4m/6m dual band antenna

Well, that great television detective Vera Stanhope arrived in Burnmouth and my antennas were not visible in the background.

Burnmouth harbour had become a salmon fishery base, and a body was found floating in the tide. With murder brought so near to GM4FVM, I have been wondering about my security. I am a bit more visible than I was thanks to a new antenna for 4m and 6m. Well, actually it is the same size as my previous antenna up there, though it has more elements on a single boom.

I was not a big fan of dual band antennas until Antennas and Amplifiers started making carefully designed yagis with separate feeds. This was based on my experience with my Vine 4m/6m yagi, which had 4 and 3 elements respectively and a single feed. I just did not like a single feed.

I had a system whereby during the summer I would have separate antennas, and during the winter when the winds tend to be higher I put up the old Vine again. Even last year when the 6m antenna was just a simple 1/2 wave vertical I stuck to this system. If I needed any proof of the wind force the 1/2 wave bent when I left it up over the winter. An earlier 4m vertical there did the same thing and ended up crooked.

The old Vine (left with Diamond vertical), and the bent 6m half wave (right)

So I thought a compromise was needed. Could I get an antenna on a single boom which did not require a single feed, but which was also able to survive the gales? Ideally this would have similar gain figures to the two separate 5 element beams for 4m and 6m I use during the summer. Maybe not all of this would be perfect but it would be better than what I do now.

This question was then put to Goran, YU1CF, at Antennas and Amplifiers and he went away and poured over his beam modelling software. Actually, he spent ages on it. My specification was for a 3 metre boom maximum boom length and with any benefit of the doubt to be given to the 4m band. Eventually he came up with a new design called PA5070-9-3-2CB. This has 4 elements on 6m and 5 on 4m, and the gain figures are much the same as each of my previous single band 5 element antennas.

Goran has managed to get it all into the same space as my previous 6m yagi - i.e. 3m x 3m. This is good news for the neighbours who will have to look at it. I definitely did not want to put up anything that was bigger than before. Of course it does have 9 elements, but that is instead of 10 elements on two 5 element beams. The biggest gain for the neighbours is that there is only one of these antennas instead of two. So, all round skyline effect is smaller. The effective length of the 4m beam is 2.2m and the 6m one is 2.8m. The elements are interlaced together lengthwise on opposite sides of the boom, just like the 2m/70cms one.

This arrangement leaves the other mast clear of 4m and 6m, so it just has two antennas, the 2m.70cms dual band and the 23cm yagi. There is a reduction in wind pressure all round. Also reduced is the overall antenna count as the 6m vertical has been taken down before it fell down and the 2m/70cms vertical has gone there instead. Well, I call it a 2m/70cms vertical, but it is really only a marine band antenna due to the death of FM activity round here.

Right so, let's see it.

Antennas and Amplifiers dual band beam, "2m/70cms" vertical on right

It is no larger in any dimension than the 6m single band antenna, so I am very pleased with that. We shall have to see how it performs. Now I have a 6m beam all year round, or at least I hope so. Goran's meticulous construction looks likely to be long lived.

My dislike of single feeds is silly. After all, all the elements in a yagi are parasitic except for the driven element. Despite that, and for no good reason, I do not like the sleeve arrangement.

So we will see.

73

Jim

GM4FVM

Japan on 2 metres, in easy steps

 Q. What does a man who likes following his summer sports (cycling, cricket), watch during the Winter?
A. Ski Sunday, of course.
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SPOILER ALERT

All will be revealed ....

==================================
 
Here is a photo of last night's sunset, which has little particular significance to this tale, apart from signalling high barometric pressure and possible tropospheric lift conditions

Sunset at GM4FVM on 19 January 2020.

Last Saturday (11th January) was interesting. Not that I set out to work Japan on 2 metres. It all happened in nine small steps.

Step 1 - The erratic linear amplifier

My 70cms TE Systems 4452G has never quite lived up to the performance of my other two TE Systems amps. Theoretically capable of 175 watts it has never really delivered more than 130, though those 130 have done very well for me. I set it up and left it on the "do something about this later" list, thinking it needed tuned like it's 6m sister.

TE Systems linear at GM4FVM, plus sequencer, fans, fan controller and rat's nest of wires

Over the past few days it had become erratic, cutting out. So something had to be done now. Funny how things get put in the "do something about this later" list and stay there until they appear in the "do something about it now" list becase they have failed entirely. So the "do something about this later" list is really a "do nothing and wait" list.

Wiggling various cables revealed an erratic connection in an "Anderson Powerpole" plug and socket in the lead. Being an inhabitant of the European side of the Atlantic, Anderson Powerpoles came as a surprise to me. I had dabbled in electronics for over 50 years and never seen one before this linear arrived. Of course I had heard of them, and I had read of the idea that they were the perfect solution to every need and they never fail. Try as I might I could not save these ones, and they were consigned to the bin.

Cut-off power poles and their boot.

I cut off the shrunk-on boot and I could not find a way to tighten the crimp on the plugs, so I had to cut them off. Then it dawned on me that the boot had been hot. Was the linear running low output due to power starvation?
=========================
I AM GETTING THERE

Patience ...

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Step 2 - Assuring the 70cms linear full power

As a bit of background I should say that this 70cms linear was bought from eBay second hand. It did seem rather cheap, and looking back in eBay records I discovered that the previous owner had bought it a few weeks earlier. This did not put me off, but it did make me wonder.

It had arrived with a few non-standard alterations. One was that it had an extended DC power lead, linked to the supplied power lead by the offending Anderson Powerpoles. The linear had Anderson Powerpoles fitted too and these were much heavier than the ones at the joint. I now noticed that the extension cable was a bit thinner than the original. So did the lighter extension cable and lower rated connectors combine to reduce the voltage, limit the current, and hence the power, to the linear?

Once I connected the shorter original power cable direct to the PSU I got 150W output. Not a bad improvement. So I got out the multimeter and checked the output of the PSU on its "13.8V" fixed setting. Hmmm, 12 volts. Turning it to adjustable voltage and resetting - 13.8V produced 180W output! Tah dah!

Step 3 - Testing the linear at full power

The TE Systems has four fans on top added by me. I am paranoid you know. Two run during PTT, and two on a temperature controlled switch, allowing me to monitor the temperature. This trends up to about 32C before stabilising. Would it get too hot on 180W and 13.8V, compared to 130W and 12V? Quick test, no sign of that, in fact it seems cooler on 13.8V (the fans run from a different supply so they were not turning faster).

As is so often the case I could find nobody on 70cms to test with. However, I noticed from PSK reporter that Colin GM0HBK was receiving DL7APV on moonbounce. Maybe conditions to the moon would be good and I could get a real test of the amplifier there.

Up on moonbounce DL7APV was POUNDING in. I did not wish to bother him as he was working a station in China and I worked him before ...

Step 4 - Turn 2m to moonbounce while I am busy on 70cms.

No point being in the shack and not having both parts of the dual band antenna working. If I am pointing at the moon I usually turn both bands on and listen. Why not? You never know. While I am on 432, I tend to set the 2m radio to 144.120. Theoretically, 120 is a sort of "calling frequency" but it is little used for that.

Step 5 - If I hear somebody on 2m, I should work them.

Whilst fiddling around between three stations on 70cms who were supposed to be operating (though I could only hear APV) I noticed that S51ZO was really strong on 144.120. I checked and I had never worked him, so why not give that a try?

Really strong in this context means -20dB, and I was something similar with him. I only have 7 elements and no elevation, so any contact is a good one. Mind you, the story goes that if you can get to the moon and back you can work anywhere in the world, as the distance is much the same. That never works for me, as on 2m I had only worked Europe. I did wonder a bit, because I have worked USA on 70cms EME.

Step 6 - Let stations know you will QSL.

It is customary to exchange confirmation of moonbounce contacts on the WSJT EME website
 https://www.chris.org/cgi-bin/jt65emeA
Well, I do anyway, and it seems to be expected. Joze, S51ZO was there and keen to confirm that I would QSL direct. I would, after all he was a new contact for me.
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 I AM NOT STRINGING THIS OUT

Nearly there

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Step 7 - If you post, you will be pounced on

I mean this in the nicest possible way - if you let people know you are on EME, they will ask you for skeds. And this time Juu, JH0BBE asked me to try to work him on 144.131.

Now I have had Juu ask me for a sked before and it did not work. Me? Work Asia on 2m?

Being a polite and civilised person, and a model radio amateur (as you all know), I would not refuse his request. Of course I will try,

Step 8 - If it can happen, someday it will.

On the face of it, given the lower power most Japanese stations run, there should be a chance of me working them on EME. When I see a US station I have a pretty good idea that they will be running 1000 or 1500W, and they need to be very strong for me to try my 300-ish watts. That is running my amplifier absolutely flat out, something I rarely do. But with Juu running 500W there was a chance.

Then he posted that he was hearing me. Eh? So I persisted. And then I decoded his call. Could this be happening? I sat there and watched, yes watched, the tell-tale double lines of the shorthand message RRR as it trailed down my waterfall. No need to decode it, I saw and heard it. Wow!

2m EME at GM4FVM 11 January 2020.

Step 9 - the QSL card

Juu asked for a direct card, which was off at the Post Office the next working day. And Juu's card arrived with me in just over a week. Three cards in fact.

It might be my first JA in EME, in fact my first station outside Europe on 2m EME, but it is first contact number 910 for him. He has 2m DXCC, and he has helped me to continent number 3.

My report from him was -26dB, effectively RST 0. He could not hear me, but the software could decode me. For me he was officially  -27dB, but I both saw and heard his RRR, so that must be RST 551. My noise level is very low.

Summary
I never set out to do that. I set out that day to fix the dodgy connection on the 70cms linear. I ended up working Japan on 2m.

There is a program on UK TV called "24 Hours in Police Custody". In it, real-life ne'er do wells, rapscallions and perps get questioned by the police while we all look on agog at the shocking nature of their crimes. The thing is --- it is real. They often say "I never meant it to happen. It started simple and then it all changed and got complicated. I was swept along on the tide of events.". Well, that is what happened to me.

Finale
The next day, peering again at 2m moon bounce, I saw this:-

200112_183900   144.120 Rx JT65   -25  2.5 1579 CQ S51ZO JN86                         f
200112_184000   144.120 Rx JT65   -27  2.7 1499 S51ZO ZL1HD RF82                      f
200112_184100   144.120 Rx JT65   -21  2.5 1580 ZL1HD S51ZO JN86 OOO                  f
200112_184200   144.120 Rx JT65   -21 -0.5 1501 RO
200112_184300   144.120 Rx JT65   -22  3.3 1582 RRR
200112_184400   144.120 Rx JT65   -22  3.6 1501 73
200112_184500   144.120 Rx JT65   -21  4.7 1583 73

That was both sides of an entire QSO between S71ZO and ZL1HD.

I have never heard a ZL before during my entire amateur radio career. And now I hear one via 2m moonbounce. What a square RF82 would be for me.

Sadly, I had left the rig running and it recorded that event. I could not try a QSO with ZL because I was not in the shack. I had gone to watch .... Ski Sunday.

73
Jim
GM4FVM

Lift conditions - at last

Dear all

After complaining about the superb tropo openings of 29 December missing me entirely, things got a bit better over the next ten days.

I should not feel hard-done-by any more, but of course I still do. Perhaps now I have less justification for feeling like that, but it won't stop me. I was born and raised in a section of society that felt that the world was against them, and I cannot shake that off just because it was never true. 

High pressure conditions brought some tropo on 1 January.

Contacts at GM4FVM on 144MHZ on 1 and 2 January2020.

I was pretty pleased with this, having missed out on the better opening a few days before. UT1FG/MM is an interesting contact as he chuggs around the North Sea. I can only work out his position when he gives a locator square while calling CQ on FT8. Sometimes he does and sometimes he doesn't. This time it was JO36, a square I do not often contact, it being entirely in the North Sea

I was even more pleased with the 70cms outcome

Contacts at GM4FVM on 432MHz on 1 and 2 January 2020.

Great to work Charly DF5VAE again, this time on 70cms for our fourth band. In fact I worked him twice on successive days. I am impressed by this performance given that I do not run high power on 70cms, have only a modest antenna, and I often go without contacts for days on that band.

Even more surprising was to work UT1FG/MM on 70cms. At first I was not clear what his locator square was - he might have moved since the 2m contact. As it turned out it was still the wet square JO36: I knew because he called CQ straight afterwards. It was a difficult QSO to complete - I am not sure what power or antennas he uses. But anyway I got it on the log book eventually.

Nice also to work DL7APV in JO62 again, and he provided the ODX for this event on 70cms, 1027km. By comparison on 2m, ODX was to SO3Z in JO82. At 1297km that hardly seems as much further than I might have expected. Mind you, on 70cms DL7APV has very large antennas.

For the two days, 70cm yielded 13 QSOs, 11 squares and 4 DXCC, while 2m accounted for 19 QSOs, 16 squares and 7 DXCC.

Quite possibly I was doing less well on 2m than I might have hoped because my LinearAmp Gemini 2 amplifier has been giving trouble. It was back with the makers for attention so for a while I was spending more time on 70cms than 2m. The resistors in the SWR protection circuit have been replaced. It is working again fine now, and I guess that is the problem solved. I have been pondering the possibility of upgrading the 2m linear but basically there is nothing wrong with this one.

After the 2m opening on 1 and 2 January, I turned my attention to the Quadrantid meteor shower and 6m. On 3 and 4 January I worked quite a few on 6m using MSK144 ...

Contacts at GM4FVM on 3 and 4 January 2020 on 50MHz meteor scatter.

A very nice set of contacts which proves how easy 6m meteor scatter really is. The stats bear this out, just 7 QSOs brought 7 squares and 5 DXCC. ODX was OH6WD in KP23 at 1756km.

By 5 January though the meteor scatter activity was declining, I could see those tell-tale signs that Winter Sporadic E (i.e. apparently "Es", but in the Winter) was back on the scene. You can tell when stations on meteor scatter have much longer reception periods than the usual ping on meteor scatter. This was the start of several days of Es, and when I eventually produced the map the data was so dense there was no room to add the callsigns.

Contacts at GM4FVM on 5 to 9 January 2020 on 6m Sporadic E.

On 5 January made just one Es contact, OZ5NJ, but on 6 January I made 14, reaching onto Italy, Sardinia, Spain, Switzerland, France and Romania. On 7 January I worked one station again (DL5WP), but on 8 January I worked 21, adding Slovenia, Poland, Croatia, Belgium and Austria. 9 January brought 8 QSOs adding Sweden, Estonia and Finland.

With the addition of a couple of tropo contacts that amounted to 45 QSOs with 35 squares and 18 DXCC. ODX was YO2LEA in KN06 at 1960km.

That was quite a spell. In my last posting I said that Winter Es keeps you on your toes because you never know when it will happen. Well here is the proof. There was no particular new ground broken, just a fascinating spell of operating over four days.

I heard nothing of Winter Es on 70MHz or 144MHz during these openings.

I suspect that is the end of Winter Es for this season for this season. Nobody really knows what causes it, though I do wonder about the fact that it occurs at the same time as peak Es conditions in the Southern Hemisphere. However, there is no known mechanism for that to work in the Northern Hemisphere, and the whole thing is a bit of a mystery. Still, all good fun.

From now until April I expect things to be a lot quieter. There may be a tropo opening. There may even be an aurora, the first in years. There may be more developments on HF as the sunspot cycle gradually starts to lift off. I doubt it though. I have plenty of projects to be getting on with. It was good though to have a good week's operating to fill my memory banks with material to keep me working.

73

Jim
GM4FVM