Biggest isn't necessarily best.

As usual, I have to say that just because I do not do some aspect of amateur radio, I am not suggesting that there is anything wrong with it. I do not do much with Summits on the Air, LF, home brew, contests, CW, Club Nets (any nets really), vintage equipment, direction finding contests, SHF ... probably means that I do not have the time. If you do them, well done. I admire the efforts of others in these fields, I am interested in hearing about them and reading articles, but I simply cannot spread myself thin enough to cover them all.

VHF operation and the associated antennas, and especially propagation are what interests me.

I have written before in this blog about where I think I fit into the broad spread of amateurs. Here is some of it ...

It seems to me that the amateur radio world is divided into three camps. Category A has those who have a simple set-up, a wire antenna with a "VHF co-linear" vertical and who shun any further development or learning. At the other end of the scale, Category C pursue their hobby with deep pockets, obsession and determination to out-punch the ionosphere and out-buy anyone who dares to challenge them. And in between is Category B, who are the ones who want to learn and progress beyond the simple, but who stop short of relentless pursuit endless contacts.
I know that I am in Category B, but I only know of two other amateurs in the world who think the way I do. So there are only three of us. Only three of us who cannot stick the mundane boring nature of aimless CQs by the unknowing Category As. And the same three of us have no need of "premium brand" radios, huge linears and towers turned from the bottom which the Category C folks think are essential. We just want to learn from our hobby. All three of us.

That comes from here http://gm4fvm.blogspot.com/2017/06/out-of-rat-race-bikes-and-update.html

Maybe there are more than 3 of us now.

I say again, it is not that I am against the way others get their radio thrills, I just prefer to do it differently.

I am driven back to thinking about this by the discussion recently about planning permission. Do I want/ need a better/ bigger/ higher antenna?

Does anyone? (Erm, that is for them to decide Jim).

Take the past two days on 4m.

70MHz stations worked at GM4FVM on 24 and 25 May 2019

This, by any standard, is pretty good. By the standard of my performance on the 4 metre band of 5 or 10 years ago it is fantastic. I saw several familiar callsigns being worked so I know several readers of this blog were in on the action too.

Was I happy? No. I couldn't work SV2DCD. I heard him, and checking with PSK reporter I could see that he heard me. We never heard each other's CQ, so no contact resulted.

WHY CAN I NOT WORK GREECE ON 4M WHEN I CAN ALMOST REACH IT?

70MHz band as shown on PSK reporter on 25 May 2019

I could see everybody doing remarkably well, but why couldn't I work SV2DCD? It must be that dual band antenna. I need a bigger/ higher antenna.

If I hadn't compromised by pairing up the 4m and 6m antennas for some test, I could have done it. I could have been a contender.

Those last two paragraphs are nonsense. This had nothing to do with my antenna and everything to do with my over enthusiasm (Don't you mean everything to do with your ego, Jim?).

I have done the sums and I know that I have as good a station as I can have. Sure I keep swapping about the antennas, but then that is what keeps me interested.

Here are the conclusions I came to ages ago...

1) Output power
As readability increases as a logarithm of power and not proportionately, there comes a point where adding more power becomes financially pointless. So many radios come with 100Watts, the legal UK limit is 400W, and 200W is a handy stopping point. 100W is fine, 200W is moderately affordable and has twice the result, but 400W costs rather a lot to do. The first 100W added to the rig adds double the result, but to double it again needs another 200W, and that is too far for me. Anyway, on 70MHz the power limit is 160W.

If you end up with lots more power than the weak DX station you are trying to work you will fail anyway - you won't be able to hear them.

2) Antenna size
This is not quite so simple, but nevertheless doubling the length of the antenna might bring about 3dB gain. The complication is the number of elements, which alter things in a complex way. It does not help that some manufacturers quote silly gain figures. Changing from the 3m boom 70MHz beam to the 2m boom 50/70MHz dual band beams might have lost me about 1dB on 70MHz. I don't really believe that 1dB was stopping me working SV2DCD.

I have done the sums.  A maximum 3m boom length is the best practical length for me - it fits my masts, it gives a good compromise of gain versus length and it does not look too dominating on the skyline.  I could still do a lot with 2m booms if I had to, and the difference would not be that great. I will probably go back to a 3m boom on 70MHz because I have one stored away, but a bigger antenna than that is just not worth it.

3) Antenna Height
I have a copy of the RSGB VHF/UHF Handbook which has a height gain chart. It shows "typical mast heights" between 25 and 50 feet and suggests that doubling antenna height between these limits will mean about difference of about 6dB gain. That certainly has not been my experience, and to be fair the book does say that a lot of different factor are at play.

My Tennamast, with the maximum height of just short of 8m and with mast and rotator above that, provides a top height of about 10m, where the 2m antenna is usually placed. I can raise it from about 6.5m up to 10m. The main factor I have found is that when it is lowered it is below the roof ridge line to the South, but raising by a metre or so clears this. At 10m it is above next door's roof line to the East. In the other directions there is no roof to clear. So far, clearing the roof line has been the only thing to produce a significant effect. Generally speaking I want it as high as I can when working DX, but it doesn't make much difference how much higher once the obstructions have been cleared.

My MM0CUG mast raises to about 12m at the antenna but as it is above the roof line at all times I never found much need to raise it. I have tried, but despite the figures in the book it makes little difference.

So my simple rule of thumb here is that I need to clear the obstructions, after that more height matters but not much. Sure, if I could go to double next door's roof line - 20m - I might get another 6dB as the book promises, but I would need a new mast, which would need to be much heavier and free standing, new planning permission, more money ... and it isn't worth it to me.

So why am I finding that more power, bigger and higher antennas don't matter to me?
This seems to run counter to logic. Surely a better antenna is always a better antenna? Isn't more power always better - didn't I read an article suggesting that every UK amateur has a duty to run 400W so that they do not take that away from us?

Erm ... no Sir, not for me. Of course better is better by definition, but then what about the cost? Am I really losing much by having what I have? I cannot see that I am. I cannot say what I am missing because I cannot hear them, but when I look at what others do with their better (more expensive) set-ups I think I can do without it.

Maybe I am trying to justify my own choice of mediocre performance but frankly bigger linears, bigger antennas and higher masts make no sense to me. I think this is because of the propagation types I work.

You only need to take a look at the maps of 4m activity over the last two days which are posted above. I could probably have done all that on a dipole. Years ago I used a dipole before graduating to an HB9CV which could do almost everything I needed. Sporadic E is generally high signal strength, you don't need a beam or a high antenna.

You could make a case for most of the propagation methods I use - Tropo Ducting, Sporadic E (single hop anyway), Aurora, Meteor Scatter and EME - have been perfectly successful from here without exceeding my self-imposed power, boom and height limits. In fact you could make a case that in many situations smaller, lower antennas are more successful for these modes. Smaller antennas have wider beam width, and lower antennas bring ground gain and may connect into ducts which higher antennas or sites might not.

The only exception to this general rule for Es is "multi-hop Sporadic E" where 1dB might make the difference (to SV2DVD?). There is still plenty of fun to have without those extra dB though - I worked Canada on 50MHz with 50W SSB and an HB9CV boom length 0.8m at a height of 7 metres. Maybe I would not have worked Brazil with that, but when I did I was still using the 200W/3m boom rule with 7m height in that case.


And that just leaves plain and simple tropo. "Inter G" working. For that task a bigger, higher antenna fed with more power would help. Great ... spend lots more money and in some situation I might be able to work the next county. I might be competitive in a contest. Sorry, not interested, give me propagation science any day.
===========================================
For the type of operation I do, I can see no point in going for the full power, max height big antenna set up. I know somebody with a high power super-station. On 144MHz he has a 4 yagi array with 7 elements each. I reckon he has 6dB more gain than I have, plus he lives on top of a hill. He is a nice guy and I admire what he does but that is not for me. He might be able to win contests and work more EME than me, but I reckon the price is too high. Not just the financial price, but also the planning issues, the neighbour relations and all the other aspects.

I am well aware that if it was not for super-stations with stacked arrays I might have very little DX to work. Their antennas do all the work for me. Yet I also do something for them. I am here to work them too. If it wasn't for my middle-ranking station they might have nobody to work. If we all waited until we could afford to set up a super-station there wouldn't be much activity.

So where does this leave me with SV2DCD?

I have already worked him on 4m. We had a contact on 18 June 2016 and exchanged QSL cards.

I think for a moment I got caught up in the frustration of it all. Who to blame? Must be the antenna, linear or mast. In reality, the propagation was probably against us. I have already worked out that bigger antennas are not for me.

Earlier that day I worked  E76C for a new country on 70MHz (we worked last year on 50MHz). So that was country number 41 on 4m. That means more than anything else that day, and I did it with my modest set-up.

There are still lots of things to do. I could probably do most of them with my old HB9CVs. Wimo sell a dual 4m/6m band Moxon, there are multi-band log periodics, 2m/70cms yagis, verticals and all sorts of other good small antennas. I believe that nobody should be put off by pictures in books and catalogues of vast towers and antennas which few UK councils would tolerate under the planning rules. I would suggest instead get something simple up to start with. Even a 1/4 wave vertical has infinitely more gain than if having no antenna at all is keeping you QRT.

Over 40+ years I have built up a few better-than-simple antennas and bits of gear. That should be fine for me. The cold-headed me is happy with it, but the hot-headed me gets frustrated and wants to fall for the myth peddled by the VHF books - that huge towers and antennas are necessary.

I am not in this hobby to bulldoze my way through. My joyous radio memories stem from surprising contacts made with less power and with smaller antennas than you might expect. I might lose sight of that and need to prove it all to myself over again (see above), but I count myself lucky to do as well as I do.

Now, if I change the dual band 4m/6m yagi for a 4m stored one in the garage, and divide the 2m/70cm dual beam into two antennas, then ....

Rest assured, I will jiggle it all, about but "200W max/3m boom max/10m height max" is still the rule.

73 

Jim
EDIT BELOW

2 minutes after I posted that ---

First SV on 4m this year, plus a new square ... and without changing anything.

Patience dear boy.

73 Jim

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

EDIT - now that I have an IC-9700, here is my first view of it ..
 http://gm4fvm.blogspot.com/2019/07/ic-9700-first-look.html
========================================================
EDIT - This posting has now been made redundant after 2 years waiting by the DX Shop PTT multiplier - see here.
========================================================

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

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

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

Here is how the IC-7100 does it (one output is called HSEND, and the other VSEND) ...

IC-7100 manual showing clearly how to set the two separate PTT outputs.

As usual, click the images to enlarge if necessary.

You select what you want in the settings ...

IC-7100 manual showing how to select the automatic PTT band switching.

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

IC-9700 "basic" manual showing just one PTT output.

Now, as I say, I don't have an IC-9700 so I cannot verify if they are indeed being supplied with the 7 pin socket. However, elsewhere in the manual there is an explanation of how to set the single PTT output to work on specific bands

IC-9700 "basic" manual showing how to set the single PTT output.

This is, of course, consistent with the wiring details shown in the other part of the basic manual. It appears from this that you can set the single PTT output to on or off on any specific band, any combination of bands, or none.

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

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

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

The IC-9100 manual showing how it should be done.

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

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

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

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

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

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

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

73

Jim

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

The equipment sale of a silent key amateur caused me doubts

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

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

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

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

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

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

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

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

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

Still, some good came of it.

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

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

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

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

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

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

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

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

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

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

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

73

Jim

GM4FVM

"Almost Sporadic E" and 6 metre band readiness

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

For the past ten days I have been decoding one-way FT8 signals on 50MHz which look like Sporadic E, and so have others. Sometimes I have called CQ and been heard all over the place ...

Stations reporting hearing GM4FVM on 50MHz, 7 April 2019, on PSK Reporter

All of this has produced just one QSO for me - SP4MPB on 4 April. The rest of the time I just see parts of signals being received. Even more frustratingly, I see myself being reported as heard be other stations, but I hear no replies. Collections of dots and lines which are almost enough to decode but not quite there, then maybe at a different time several decodes. Although I can receive them, none of the stations answer when I call. Lots of activity, even quite a few decodes at time, but only once a QSO.

Almost Sporadic E.

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

http://gm4fvm.blogspot.com/2017/09/8-sept-aurora-and-above-muf-propagation.html

"Above MUF propagation" is a fairly silly expression, but what it means is "above normal MUF propagation", in other words by using very sensitive protocols like FT8 we can decode signals we never noticed before.

Plenty of 6m activity on PSK Reporter, 9 April 2019, no QSOs though.

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

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

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

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

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

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

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

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

In the dire 1960s UK comedy TV series "Harry Worth", Harry used to open the show with a recording of himself reflected in a shop window .... no Jim, don't go back there again. Harry Worth's TV show should be forgotten but, yes, it did feature partial reflection in the titles. Yes, Harry was a bit of an amateur scientist. Anyway, partial reflection is a faint, shadowy event, and that seems to explain what I am hearing.

Harry Worth (the things we used to find funny) Photo Wikipedia (Fair Use).

Sure you can also explain these strange signals in other ways. For example, maybe the ionisation is rapidly variable and just reaching levels able to support refraction. I do not think so, as these signals are very weak (Es is very strong), and there is a one-way element. I can copy one or two or even three signals from station, but they do not hear me at all. At other times different stations hear me and I do not hear them.

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

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

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

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

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

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

73

Jim
GM4FVM
P.S. I have to post this now, as I have spent so much time drawing diagrams of one-way paths, small patches of ionisation, asymmetry ... grrr ... I am going MAD. Quantum theory, who needs it?

David Anderson, GM4JJJ, SK

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

GM4FVM with David GM4JJJ in August 2018 - photo taken by Pat

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

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

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

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

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

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

73's David

Jim
GM4FVM

More tropo, masthead pre-amps and sequencing.

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

Terrestrial television antenna at GM4FVM, with bandpassfilter and masthead pre-amp

I'll deal first with recent events before moving on to pre-amps etc.

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

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

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

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

Things kicked off on 2 metres on 22 February when I worked DL3TW at 13:57. It was slow to build up, but I worked DL6BF to round it off on 2 March. Even for a 28 day month it is unusual for an opening to last here from 22 of one month into the second day of the next month. To be fair, there was a tailing off followed by a brief ridge of high pressure at the start of March, but it still lasted a long time.

Pleasing as that was, 70cms was better in my view ...

Despite all the 2 metres business, 70cms produced several new squares, including JO23 for PE1PIX (my first Netherlands station on 70cms), IO65 for GI0OTC and JO53 for DK0HAT. Many of the contacts started out as 2m QSOs during which I was asked to move to 70cms, and once again I was asked several times to move to 23cms which I cannot do (yet). Very good.

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

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

Moving on ...

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

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

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

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

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

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

Simple masthead pre-amp arrangement for television reception

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

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

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

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

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

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

This should give you two elements in your system - one turns the power off to the pre-amp straight away, and the second delays any high-power reaching the pre-amp to begin with to allow time for the relays to work. In fact, either should work if the other does not. You might not think you need both, but you do. Or, at least, you will find that out for sure if you rely on either alone. Pre-amps are expensive, and you have to buy two if you blow the first one up.

2m and 70cms pre-amps on the mast at GM4FVM (I must shorten the 70cms cable)

My masthead pre-amp used on 2m has a rating for SSB of 350W on VOX (I can use 300W), but it can handle 750W when sequenced. I am not willing to risk 300W into it on VOX, especially as it it is rated at only 200W for FM, and my JT65 has a fairly high duty cycle. OK, so JT65 is not quite as demanding as FM, but moonbounce calls can be very long (as can meteor scatter ones). So this is where sequencing comes in for me.

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

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

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

2 step sequencing for an amateur station using a transceiver, linear and pre-amp

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

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

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

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

Most designs for home construction, and commercial sequencers, allow you to program various permutations up to about 4, so that you can tailor their actions to your individual needs.

The 4 step Down East Microwave sequencer with 50pence piece for scale

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

If you do not add a linear, or it does not include a sequencer as standard, you will have to incorporate a Bias-Tee to add the DC voltage to supply the pre-amp.

SSB Electronic Bias-Tee

Some radio manufacturers of VHF equipment include bias circuitry in their radios. The IC-910 had such a feature. I imagine that the forthcoming IC-9700 will also have this built-in. This would be very useful if the radio was to be used barefoot, with 100W on 2m and 75W on 70cms being fairly useful power levels.

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

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

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

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

73

Jim

GM4FVM

Good blogging and the data mode take-over (not)

I like a good blog. I enjoy reading the thoughts of somebody who cares about their hobby and shares their thoughts with us.

One I have mentioned before is Olli's, DH8BQA, here www.dh8bqa.de/. You can find a link to it on the right hand sidebar too.

Olli is very good at saying the right stuff. He is also direct and to the point, not like me who rambles. He posts occasionally, not too often as I do. He has interests in a mix of subjects from VHF to HF, which makes it interesting.. He does contesting, which I don't do. I find that interesting, and I even hope that Olli will do well in contests because he is "on my side" thanks to the blog. That way I can do contesting without actually doing the work.

We share enough interests to keep me looking at his blog from time to time. The shared interests extend to the 10m band, tropo on VHF and many other things.

Back in October Olli added an interesting coda to his posting about the conditions then https://www.dh8bqa.de/golden-october/. His remarks have been spinning around in my head, and I have been waiting to sort them out before posting something myself. Here is what he said about FT8 ...

While I see it’s advantages and therefor use it, too, I really hope it will not be FT8-only in the future because people are just too lazy and make it easy by just clicking around a bit on the computer screen (if at all and not automating things, automated QSOs are just machine to machine, this has nothing to do with amateur radio anymore). As long as it is just complementary I’m fine with it. If it ever turns to FT8-only (yes, there are signs of it ) I’ll certainly need to search for another hobby. And that’s from someone who is burning for our hobby … but let’s think positive.

I agree with Olli on this. I have given it a lot of thought over the months. I think my viewpoint on FT8 comes from someone who has been using data modes for several years. OK, I was using RTTY in the 1970s, but I do not mean that. PSK came afterwards and pretty well rendered RTTY obsolete (I am ignoring several other steps here).

When I really got into data modes, it was to do things which other modes could not do. That was:-
WSPR - low power propagation study
JT6 and FSK441 - meteor scatter
JT65 - moonbounce

Possibly because I have never trusted my morse code skills I turned to these data modes as a positive step to explore the potential of our hobby, not to replace SSB and FM.

It turned out that JT65 and JT9 were useful on 6m and 10m for fading long distance contacts, but that was a side issue. I never saw data modes taking over, and I hope they never do.

When MSK144 became available I stopped using JT6 and FSK because I found what Joe Taylor said was correct - MSK is better. When FT8 appeared I started using it instead of JT65 or JT9 on terrestrial stuff and now I keep JT65 for EME and beacons. Simple, I have not changed my methods other than updating the protocols as new ones come along.

Then recently I heard this mad howling from offended traditionalists. It turns out that they never noticed me on JT65 but now I am on FT8 I am a threat. Well, not me so much, but hoards of folk who think that HF = WSTJ-X = FT8 = data modes. NOT TRUE. WSJT-X is a resource of several protocols for various purposes, I have been using it since WSJT-X 1.3, and there has always been a lot more to it than one mode.

It turns out that newcomers are using FT8 in their droves, and this may or may not pose a threat to the world of amateur radio, or maybe the world in general. But how can I be part of that threat when I haven't changed? I have been using data for the majority of my contacts since 2010, so nothing new there.

So what is different is not that enthusiasts are using data modes for doing things that voice cannot do, but they are using it more widely - and getting further at the same time. And I can see the issue. When I tune to 80m or 40m the FT8 segments are totally overcrowded. There are signals everywhere, and most them seem to be doing exactly what can be done easily on voice modes. Of course, they are perfectly entitled to do that.

I say again, I agree with Olli. A fully FT8 world would would be terrible. I still use FM to talk to my pals, and I use SSB in contests. Sometimes I just use voice (because I want to). I find the mass use of FT8 on HF soul-less and rather pointless. Sure if I am in search of DX then FT8 offers advantages, but for QSOs round Europe on 40m? Even top band, that chat band par excellence, is full of signals relentlessly exchanging callsigns (is anyone home?). They would be better, in my view, changing over to WSPR and going to bed while leaving the rig on. If all you want to do is exchange callsigns you might as well give up.

I do WSPR and pour over the charts looking for patterns. I use FT8 on VHF probing the edge of the tropo or Es. But using FT8 just for local contacts? Come on! This hobby is supposed to be a challenge, or at the very least, an exchange of ideas. What personal growth can come from routine machine exchanges?

Am I saying that I am better than them, or that they should "do as I say, not what I do"? I do not think so. What I am saying is that I think a moon bounce QSO from here to North America, or one discovering winter Es on 6m, is more meaningful than 100 "Inter-G" data contacts on 80m. You can disagree with me if you wish, but I really cannot see the point of using a strict mode which limits your interaction in a general chat arena.

I bet this is fashion. Or at least I hope it is. I expect that a lot of people are just trying out FT8, and as they are only on 80m, then obviously FT8 is busy on 80m. I suspect that over time 80m FT8 will become the preserve of DXers and enthusiasts, and the bulk of the activity will move back to SSB or CW. If I was on 80m on a regular basis I bet I would have done the same. I do not blame FT8 for being popular, but I think that over time it will reach its own level (and mostly amongst the DX enthusiasts).

There are all sorts of doom-mongers around in this hobby. For example, they predict that digital voice modes and network radio are going to kill our hobby. To these people I say "nonsense". Our hobby has to be attractive to people, and if something else is more attractive then off they will go to those hobbies. We need to win them over, not blame them for making a logical choice. They said the same thing when VHF-only licences arrived in the 1960s. Then it was said that many people would go onto VHF and never bother "advancing" to HF licences. But I did. And today new entrants may well go into network radio, get a taste for communication, and see amateur radio as their next step. In the meantime, established amateurs are using network radio to support their needs, and attracting people over from there. Network radio can be the recruiting ground for amateur radio, just like CB was years ago.

Like those in the Navy, we in amateur radio are in "The Senior Service".

And, in my case, proud of it. Aye aye, Captain.

I think I have been moved to write this because a rather boisterous local told me that he had worked 500 stations on FT8, as if that required a medal or a certificate.We do not weigh our QSLs to see how many there are, we look at each one and judge its significance. One good QSO is better than a night full of clocking them off routinely on 80m. For me anyway.

I need a photo or the thumbnail of this post will look bare. Here is a photo of an IC-7100 with a nice new N-type socket added to the VHF side ...

... haven't we seen this before? No, because this is a second IC-7100. Do I need two IC-7100s? Probably not, but another one has appeared. Once it has proved that it works perfectly I may sell it on. It was in need of some TLC, new USB lead, firmware upgrades, and general tidying up. So far so good.

My FT-817 is seriously clunked. Its processor keeps locking up and while a reset brings it back, not for long. Unusually for me, the arrival of the second IC-7100 comes at the right time. The two things were not connected, but seem to fit together. Now, is the FT-817 worth fixing? The 7100 is vastly superior.

What does annoy me, still, is that the only place I can find an N-type panel socket with two holes is at Radioworld who charge £10 for them! Grrrr. I have plenty of 4-hole ones, but RS and eBay have none of the 2-hole ones. £10 for a socket. That is crazy.

D'oh. Am I ever likely to need another 2-hole N-type panel socket? No.

I said that the last time.

73

Jim

GM4FVM