USB connections as standard. SPID rotators have their failings, but at least they have no moving parts to break down and they connect easily to a computer.

73 Jim

GM4FVM

The lazy man's way to update Icom clocks

Why do I bother to set up the clocks on Icom radios? Once the battery runs down, why not just leave them as they are? 

HINT:- Icom make a software app that does all this for me!

Well, this goes beyond just looking at the radio and telling the time. Updating the clock (and the calendar at the same time) puts a date stamp on everything you record onto the SD card. 

For instance it dates and times recordings of various tests recently with Pom, DG7AC. Pom responded to my request for Ionoscatter/Q65 tests and we did some for several days. During these tests I recorded what I was receiving using my IC-7300 and IC-9700. If the clock is correct then the timestamp on the recordings allows me to work out afterwards which recording relates to which test. Without that everything is recorded with the wrong date and time.

No doubt there are all sorts of DStar things which need the time set too, but I do not know what those are (of course). 

When the rigs arrive they come with factory fitted lithium batteries to hold the time and date in the memory. These batteries are soldered in and are located in a pretty inaccessible place.  Over a period of a couple of years these batteries become exhausted and the clocks revert to zero every time the radio is turned off and back on again.

I see one of radio supplier in the UK is offering to replace the battery with a battery holder for a standard CR2023 battery holder which is located in an easily reached location under the rig's covers. Inclusive of transport for the radio down to them this costs £125.00. That would be three radios for me (IC7300, 9700, 7100) at that price, £375. Downside, you still need to go in to change the battery and reset the time when it does run out and this is not an Icom approved alteration. Hmmm.

£375, that is more than I paid for a good HF transceiver [That was 50 years ago Jim] .

On the other hand, I could just install Icom's free ST-4003W software tool which sets the rig time to your computer's time whenever you want. Sure, you lose the setting every time you turn the radio off, but it is easy to set it when you start everything up each day.

So I downloaded the software tool which you can find here. The instructions are simple. If like me you use data modes like FT8 you already have the rigs linked up to USB sockets on your computer. This software tool works with Windows and a wide range of recent Icom radios.

My IC-7100 taking a little longer to update its calendar and clock

Once I had downloaded it and installed it I could update the IC-9700 and IC-7300 in seconds. The IC-7100 takes up to a minute while it "sets the seconds". For some reason I do not understand the IC-7100 then holds the date and time for several days.

GB3NGI beacon switching from JT4 to CW seen from GM4FVM - note the time

The file in this case is recorded on the SD card as 20260823_143100, giving you date and time information.

This blog does not seem to upload audio recordings but I would share these too if I can find a way to do it.

I simply saved three tabs to my taskbar, one named for each rig. Then I just click on them in turn and all three clocks set themselves. You cannot do this when data mode software is using the USB connection, but I do it first when I turn on the computer. Once the clock is updated the Icom software releases the USB link and you can start WSJT or whatever you use. If you only have one rig then this is even simpler, just pin that Icom shortcut to the task bar, or run it from the start screen.

So, you get a nice correct clock on your rig. It will show your local computer time, not UTC or something else, but that is easy for me to correct as I convert between local and UTC all the time. 

It is a fiddle to do every day when I start the rigs. For me the warm feeling of having saved £375 quickly deflects my mind from that problem.

EDIT: Thanks to Carlo, IU1KGS, for emailing me with "An even lazier approach to update Icom clocks".

Carlo points out that it is possible for the Icom IC-9700, among other modern Icom rigs, to directly update their clocks via an internet time server. It seems this is covered in the advanced manual. My own 9700 is not networked so I need to try this out before I comment further but this seems even  more straight forward. However, for my older IC-7100 and 7300 I will need to stick to the Icom software (though the IC-7300 Mark 2 is covered by this).  

I appreciate that news Carlo and I hope to be posting various things to do with the IC-9700 later. I also agree with your comment that using soldered batteries in radios is crazy when every PC maker can fit a button battery holder and get longer life with a CR-2032. So why are we short changed in this way? On the other hand, it gives us something to think about. 

73 Jim

GM4FVM 

23cm Aircraft Scatter - Beaming at aircraft rather than along a direct path and the benefits of Q65.

The basic concept of aircraft scatter (AS) is similar to that of radar. However, in the case of aircraft scatter we are generally relying on signals being scattered forwards to a distant receiving station, rather than back towards the originating station.

This posting is about a series of tests carried out to establish the best way of targeting the distant stations using narrow beamwidth 23cm antennas and which data (or other) mode to use for this purpose. It is an expanded and updated version of my article which appeared in the GMDX group's Digest (gmdx.org.uk).

As usual, click on images to enlarge them if necessary. 

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In practice radio amateurs can use AS on the VHF and UHF bands to achieve QSOs up to a distance of about 600km. The exact distance will depend on the frequency, the height of the aircraft and the curvature of the Earth. This range can be exceeded by tropo ducts, but these are fairly rare. In the absence of a duct aircraft scatter is the most reliable way of reaching stations in the 250-600km range. The larger (or “heavier”) the aircraft, the better chance you have.

I recently started a series of trials on 1296MHz with Gordon, GM4OAS. Our stations are broadly similar, with Gordon running 250W and two 36 element yagis. I have 150W and one 36 element yagi. The path is 257km in length which might make us think that a tropo contact in normal flat conditions would be possible, but the terrain here means this would not be easy. The path crosses close to Ben Nevis and many other Highland peaks in the Munro Tops category. It starts close to sea level at each end and reaches over 750m several times on the way.

The mountainous path from GM4FVM to GM4OAS makes UHF tropo contacts difficult (AirScout) 

Despite many attempts we have failed to make a tropo contact between us and we are certain that any signals between us rely on aircraft scatter. 

AirScout

Starting out on using AS the immediate problem is not knowing where the aircraft are, and thus not knowing when to call in the hope that an aircraft is passing between you and the station you wish to work. To solve this dilemma there are several sites on the internet offering maps of overflying aircraft using their transmissions on the 1090MHz band to capture the height, direction and speed of the aircraft plus a host of other details.

Many amateurs use AirScout software by DL2ALF. AirScout uses reception of the 1090MHz transmissions to produce a map showing the aircraft. It integrates this with the location details of the station which you wish to work. Thus, when you enter the station you wish to contact it adjusts continuously to present a diagram of the path involved, the terrain, and any aircraft along the path which are at the desired height. (See reference [1] for a comprehensive description of the technique and the software). I have been using Airscout for several years.

After several AS contacts, initially using a single 36el yagi at each end, Gordon achieved dramatically improved results by deviating his yagi direction away from the strict direct path between us and towards specific aircraft instead. This involved using an ability AirScout has to directly communicate with rotator control software.

Up to this point I had used AirScout in standalone mode, setting the beam direction to the distant station manually. It seemed to me to be impossible to follow a fast-moving aircraft with the narrow beamwidth of a microwave yagi. I was not aware that AirScout has the capacity to communicate with the antenna control software in my computer to allow tracking individual planes - planes which could potentially be some distance away from the direct path.

Aircraft Tracking
Tracking as a concept will be familiar to many VHF+ enthusiasts. Many of us use a similar set-up to automatically follow the Moon across the sky while attempting “moonbounce” QSOs. However, the idea of tracking individual aircraft was new to me. Obviously, tracking the plane makes more sense than pointing the antenna direct at the distant station. It is the plane which reflects the signal, and it should be the obvious target. However, planes travel more quickly across the sky than the Moon does! Gordon explained to me the steps I would need to take to set up aircraft tracking and after a few false starts I got it working. I had not known that I had to upgrade PST Rotator (Software for Antenna Rotators) to the VHF/UHF version first. See reference [2].

My rotator for the 23cm antenna is a SPID RAU. The control unit for this rotator either has a USB or a parallel socket (in my case, parallel) to allow connection to a computer. The software I use in the computer to drive the SPID is “PST Rotator”. When tracking is engaged PST Rotator looks for a dump file in AirScout which contains the latest instructions from AirScout to point in a particular direction. AirScout knows which plane to follow because the user identifies it by clicking on targets from amongst the options presented. 

AirScout turns the aircraft image red if it appears to be likely to cross the direct path – otherwise they are grey. In the past I only considered red targets, and only when they were near the direct path (Airscout also indicates when they are very close to the path). Once we started targeting specific aircraft we mostly selected images which are grey and not very close to the path, the opposite to what we did before.

Without having to consider how all this works via all the different interactions etc, I can now click on the image of a plane on the map, and the software continues to find out where it is and points the antenna towards it as it moves relative to me. Just to assure me that AirScout is keeping everything under control, it continuously shows a compass bearing towards the plane which it is following, and I can see the bearing changing regularly on the rotator controller too. I can also hear the SPID turning through the shack wall (!). Eventually the plane goes out of range and the tracking stops.

AirScout showing an aircraft North of the direct path to GM4OAS which was suitable with tracking. Note that none of the planes are near enough to the direct path to be coloured red and they would not have been considered candidates without tracking.

The result of changing from beaming along the direct path to tracking the aircraft was remarkable. QSOs were longer and signals stronger. We had three or four contacts for each plane, allowing repeated QSOs to check the outcome. 

It has to be said that this path to GM4OAS possibly favours this approach. On long paths, perhaps over 400km, the difference between the beam heading for a usable plane and the direct path will be smaller. For long paths planes in some directions would be below the radio horizon if far off the direct path.

While it was not easy to calculate the exact distance away from the direct path we were able to use, we estimated it as in the range of 25 to 40km. This brought many more planes into consideration. Once we were both using tracking, we had a series of near-continuous contacts over a period of two hours, selecting likely planes as they arrived on the screen.

Somewhat chaotic screenshot taken during the tests. Two aircraft following each other off path provided time for repeated QSOs. The two traces can be seen on the screen.

Why use tracking? 

It would of course be possible to estimate the position of the aircraft and simply point the beam manually in that direction. The plane could then be followed by dead reckoning using the map and constantly updating the rotator via the controller. This would require a lot of guesswork and antenna repositioning. As a halfway house, the on-screen compass bearing could be used to follow the plane whilst controlling the rotator by hand. However, as AirScout could do the whole thing automatically that seemed like the best way to proceed given that aircraft scatter contacts require full concentration on their own.

Compass shown on AirScout while tracking an aircraft

We used tracking not just because it takes all the hard work out of keeping the beam pointed at the aircraft (but it does that nicely). It also finds the correct angle far more accurately than would be possible chasing the plane manually. I do not yet have antenna elevation, but it would set that automatically too. And finally it solves the biggest problem - it can keep pace with the fast moving planes.

Which mode to use? 

For the tests we started by using FT8, which failed. We then switched to Q65 version 15B. Q65 is particularly good at handling Doppler shift created by the motion of the aircraft. A 15 second tx period is short enough to complete a QSO during brief flyovers. We did not just use Q65 because I like it (though I do like it). We then tested Q65 against FT8, FT4 and CW, using aircraft tracking. 

We became familiar with the plane passes which worked with Q65. Over a number of these passes FT8 was a failure.

Typical failure to make contact using FT8, with zero decodes reported at either end of the path. Note the exaggerated Doppler shift common to all these tests.

FT8 failed for several reasons. It is less sensitive than Q65 - its coding makes it less suitable for scatter use as it cannot deal with what Doppler there is - and its longer 30 second periods allows for twice as much Doppler shift in the first place. 

We then tried a comparison with FT4, hoping that its shorter period might help. However, FT4 is even less sensitive that FT8, so the benefits of the shorter period were largely lost. Still, over a period FT4 give roughly one decode for every five decodes using Q65 on comparable plane passes. 

This is not an ideal way to rank these three modes as it did not directly compare them at the same time but instead measured decodes per plane pass. However, with a fairly large sample size I think it gave a representative result. Broadly we found the FT8 did not work at all whilst FT4 worked to some extent but not as well as 15 second Q65. These results were what you would expect given that Q65 is designed for scatter propagation and FT8 and FT4 are not. 

As an experiment we also exchanged callsigns on CW.  Later we tried to complete a QSO on CW while using tracking and this was successful. The signals were quite strong so this should succeed but the effect of Doppler was rather off-putting. At some stages the Doppler shift meant that the CW station fell outside the receiver's CW filter as the QSO progressed. 

We did not try SSB, which is often used for AS contacts during contests. Whilst tracking increased the duration and strength of reception, it also increased the potential for Doppler shift. Whether this would cause problems for SSB contacts is something which needs to be investigated. It may be that at 432MHz, where the shift would be smaller, there could be useful gains to be had.

Doppler shifts of 400 to 700hz over four minutes were common and this is difficult to deal with in most modes except Q65 and similar protocols specifically designed for the purpose.

Summary
Tracking the aircraft rather than beaming at the distant station produced improved results in the tests. This can be done automatically, which was something I had not considered. It is a method which I will be keen to try more often in future. Provided AirScout can access a reliable feed of 1090MHz plane data (something which it sometimes fails to do) this approach seems to have merit.

Q65 seems to offer benefits over other data modes and CW.

Thanks to Gordon GM4OAS for guidance and encouragement with this experiment.

References: 
[1] http://airscout.eu/index.php. The latest issue of the AirScout Aircraft Scatter Prediction Manual may be downloaded from here: http://airscout.eu/downloads/AirScout_V1_4_0_0_EN.pdf
[2] Information about PstRotator – Software for Antenna Rotators may be found here: https://www.qsl.net/yo3dmu/index_Page346.htm 

Ionoscatter 2026

Ionoscatter ("ionospheric scatter") is forward scatter in the ionosphere. I often work stations on 2m from 800km out to about 1600km at around this time of year, but I reckon that ionoscatter has potential for use during much longer periods.

In the past ionoscatter was only thought useful for very high powered stations. Now with the benefit (?) of FT8 I find it useful at moderate power (200 to 400W) with an equally moderate antenna (9 elements) during June and July. With a more suitable data mode I suspect it would be useful for longer periods during the year.

Right, on now to this year's results so far:- 

144MHz Ionoscatter contacts at GM4FVM on 2 and 4 July 2026

Click to enlarge image etc. 

OK, so first issue:- this looks like the time of year and direction you might be working Sporadic E, so how can you be certain this is not Es?

Well, Ionoscatter (should we call it Is to distinguish it from Es?) is generally much weaker. Also, unlike Es it hangs around for ages and can last hours on an individual station. And thirdly it tends to occur only at this time of year (using FT8). So, in 2023 I heard it four times between 30 June and 12 July, in 2024 only once on 23 June, in 2025 not at all, and so far on two days in 2026, 2 and 4 July. Generally the times were between about 10:00 and about 13:00 but one as late as 14:39.

Left: a tropo signal (MM0CEZ), right ionoscatter (SM0LQB)

Ionoscater leaves a unique trace on the FT8 waterfall. It is often broken and patchy but stays at the same strength. Often you can see meteor scatter bursts which usually prevent the transmission from decoding. Using FT8 it can take a while to get the QSO finished. The key point is that although it is weak, the signal can been seen for long periods at fairly steady strength. The ultimate limit is FT8's ability to decode it because FT8 is not a very good mode for very weak signal work.

Second issue. You may ask what is the point of looking for this form of propagation when it is weak and only usable for a short time of year. Well, it seems to me that if we were unleashed from the limitations of FT8 it would allow decodes over long distances for much longer periods of the year. 

The mode I would suggest which I fancy would work better would be Q65. Much work was done by G4CDN and others using JT65 and QRA64, the modes which were available to them at the time (see  https://ei7gl.blogspot.com/search/label/Ionoscatter and please don't blame me if this link stops working - look it up instead). JT65 certainly works, but surely Q65 is much better suited to this type of work.

Ionoscatter is in fact working at the higher end of its frequency range at 144MHz. It is suggested that it works best at 35MHz and it should therefore be a good target for 50 and 70MHz experiments. And yet I rarely see European stations trying this. If I look at DXMaps I often see US and Canadian stations working to these sorts of distances using Q65, but I do not see that on this side of the Atlantic. Anyone interested? 

Some of you used to read my old blog, where I often lamented the use of FT8 on VHF/UHF. I feel sure that Q65 is far better suited to these frequencies. Well here I go again and I am not finished today. If you read the WSJT-X Users Guide you will see the uses Q65 can be put to. It even shows a Q65 Ionoscatter image. I'll print it below here because I suspect that very few amateurs ever read the guide, but instead use WSJT-X without really knowing what they are doing....

So for now I will continue to look for Ionoscatter on 2m for a few weeks each summer, mostly in the mornings. I know that it has far more potential, but if everybody insists on using FT8 then that is the only few weeks I can use it.

Any Q65 skeds from stations in the 800km to 1600km range welcome. 

73 Jim

 

 Below: From WSJT:X users guide (link to QSJT-X site is in the side bar of this blog)

12.4. Q65

Q65 is designed for fast-fading signals: EME, tropospheric scatter, rain scatter, ionospheric scatter, trans-equatorial propagation (TEP), and the like. The following screen shot shows the Wide Graph and decoded text windows after processing a Q65-60A sequence received via EME on 6 meters, by W7GJ Transmissions are decoded from N0TB, N8JX, W1VD, and VE1JF, all by the EME path.

The Q65 decoder takes advantage of a priori (AP) information such as the encoded forms of one’s own callsign and the message word CQ. In normal usage, as a QSO progresses AP information increases to include the callsign of the station being worked and perhaps his/her 4-digit grid locator. The decoder takes advantage of whatever AP information is currently available.

Here’s a similar screen shot for a 6 m ionospheric scatter signal over the 1155 km path from K9AN to K1JT, using submode Q65-30A. The received signal was barely audible most of the time.