Meet the Masts

I have various antennas here. My two tilt-over masts have been in position for many years and overall they have given good service.

The key thing for me is safety - they need to be strongly mounted and easy to work on. No ladders. Ideally they should be extendable masts meaning that they do not need to be on the skyline for any longer than necessary, with the added benefit that I can lower them out the strong winds we get here. I need to be able to tilt them to work safely.

While my antennas need to have enough elements to serve their purpose, I also need them to be reasonable size. I do not want them to be eyesores, and if they are too big they will suffer in our winds. They cannot be too heavy and over-stress the rotator, nor need excessive bracing. Everything needs to be made of materials which can resist the salt-laden atmosphere created by the nearby North Sea. Above the rotators I use thick wall 50mm diameter aluminium poles to support the yagis, and this also limits the overall size of the antennas.

Finally, I need to strike a balance in relation to the OFCOM regulations for radio amateurs in the UK. To manage enough output power yet stick to the rules needs a bit of thought about mast location. That thinking required me to have two supports as my first one would have been in the wrong place for my current 144 and 432MHz set-up. The OFCOM guidance suggests that if there is an issue with meeting the rules then just raise the antenna - great advice but not practical here. Thus it turns out that my 2m/70cm antenna has to be in the location now occupied by my second mast.

Fortunately it is easy for me to meet the regulations on 70MHz and 1296MHz using my initial mast so it remains in use for those bands. My 50MHz antenna does not fit on the original mast so it goes on the later one. Thus: two extendable and tiltable mast supports. It would be great to have everything on one, but then four antennas on that would become a bit of a nightmare.

The current pattern was not planned but emerged over the years. 

The Tennamast

My original 7.6m Tennamast arrived in 2008, 16 years ago at the time of writing. I quickly adapted it with worm gear winches. This means that both tilting and raising are very stable with no ratchets. I raise, lower and tilt the Tenna mast using a battery powered drill. Over the years all that has been needed is occasional greasing plus one set of lifting cables - more on the cable here.

Tennamast at GM4FVM with 36el 23cm and 5el 70MHz, 28MHz vertical alongside

Unfortunately although this location is great for any antenna at 70MHz and above, the longer elements of a 50MHz antenna would get caught in a building when the mast is tilted over. I had not factored this in when locating the Tennamast. While a 50MHz HB9CV type antenna would just fit, it needs to be side on when tilted, and then the longer booms of the 4m and 23cm antennas would hit the building instead. I bodged about for a while and then decided that the only answer for 6m was to locate that antenna further along the house on the gable end of our kitchen extension.

The CUG mast

The first antenna on the gable end was in 2011. I was quick to locate my 6m HB9CV there. Initially I used ladders to reach a set of T and K brackets fixed to the wall. Access got difficult as time went on and I bought a cheap scaffolding tower to make life easier. Despite this there were two "incidents" when I ended up in an uncontrolled descent and plummeted to the ground. In the end it was clear that I needed another tilt-over mast on the extension gable end to ensure safe access.

My CUG mast arrived in 2016, 8 years ago at the time of writing. On it went my 5el 6m PowAbeam and my 2m/70cm antennas.

The 10m aluminium CUG mast was installed by Gary and featured hand cranked winches. It pretty quickly proved to be too weak for the job in hand. As I have mentioned here before, it can get very windy on the East Coast of Scotland. The aluminium mast was simply too light for the stresses it was put under and I knew immediately that this was not my greatest decision. The choice had been made on the basis that an aluminium mast was about 20% cheaper than the steel equivalent. The Tennamst was steel and caused no problem, but I failed to learn that lesson. Aluminium might be a risk but it would probably be OK, or so I thought. That decision might have been a good one if I lived in an inland valley, whereas being not far inland from tall sea cliffs it proved to be not so good. Not that the aluminium mast would fail or anything, it just whipped and twisted about in the gusty winds. Maybe I had underestimated the wind loading of my antennas too.

I have learned over the years that if I make a mistake it is best to accept that and fix it. I contacted Gary and he offered me a part-exchange to trade up to a steel mast, the one I now have...

The steel CUG mast at GM4FVM, with DUAL 2m/70cm and 5el DUAL yagis and 4m vertical alongside

Changing over to the steel mast made a huge difference. The second mast is very stable in strong winds.

The steel mast came with a rotator cage, something which takes the strain off the rotator and reduces the possibility of rotator failure in strong winds. The inclusion of a rotator cage required me to purchase a Yaesu bearing which is fitted to the top of the cage, allowing the top pole to rotate.The winch is fairly noisy and I may have to come up with another winch solution similar to the one I used for the Tennamast.

Steel CUG mast at GM4FVM tilted over for some work on the preamplifiers

The steel mast is a three section version, whereas the aluminium one was just two section. When delivered the upper steel section kept sticking in the raised position leaving the mast unable to be lowered. Luckily GM3PPE came to the rescue with his large set of files, and some rogue galvanisation was filed off the upper box section. The three section mast now works well, but it possibly adds some scope for inaccuracy with antenna azimuth settings due to the extra slack in the two joints. This hardly matters in most cases, but maybe on 70cm moonbounce it might cause some problems.

While I had a issue early on with two broken pulleys on the original CUG mast, the second one has not caused any other problems once the sticking top section was filed down. Just because steel is heavier than aluminium the process of winching the mast over is now a heavy job.

I transferred the antennas from the aluminium mast to the new steel one. At the time these were, a 9el 144MHz and 16el 432MHz DUAL yagi fed separately by two runs of coax, and the 5el 50MHz PowAbeam. After giving eight years good service I recently replaced the PowAbeam with a 5el 50MHz DUAL. I stayed with five elements in order to keep the visual impact low but also to stay with a rigid boom and good wind resistance. While the steel mast could certainly take longer and heavier antennas, I do not want to go beyond self supporting ones into the world of bracing.

Winches

The Tennamast came with 600lb aluminium winches with ratchets which I replaced with worm gear ones, 1200lb for lifting and 1500lb for tilting. You can read about this here and see photos of the winches. One benefit of using a battery powered drill for lifting and lowering is that as I have three batteries for the drill I am unlikely to get stuck with a flat battery.

The first CUG mast used hand cranked winches which can be hard work. When it came to specifying a successor I opted for an electric winch. It is powered by a 12V lawnmower battery stored in a weatherproof "Dri-box" alongside. The battery can be charged in situ using a weatherproof mains socket nearby, or if it is raining or snowing I can carry the Dri-box into the garage and charge it there. It has to be charged every month or so, depending on use.

Noisy Rhino lifting winch at GM4FVM, with hand winch for tilting seen behind

The winch came with two remote controls and a wired rocker switch. The connections to the wired switch seemed a bit light for outdoor use so I took that off and simply use the remote controls. I only use them standing beside the winch, but even then the signal seems weak and sometimes is interrupted. The winch seems to handle the load easily. 

I fitted a fuse to the battery and used Knightsbridge weatherproof connectors to allow the battery to be removed from the winch circuit and charged. I then fitted a second Knightsbridge connector to a dedicated "smart fast charger". The charger can be used outdoors but it is not weatherproof, hence the need to charge the battery in the garage at times. A basic charge to 90% capacity takes 20 minutes, but for a full charge from empty can take about 40 minutes.

The Dri-box is intended for mains wiring for things like outdoor lighting. Here it only has a 12V battery inside and it seems to have remained watertight. I used heavy outdoor cable to connect to the winch as the current carried for short periods is quite high.

In conclusion

I certainly never set out to have two masts. However I am satisfied with how the present system works. It is surprising how often the two rotators are pointing in different directions. The load on each is reduced and so is the visual impact. Very rarely are both masts raised at the same time. Most of the time both masts are lowered - I would say that one of them is raised in daylight once per week or less. I am not so concerned about antenna height, it is the ability to tilt them for safe work which is most important for me.

The whole set-up meets the OFCOM rules. The masts have been up here for 8 and 16 years respectively with only minimal maintenance being required. Any maintenance which is needed can be done safely from ground level. Overall I would say I am content with the way the masts perform and I would recommend either of them to anybody who was considering something similar.

73 Jim

GM4FVM

New countries worked and DX records reached on aurora recently - thanks to Q65

I have posted before about me using Q65 for auroral propagation. If you need to, you can read about that here. However, this current post is about how much better I have been doing in more recent soar events.

There were two auroral openings here a few weeks ago (4 and 12 August) which I should perhaps have reported on at the time. Well, I had a rough posting in the works but it never got much further. 

Believe it or not I do have to lead a more or less "normal" life outside amateur radio. Sometimes I have to do things like replace 35 kitchen doors and drawer fronts using the skills I learned from "Squarehole". He was my woodwork teacher during our tempestuous time together back in 1968. Would it have helped if I had listened to him? Probably not. It might have helped if he had listened to me from time to time. There is only so far you can go with wooden tea pot stands when you future life is more diverse.

Ah well.

GM4PMK's magnetometer on 12 August 2024

As per usual, click to enlarge the images if necessary.

Anyway, those solar events produced contacts with countries which I have never reached by aurora before. Take for example OH6KTL on 144MHz, my first auroral contact with Finland on that band. I worked Lasse on both events. OK, I have worked Finland on 2m before, on meteor and ionoscatter, plus tropo, so what difference does it make using aurora? Simply that unless we know what propagation method we are using we will not learn anything about propagation. Remember I have this old fashioned idea that amateur radio should be about learning. Woodworking classes should also be about learning, even in 1968, but we will have to let that thought go. Not that I am bitter or anything.

At 1504km the OH6KTL contact is the best DX I have ever worked on 2m Aurora. Also on 4 August I worked OH2BYJ on 70MHz at 1571km, which was my best DX on aurora on that band too. The contact with OH2BYJ is in fact the best DX I have ever worked on aurora on any band.

An aurora almost a mystical event. Radio auroras produce the oddest conditions with roaring band noise, strong distorted signals and dramatic changes in conditions. If the polarity of the matter reaching the Earth reverses then the radio aurora can start or end abruptly. There is also the possible bonus of Auroral Es propagation at the end of an event, but this not so common. We may get two or three days warning of an aurora, or we may not. The feeling in the shack here is of witnessing a remarkable event. So the further I can reach during an aurora extends the majesty of the whole thing.

On 4 April I worked F1FPL on 2m for a new country on aurora. I had never even heard a French station from here on aurora on any band.

Auroral contacts at GM4FVM, all bands, 4 and 12 August 2024

It is not just 2m where I have been doing well. I have been working quite a few stations during 6m and 4m auroras. However, there is no doubt that 2m has shown the greatest benefit lately.

So what might have changed which makes for greater success? Obviously every event is different but over time I can average that out. I am doing better now. 

It appears to be largely down to my use of Q65. My hearing has never been good at picking out either SSB or CW during an aurora. As the distorting effect of the Doppler shift is worse for higher frequencies, that made me shy away from 2m during auroras. Q65 has lifted that barrier and allows me to spend time on 144MHz.

70MHz auroral contact with OH2BYJ on 4 August 2024

When it came to the contact with OH2BYJ on 4 August I could hear nothing but noise on the loudspeaker and see nothing on the waterfall. I could never have made this contact any other way simply because I could not hear him.

It is not just the removal of my hearing from the scene which helps. It is pretty clear to me that using Q65 is very effective. I am working further afield, reaching more stations and filling in some gaps. I recall receiving stations on SSB who were strong but I simply could not decode any modulation in them. Q65 seems to be able to reach those ones too.

In the past, auroral openings for me (especially on 2m) tended to be limited to within these islands with the occasional LA or OZ. Now the field is opening up for me to reach further. This can only be regarded as a victory for Joe Taylor and his team. I doubt if they had me in mind when they created Q65, but it certainly works for me.

Nothing that I say should be taken to suggest that we should not use CW or SSB during auroras. That is our choice. All I am saying is how effective Q65 has been for me. During the 12 August opening I was happy to work GI4SNA and GM4CXM on 70MHz SSB. Those were very pleasant contacts and let us keep that option open. However, they are examples of the shorter range contacts I used to make. SSB does not work well for me on 2m, and CW is doubly difficult for me on that band, and the distance I could work was always relatively short.

Maybe I am odd, but I have no problem tuning around looking for signals and switching mode as I think fit. I cannot see why some people see data modes as the road to extinction of our hobby - we are not obliged to use them. We can use data for some contacts and anything we like for others (and I do).

Q65 is very adaptable, and there are a range of settings you can pick. Most stations seem to be using Q65-30C during auroras. I have tried other permutations, but that one seems to work for me. I am still happy to work stations using another other variation, but I use 30C for calling CQ.

It seems that Q65 allows me to reach further, and for others in areas not often affected by auroral propagation it allows them to reach me. Over many years I had success on this amazing propagation method but it always seemed limited, especially above 50MHz. If Q65 opens the door to more contacts during auroras then I will be very happy.

I could go further and repeat my view from previous postings. I find that Q65 is better than FT8 for contacts in any situation on all VHF and UHF bands, right up to 1296MHz which is as far as I go. The higher the frequency, the better the outcome from using Q65. I cannot really see a reason why VHF+ operators continue to use FT8 when Q65 can produce more reliable, better, DX. I also cannot see why the RSGB have a 70cm FT8 contest when a 70cm Q65 contest would produce better results.

OK, maybe at 50MHz the benefits would be less apparent, but as we go up through the bands the disadvantage of using FT8 increases. An SP station was keen to work my on 70cm tropo recently, just as I was keen to work him (I have 99 squares on that band). It had not worked on FT8 so he suggested Q65. As it happened Q65 did not work either (it is not a miracle worker) but HE suggested it to ME. Come now, this is not just my hobby-horse now. It is time for us to face reality here.

73 Jim

GM4FVM

Is this the end of Summer, and Summer Es?

I tend to see the harvesting of the wheat field beside GM4FVM as bringing the end of Summer Es season.

That used to happen regularly early in September. However, last year it was a month early, and this year it happened on 18 August.

So I guess this is a silly romantic idea I have, as surely the 2024 Summer season can hardly end on 18 August?

Well the schools around here have gone back from their Summer Holidays - they reckon Summer 2024 is over.

In many ways I hope the 2024 Summer Es season does end now, because hopefully Autumn will be better.

The difference between 50MHz Es this year and the same time last year is pretty stark.

50MHz contacts at GM4FVM from 19 July to 18 August in 2023 and the same period in 2024

Only around 10% on the 2024 contacts were multiple hop DX ones (that equals two contacts) compared with 32% last year (36 contacts).

Things on 70MHz were similar. On 144MHz Es openings are unusual this far north so this is harder to judge on that band. There was one big single hop opening between those dates in 2024 on 2m, on 6 August, and just one small one in the same period 2023. If I could see any pattern in the 2m openings I would be very happy because they are rare as rare things.

What can explain the significant difference this year? Well it could just be down to the random nature of Es. You cannot count on Es at any time of year, and maybe this is just natural variation. 

On the other hand I have spoken to several people who are certain it is due to the sunspot cycle peak. I do not recall this happening at the last sunspot cycle peak but then everything was much less organised on 6m then. The season was much shorter and ended about now in the year in those days, but surely that was due to lack of activity. After all it did not resolve immediately outside the peak sunspot period. Anyway, this was discussed here and after reviewing the data I cannot say that anything remarkable pops up. I need to look more closely.

Perhaps because I have read in several texts that Es is not affected by the sunspot cycle (or not noticeably anyway) then I am reluctant to accept that it might be. The upside of the sunspot peak would be F-layer propagation which I have yet to see.

I doubt if harvesting the wheat really indicates much, but it feels like it does - and may be that is as good an predictor of Es propagation as the various websites which claim to know all about it.

Harvesting under way near GM4FVM, 18 August 2024

Whatever the cause, the effect is pretty clear. For a lot of the time (days on end) I have been looking at empty waterfalls and blank "band activity" lists. Thank goodness for aurora and meteor scatter.

Yes, they call it sporadic for a reason. So therefore it could recover tomorrow.

WELL, GET ON WITH IT.

73 Jim

GM4FVM

Tracking the path of Sporadic E openings

The paths of Sporadic Es (Es) openings can often be seen to move across the Earth in regular patterns.

At one extreme, at higher frequencies we regularly get openings which only include one or two stations, and there is no movement discernible there. At other times especially at lower frequencies there is so much activity from multiple areas of Es that we cannot make out any detail out at all.

From time to time I find an opening which shows up the movement in a clear way. I have described two of these before on this blog - 

1) here, where a 50MHz opening to Japan showed an east-west pattern at the Japan end and suggested that whatever propagation method opens this path it looks very much like Es at the Japan end.

2) here, where on 144MHz the distance of the path shortened 700km over a 22 minute period.

On 6 August 2023 there was a 144MHz Es opening which showed a definite east-west transit at GM4FVM.

As luck would have it, this was a good opening with me contacting 31 stations in 103 minutes. This covered 6 countries and 18 squares, with the best DX being IK7UXW in JN80 at 2236km. On the other hand luck also dictated that I was absent from the shack for 28 minutes roughly in the middle of the event, but this did not seem to make much difference. This time the average lengths of the paths changed very little but the azimuth angle moved steadily (roughly) from "south east" to "south south east". Overall the path traced by rotator was in an arc which headed from east to west.

I have dithered a bit over how to represent this on the blog. I have plotted graphically the azimuth (my beam direction) against the time and produced a line of best fit, but somehow the graph does not show how the Es shifted very well. 

So what I have done is to show the map of the contacts with a text box showing how the front of the contacts moved across, expressed in terms of time and azimuth. The azimuth (my rotator angle) is at the top, and the time that contact occurred is below. The azimuth figures were calculated from the locators of the stations I worked.

144MHz Es contacts at GM4FVM on 6 August 2024

You will probably need to click on this image to enlarge it to see the detail.

I have listed the contacts in two different colours - red for the first phase, blue for the second phase, and I was out of the shack in between.

The leading edge of the contacts moved from 122 degrees at 09:22 to 156 degrees at 10:33, that is 34 degrees in 71 minutes or almost half a degree every minute. In reality it was not evenly spread and at times (especially at the start and end of the event) it was moving more quickly.

The "searchlight" of Es propagation shining on the ground was tracing a path which moved past stations at a surprisingly fast rate. Generally as it moved on contact was lost with those behind, with only the odd contact in the rear of the leading edge.

During the period I was out of the shack it did not seem to move much at all. I must go back in the log and try to work out what was happening then.

It would be easy to dismiss this as an opening into Italy and France, with one contact each in Croatia, Switzerland (with a very determined 2E0 stations adding to the fun on tropo). Looking at my normal map of an opening it just looks random. However, looking at the timings the Es path seems to be moving in an organised way.

A more conventional view of the opening on 6 August 2024

When viewed in DX Maps it is possible sometimes to see areas of high frequency refraction which appear to move between squares in a westerly direction as the day progresses. I can see a similar effect in openings such as this. What the cause is could be difficult to determine. At first it looks likely that the Sun's movement relative to the Earth might be the cause. Certainly the Sun plays a part by driving the air movements which create and organise the Es layer. Ripples in the Es layer could also be a factor. However it might be more complex that that.

I wonder if this was one event or two separate ones. The fact that the propagation did not seem to move much during around half an hour when I was not in the shack might suggest that. Also, the full picture may be hidden due to the geography. Obviously there are not many stations in the Adriatic and Tyrrhenian seas. Signals from there might have given a fuller picture. Still it looks pretty clear to me that the paths were moving steadily westwards.

Here is the summary from that first map, still with the first phase in red and the second phase in blue:-

  156        151        148         144        140        139         136        131        122       Azimuth

10:59     10:44     10:42     10:35     10:00     09:41     09:36     09:31     09:22     Time

 More research necessary.

73 Jim

GM4FVM

I saw the propagation arrive from far away

I was out on my afternoon walk when I noticed a cloud formation which suggested enhanced propagation on VHF. It was a still sunny day on 31 July with some "nuisance" cloud towards the horizon. A careful look revealed a dark grey band below the distant cloud level. I recognised this as a band of still air above the North Sea, which indicates that a temperature inversion may be underway.

I put an inch to my step, hurrying down Ayton Law, past the alpacas sunning themselves in the still air, and home where I had a look at 2m and above.

Dark grey band just above the horizon, Ayton Law, 31 July 2024

Click to enlarge images if necessary, as per.

The dark grey band can form over the North Sea when pressure is high. When it comes ashore it produces the effect known in Scotland as the "haar". When warm air passes over the sea a foggy layer of condensation forms also known as a "sea fret". The large bank of air can be very still and stable, but the entire bank can sometimes extend ashore producing very strange conditions. When the haar arrives near GM4FVM it can be seen pouring over the headland to the south, spreading down the slopes and into the valley of the Eye Water in which this station is located.

On shore the haar produces a damp fog which feels wet and yet can be surprisingly cold for something produced below warm air. On 31 July when I approached home I also noticed a cold wind which often arrives at about the same time. This feels like the output from an air conditioner, and circulates around the stable air system. The Scots word haar is derived from a Dutch word for cold. Inside the fog it can be quite dark as if enveloped in cloud as in an aircraft, and with the Sun blocked out also strangely cold. A short distance away, outside the cloud, it will be sunny, still and warm. Overall these can be a remarkable effects.

A large bank of still air over the North Sea is just what is required for tropospheric propagation. The tropo predictions had not been too hopeful for that day, showing a detached patch of enhancement north of me and then some more over on the Denmark coast. Not promising as tropo requires a continuous path.

Hepburn Tropo Chart for 18:00 on 31 July 2024.

It seemed likely that a mass of air had formed over the North Sea and this was allowing propagation. The QSOs showed two distinct paths, one to the east to to SM and OZ, and one to the south east to DL and PA.

144MHz contacts at GM4FVM on 31 July 2024

Conditions on 144MHz have been pretty awful this year, reflecting the lack of these very conditions. So it was very agreeable to be able to work 15 stations across the North Sea, and the best DX to SM7KMJ in JO66 at 947km was pretty good.

On 70cm I worked across the North Sea to OZ2ND and PA3CWS both of whom I also worked on 2m. I saw nothing  on 23cm, despite trying hard.

Haar coming ashore is fairly rare round here. This time it did not arrive on shore, well not as far inland as GM4FVM anyway. However, seeing it in the distance and feeling that cold wind on an otherwise warm day put me on alert.

Now two days later the pressure has fallen and the usual strong winds associated with a weather system coming from the West have returned. There is no possibility of still enough air over the North Sea to hold a bank of air, and the warm weather has gone. VHF conditions have returned to their usual sleep. Even the alpacas are sheltering under the trees today.

Alpacas sheltering on Ayton Law, 2 August 2024.

Most propagation enhancements arrive silently and invisibly. Actually seeing one was a bit of a surprise.

73 Jim

GM4FVM

Meet the linears.

Being a VHF operator the big snag with linear amplifiers is that you generally need one for each band. You can get ones which cover two bands, but then you either have to use a compromise antenna or switch between the two. Also, I use three different rigs so there really is no help to be had there. I just have to accept that I need one for each band.

Therefore for those three radios covering five bands I have six linear amplifiers. Clear as mud?

Just to get this out of the way, I would rather have no linear amplifiers. Firstly I am not a fan of high power and I have always resisted running more than about 200W. This is just a personal bias. Anyway, I have found that I do fine with that sort of level. Secondly, I keep blowing them up. I can see why so many manufacturers shy away from building linear amplifiers. A lot of them are unreliable. Or is it me? Surely not.

I still resist running much power. In any case, there are all sorts of restrictions which would prevent me from doing it. The overall UK limit for 70MHz is 160W. With my present antennas at their current heights the OFCOM ERP rules limit me to 300W on 144 and 432MHz. 1296MHz is about to be affected by the new limits to prevent interference with commercial satellite systems, and for me this in practice means 150W. It is on this basis that I have set my limits for some time.

Recently OFCOM altered the rules for some bands but that did not affect the ones mentioned above. However, it did mean that I could run more power on 50MHz. Previously I had various linears for 6m, with power outputs of 100W then 350W then 500W, limited at the time to 400W. More recently I had been using 200W on 6m. When the limit went up to 1000W on 50MHz it began to dawn on me that I could loosen my corsets a bit. I dithered for quite a time before deciding to return to the days when I had a 500W potentially available on the one band I use where this is possible. Not that I use it all, but I could if I needed to.

50MHz - ACOM 500S

Acom 500S linear amplifier at GM4FVM

Although I could have gone for a much larger beast within the new limit, I decided that 500W maximum was a good target to aim for. I had good results at that level in the past. I decided on this one after having the loan of an ACOM 700. The 700 had 700W available which was more than I needed. Sadly it did not fit into the shack, but the 500 had the advantage of being much smaller and lighter. In addition the 500S also covers HF and 70MHz, should I ever need to use it there.

I was very impressed with the Acom 700. It worked with great ease, compared with the 500W Gemini which was my last 6m model with this sort of output. While the Gemini was screaming its head off and making the shack very hot, the Acom 700 quietly got on with its job. Happily, the Acom 500S has proved to be every bit as good. It has been here now for a couple of months and I am very pleased with it so far.

Immediately prior to using the Acom I was using my Gemini 4 on 6m. While the Gemini is rated at 300W, it could deliver only 200W on 6m. The extra power which the Acom can run is very helpful in adverse conditions.

70MHz - Gemini 4

Gemini 4 linear amplifier at GM4FVM beside its bandpass filter

I have had this Gemini 4 since 2016. In the meantime I have had three other Gemini amps for various bands but they have all gone now leaving just this one. Rated at 300W maximum, perhaps because it has mostly been run at just over 100W on 70MHz and for a short time at 200W on 6m, it has survived for a long time.

Unlike my other Geminis, this one is passably quiet. Loudest noise is the Tohatsu clunk when the relays engage. It does not have the "advanced cooling" of later Geminis, which also endears it to me. As it is under-run it keeps cool and works away without much attention. While it was away on 6m duty I missed the extra power on 4m, so I am glad that the arrival of the Acom has allowed me to bring the Gemini back to 4m.

144MHz - RM Italy LA-250

RM Italy LA-250 at GM4FVM

My previous Gemini 300W has gone for parts or repair, followed not long after by its replacement which was a Gemini 500W. My 2m linear is now an RM Italy LA250. Capable of 200W output, the RM is unusual in my 2m linear history in that it actually delivers what it claimed to be able to do. I installed it, it runs. It does not overheat, in fact it stays cool and does the job without fuss. There is a display which shows power out, SWR and temperature. The manual says that if the temperature goes too high the fans speed up - but they never have.

There are a few niggles. It is a very odd shape and it does not fit on any shelf I have without hanging over the edge. The relays sound like they are not high spec and it has PL-259 sockets rather than my preferred N-types. The output power meter really only works on continuous modes like data or FM, on SSB it shoots all over the place. None of this seems to get in the way of steady operation.

There is a cheaper version without the fitted fans which I thought about quite a lot. However, I might try meteor scatter or even EME with it so better cooling was required. So far it has never got warm to the touch.

This is my second LA-250. After the 300W Gemini had tried to incinerated itself (I think the fifth time that happened but I am not sure) I got fed up and bought an earlier LA250. I used that until I was moved to fix Gemini, which was about six months, and it never missed a beat. Then I sold it and regretted that ever since. So when I had a gap again the 200W LA-250 replaced the 500W Gemini and I have not yet noticed a difference in reports.

432MHz - Tajfun 1000

Tajfun 1000 linear amplifier at GM4FVM

The Tajfun has been here since 2020. I managed to blow a diode up thanks to a spike from my Icom IC-7100. I had excellent support from VH Electronics in Slovakia. Over the years the Tajfun has delivered what it was claimed to do. Rated at 500W for SSB and 300W for data, it runs this with ease. I use it almost exclusively for data. It has a turbine-like whine when under strain. Like the Acom and the RM it has proper advanced cooling.

The display covers PA voltage and current, forward and reverse power, SWR and it can be configured for various working conditions. The linear can also be set to run under contest conditions, which runs the fans continuously. 

At the moment I am having a problem with the display in that it sometimes freezes on transmit. I think I can fix that by reinstalling the software on the display memory card, which I must do soon. Not that it matters much, it still works fine.

The standard Tajfun 1000 runs 1000W with versions for 6m, 4m, 2m, or 70cm. The version I have is switchable between 2m and 70cms and only runs 500W maximum. On 2m it needs a bandpass filter (though I know one amateur who uses it on 2m without an additional filter). However, I almost always run it on 70cm.

1296MHz  - 2 x W6PQL homebrews.

 

150W W6PQL linear amplifier at GM4FVM

100W W6PQL linear amplifier at GM4FVM

My first 1296MHz linear was intended to raise the output power of 23cm to 100W. That linear was based on a W6PQL board and it came from Riccardo IK5CON, sadly now Silent Key. Although the Motorola XRF-286 should be capable of 100W output it only proved able to turning out 50W. That was a very useful improvement over the 10W produced by the Icom IC-9700. However, thanks to Sid G8SFA, I was offered a second amplifier also based on a W6PQL board. This amp has two devices but also failed to achieve the hoped for 150W output directly from the IC-9700 as it needed about 30W drive to achieve this. The answer was to produce a two-stage amplifier using the smaller one to drive the larger one.

The devices used on these boards require 28V DC and at first I used ex-LED light power supplies available second hand on e-Bay. When one of these failed I went instead for a new S-360-24 PSU which is rated at 360W at 24V. These generic PSUs offer good value but can have noisy fans. The ones with an S prefix usually have good protection against switch mode power supply noise and so far I have had no problems with this one.

W6PQL boards are in many of the home built 1296MHz linear amplifiers. My experience of them is that they are very effective and work well. The effect of the recent restrictions on 23cm output power appears to be that my output power of 150W is just about right for this band, though W6PQL offers boards with higher ratings and for various bands ... https://www.w6pql.com/600w+_33cm_amplifier.htm

Finally

I view linear amplifiers as an unavoidable necessity. Often they are unreliable so reliability is more important to me than having the highest power. Barefoot is generally not enough, but nor do I find the need to use a kilowatt. Being a VHF enthusiast I need one for each band, The solutions I have come up with work for me and at last seem to be settled for a while. Or so I hope.

73 Jim

GM4FVM

What a week

 In the last week I missed two 6m openings to Japan and one to the USA. Did that matter?

50MHz contacts at GM4FVM 9 to 15 July 2024

I will leave you to judge that for yourselves.

While I missed several openings, I was present for three fairly good major ones plus several smaller ones.

On 10 July I worked N4TB and later VE9HF in what seemed like "one-offs". Then at 16:15 the band opened and I worked four W stations in 6 minutes.

On 11 July the 6m band opened to the west at 13:52 and I worked 14 North American stations in 32 minutes.

On 12 July the propagation favoured the east in the morning with me contacting JR7VHZ and five others between 08:12 and 08:20.

On the morning of 13 July I was still looking eastwards and netted EX8MEM and UN8GEQ. EX8MEM was a new DXCC and at 5432km quite a nice catch. UN8GEQ is good DX too, and further at 5541km.

By the 14th I was back on evening duty and 6m obliged by opening at 16:29. I contacted 15 North American stations in 29 minutes before an enforced tea break. After tea I fitted in four more before deciding that the Tour de France highlights was more important than radio. Returning as late as 19:53 I reached KP4AJ, KP4SX, PU4DEE and PY2XB. PU4DEE was the best DX of the week at 9790km. 

What type of propagation was PU4DEE? No idea. Too far for multihop Es? Wrong time of year for TEP? F-layer? I am beginning to think that multihop Es can do a lot more than I used to believe.

There was still time to work JA7WSZ on the 15th.

Apart from all that superb activity most of the time nothing much was happening. There were long periods of blank screen. Patience is a virtue and all that stuff. The statistics on the Log Analyser are perhaps a bit misleading. I reckon that my time actually working stations was about three hours at most. Even then I missed three good openings. 

I am not one for being on the bands calling CQ all the time. If that works for others, fine, but my methods are different. I do not call CQ constantly but I do call often. My "Watchdog" on 6m is set for three minutes. That is the length of time my CQ might last, and often it is shorter. I seem to do OK despite what I must miss.

My success on 50MHz is something I could never have imagined ten years ago. I am not doing much different from then, my power is now not much more than before (remember the 500W Gemini amp, now long gone?). My antennas have been 5 element for years. I have been using the same radio for eight years. True, I changed the coax a few years ago, but for some with a slightly lower specification.

It cannot be what I am doing. It has to be conditions, which have been so good I can hardly believe it.

57 contacts (50 of those were beyond 3000km), 41 squares, 11 DXCC, and all in a week on VHF.

Enough of this. Time to get operating again before it all disappears.

73 Jim

GM4FVM