Be thankful for what you got

Can it be almost 50 years since I was first licensed? I sat my Radio Amateur Examination in 1974.

Ah, 1974. Simpler times. My revision notes consisted of one book someone gave me when I bought a receiver. And that was before they invented propagation, so no need to learn about that. But more on the days before propagation in a later post. Perhaps.

1974 had a warm Summer and "Be Thankful For What You Got" by William DeVaughn. What a great record for a hot Summer. Long and slow, with an insistent bass line and tight percussion. They don't make them like that any more.

"Keepin' up with Mr Jones? You don't need a loan!"

Despite William's advice I was later to borrow the money to buy an FT-101. Not exactly keeping up with Mr Jones, I told myself, just trying to hear and be heard.

Deary me. I still just want to hear and be heard. Yet, I get flustered when my station does not seem to be performing. I seem to have forgotten Billy's mantra about not to pushing on. I should be more thankful for what I have.

I also get frustrated about propagation which seems to have become "a thing" in the intervening five decades.

And so I was complaining about 6m propagation on this blog as recently as 9 days ago here

"That gap into North America looks very glaring"

but I also said 

"I have in the past worked in that direction into mid-August. There is still a chance."

Does complaining work?

Next day there was an opening and I worked 18 stations in the US and Canada over the space of 50 minutes starting at 13:09. I then had to wait four days until the next opening at 12:10 when in 26 minutes I worked 22 stations across the Atlantic. And two days after that I found the band open at 21:07 when I worked 9 stations in 23 minutes, and the activity only stopped when I realised that I was falling asleep.

US and Canadian stations worked on 50MHz at GM4FVM from 24 to 30 July 2023.

Total opening time was 99 minutes for 49 stations, which on FT8 means being pretty busy. All three openings met my standard for a pile-up, in other words I was not calling CQ but people were calling me and a queue formed to work me.

Perhaps I should complain less and be thankful for what I have got.

I heard somewhere that patience is a virtue. Maybe I should become more virtuous. 

Not so sure about that one. 

"Be Thankful For What You Got" sleeve. Image: Wikemedia Commons

73 

Jim GM4FVM

Honey, I blew up the linear amplifier

Well, the linear amplifier blew up, but it seems it was not necessarily my fault. Nor was it the fault of the linear.

This took months to resolve so this is a long posting.

Of course, I have a long history of blowing up linear amplifiers, going back almost 50 years. I trust linears less than any piece of equipment I have. They are almost always about to let me down. Having said that, this posting is NOT about a linear letting me down. It is about me trusting a radio to transmit a low power output, and me taking too many risks by assuming that it would behave itself.

I have tried to write this piece several times, but it looks as if I am blaming the linear, which I am not. I will keep going on about that, just as I go on about lots of things in this blog.

Icom IC-7100 "It was him what done it, Constable".

There is a risk using modern high gain solid state amplifier devices in amateur service. Due to the enormous gain available the danger is that it will prove impossible to reliably restrict the RF power supplied to the device. The attenuator built in to the linear has to be set at a level compatible with the radio, and thought has to be given to the possibility of a sudden RF spike over-driving the device and its supporting circuitry.

So the spike in this case was generated by the Icom IC-7100 (or possibly the computer too) and that caused damage to the linear. Multiple spikes over a long period, or so it seems. How could I let this happen? Well one factor is that the IC-7100 has been operating into other linears with higher value attenuators for years. These larger attenuators make the chances of overdrive are much less. As a result I had become lulled into thinking this was not a big issue.

I have been thinking about this type of thing for a long time. The same problem arises with transverters as I explained here back in 2019. In fact I was extremely careful with transverters and even then I managed to over-drive the attenuator in one of them, though in that case without any calamitous results. It seems as if I failed to learn that lesson.

When it comes to VHF and above the amplifier has the RF power on hand to destroy any masthead preamp or other device further along the chain, and that also has to be factored into the equation.

Despite all the knowledge I had, I still managed to over-drive my linear despite having set the "RF Power" control to the correct level. The simple cause was that I had relied on the ALC operated "RF Power" control to keep the drive power low at all times.

If the RF driver relies on using the ALC circuitry to limit the output power, the chances of a random power spike are quite high. Connecting this transmitter to a computer which has its audio turned down and expecting that level to be uniform is another risk in the chain of potential for over driving the later stages.

At this point I can hear a voice over my shoulder saying that valve linears are much more reliable. You know who you are. Well, maybe. Not necessarily if you take care and if your linear is carefully designed, as this one was. I have three solid state linears which have given more than five years trouble-free service. And some that didn't.

So here I am talking about my Tajfun 1000 500W 2m/70cm linear. I do not think that it was in any way at fault in what happened. Neither was the excellent SHF-Electronik MMV 432-VOX masthead preamplifier which went arrrggghh at the same time. Nope, it looks like RF spikes from the rig that caused the problem.

I have to say that both the suppliers, VH Electronics for the linear and SHF-Electronik for the preamp, could not have been more helpful in fixing the consequences. Aside from the postage, the charge was €70 for the linear and €7 for the preamp. From this you can conclude that it was not the main RF device which failed in the linear but simply one diode.

Tajfun 1000, the victim of the problem, not a problem itself

This is not a review of the Tajfun, a linear amplifier which I think pretty highly of. It is very difficult to photograph as it is glossy black on the front and the display panel is pretty bright so it presents me with a technical problem when it comes to making an image of it.

Anyway, moving on to fixing things, ...

The fault showed up when suddenly the Tajfun lost output power and the preamp suddenly had more gain when it was out of circuit than when it was in circuit. Something had happened.

At this stage Vlado at VH Electronics, who had supplied the amplifier, went to great lengths to try to diagnose the problem and fix it. Thanks to the nature of the design, a lot of things could be fixed and indeed updated over the internet. The software for the display was sent to me and I was able to re-load it on a new SD card, and then the same was done for the firmware for the control board. These things helped but did not solve the underlying problem. After eliminating the relays and cabling, the overdrive had caused a fault which had to be in the amplifier RF stage.

Another clever thing that Vlado was able to do was to interrogate the records of overdrive and power output warnings which are stored in the control system. From this we discovered that the Tajfun had (successfully) coped with a series of huge overdrive situations. The output produced by the linear was at least 10dB above the power settings I had used and 3dB more than the full peak power the linear was rated at. Running any linear at twice its rated power is asking for trouble.

In each case the Tajfun protection circuit had cut out as it should have done. However, it was clear to me that this was not me deliberately operating at these ridiculously high power levels but probably something which was momentary. I was setting things up for 200W output so it was not that which was the root cause of the trouble.

The control circuits cannot generate more power than the transmitter can produce so the basic fault had to be in the transmitter. I will deal with that later.

For now I need to say that once he had eliminated all the other possible causes Vlado asked me to send the Tajfun back, which I did. The Freescale device had survived running at twice rated power, and the power supply had coped with supplying the necessary extra amps. Obviously, this overdrive was indeed  momentary. Vlado quickly identified a diode in the bias circuitry and the linear issue was fixed.

ITB RF board inside the Tajfun 1000.

The Freescale MRFE6VP5600H device is in the centre of the photo under the alloy plate, firmly screwed down. At the time of this photo I had tagged on a direct co-ax feed at the bottom of the board, bypassing the relays to check that they were not at fault. This also bypassed the attenuator which can just be seen below the red wire, bolted to the bottom of the RF enclosure.

Early in our search for the fault Vlado had considered that the attenuator could be at the root of the issue. While he had the machine with him he wisely changed the attenuator for the most recent version, increasing the power reduction from 5dB to 6dB. We could find no evidence that the attenuator was at fault, and anyway it seems to me that it would be unlikely that it would fail momentarily, and then recover, several times.

I have nothing but praise for the Tajfun. Having been all round the inside of it I can say that it is carefully designed and well made.

So the Tajfun returned and quickly resumed producing the power I was looking for.

You cannot overdrive any linear, not even a good one.

Siggi at SHF-Electronik quickly repaired the preamp which had been driven with 6dB more than it was rated for. Once again, not the preamp's fault. The service offered by Siggi remains exemplary. It took me a while to get around to dealing with the preamp, and in the meantime I had replaced it. He fixed it and returned it very quickly, and now I have two 432MHz preamps.

Even I cannot use two 70cm preamps. 

I need to thank Richard GI4DOH for helping with the logistics of getting the linear repaired by Vlado. I will not go into the details, but Richard was key to resolving the whole thing.

The fundamental problem was my Icom IC-7100. Well, that conclusion is inescapable. This was the source of the RF drive which blew both devices. I have had spike problems before. I had grown complacent.

I had connected the IC-7100, capable of delivering 35W on 432MHz, and set the output power to 4W as that was what the linear needed. The possibility of the rig delivering a sudden +10dB spike may sound improbable, but actually the full rated input of the linear at 500W peak would have required just 10W to achieve. Anything over 10W would have pushed it too far. The evidence would suggest that it reached 20W at least.

So what to do next? I do not want to have fixed the Tajfun and preamp just to overdrive them again. 

I could have replaced the internal attenuator in the Tajfun with one of a higher value. That is the solution adopted in my Gemini linears which are set for 25W drive. However, I was reluctant to raise the value of the attenuator too much as the heat dissipated has to go somewhere and the linear generates as much heat as we might expect already. Also, what if that single attenuator fails?

In the end I decided to add a second attenuator in the tx line. The idea was that I could change the value if necessary, and move it outside the linear for cooling if that was needed too. Doing a few sums, it looked as if a 5dB attenuator would involve the drive increasing from about 4W to about 12W for 200W output, and leave 8W to be added to the heat inside the Tajfun. The Tajfun has efficient temperature controlled turbo type fans. This means that any spike would be reduced by 5dB, and the result would not over-drive the linear or the preamp.

Additional attenuator which is now fitted inside the Tajfun 1000

Then I have considered other ways of avoiding the spike in the first place. The big problem here seems to have been me relying on the ALC to limit the power into the amplifier. One of the points made at the launch of the IC-9700 suggested that it has a "true power limiter". This appears to be the "TX PWR LIMIT" control. It is in addition to the "RF POWER" control which seems to be a standard ALC-type limiter. I say "appears" as this is not clear in the manual which states "The Transmit Power Limit function limits the output power to the preset level for each band.".

Anyway, the worry I have with this is that if anything did go wrong with this (for example if I messed up the settings) the IC-9700 can deliver 75W into the linear as opposed to the 7100s max of 35W. And, yes, I can get settings wrong.

I am guided by the idea that if something can go wrong, it will go wrong. Years of being steeped in statistics and probability have taught me the validity of that old saying. However, I can also get too carried away. It is not very likely to go wrong. Adding 5dB attenuation to the linear still gives some protection. If I remain worried I can increase the second attenuator and help cooling by placing it outside the amplifier casing.

In any case, I am losing confidence in the IC-7100. The years roll on and new better designs appear. It now looks pretty dated as a superhet radio in a shack full of SDRs.

73 

Jim GM4FVM

50MHz so far in 2023 = good and bad.

I have just had a good morning on 50MHz. That was after a few weeks of sitting here every morning from 05:00 to 11:00 listening and, once or twice, calling. So if I had done this post yesterday the bad would have outweighed the good.

Let us get the bad out of the way first. Hours and hours each morning, day after day, spent hearing nothing. 2023 so far has not been great in the usual sense. There have been no openings for me to US or Canada. And until today, none to Japan. It took ages for the season to get underway.

I began to think that it was already too late to work Japan as the latest I have worked it previously was 7 July.

This morning (at last!) there was a good opening into Japan and I worked 16 JA stations and 5 in South Korea (DS/HL). That all happened in 94 minutes of heavy action before I had to do other things. South Korea was a new country for me on 6m.

Does 94 minutes to work a new DXCC justify all those hours put in over the past couple of months trying to work Asia? Yes, but I cannot deny it has been frustrating.

During all that waiting the question was - is my station deficient? Recently I have been watching other stations within a few hundred km of here working JA almost every day when I could hardly hear them. On close examination these other stations had antennas with about 3dB gain over mine and some more antenna height. However, that did not explain that they could hear these stations 20dB stronger than I did. 

Now that I have worked a few stations in Japan and Korea I can forget about my worries until the next time it matters.

So what have I worked in 2023? More DXCC than ever before - 73 countries. That has brought my all time total on 6m to 96. That sounds pretty good, though it took a lot of effort to do it. Who said it would be easy?

50MHz contacts over 1500km at GM4FVM 1 January to 23 July 2023

The image above looks a lot better today than it would have done yesterday. At last I am getting as far East as I had done South West and South. The relatively few contacts into Africa have been very pleasing for me. That gap into North America looks very glaring, but I have in the past worked in that direction into mid-August. There is still a chance. There is also scope into the Caribbean where Curacao and Bonaire were nice recent captures. There is a lot of work still to do into South America too.

So, of course this 2023 so far map is amazing. Could I have done better? I think so.

Improve my station. Get better at operation. Know when to be active. Marginal gains.

And so it goes on.

73 Jim

The hunted and the hunter on Sporadic E

It is not often I get on the receiving end of a pile up on the two metre band.

Yesterday it happened thanks to a long Sporadic E opening. When I see strong signals on 50MHz, about +7dB or more, I often start watching in that direction on 70MHz and 144MHz. In this case the 6m signals were coming from Italy which does not have access to the 4m band at the moment, so it was 2m which first saw results here.

Between 15:44 and 16:56 I worked 16 stations in 8 squares in Italy on 2m. Well not quite all in Italy.

144MHz stations worked at GM4FVM on 9 July 2023

As usual, click to enlarge the image if you wish.

The question might arise as to why I would want to work all 16? Isn't one enough to prove that the propagation is there?

Well, first reason is vanity. It is very nice to have an hour long pile up on me after I call CQ. Loads of stations want to work me. Clearly my station is superior as all these seasoned amateurs suddenly want to work me. But we knew my station was superior before this opening [steady on, Jim Bighead].

Second, real reason number 1, it was amazing to watch the propagation move around the map. Sporadic E on 144MHz is very selective (localised) and only a maximum of three stations were calling me at any time, not all 16. I enjoy watching this appearance of Es jumping about. I tried to draw up a diagram of this for the blog but it just did my head in. It was hopping about too much to draw. 

There were also five stations who I tried to work and failed, plus quite a few more that never got started.

Three, real reason No 2, there was an all-time new DXCC on 2m in there for me. At 16:45 I worked T77GO in San Marino. The Serene Republic of San Marino to be exact, that small state surrounded by Italy. I have worked San Marino on 6m recently and famously did not work it on 4m a long time ago. Anyway, that is a new one for this year and for all time on 144MHz.

Four, real reason No 3, there is a new square in there too. 16 stations to work but only bringing one new square shows how well I have covered Italy on 2m up to now. The new square is JN40 in the North of Sardinia which I reached when I worked IS0BQE. For a VHF operator a new square is almost as good as a new country. Almost. San Marino was a new country but not a new square, IS0BQE was the reverse. Take your pick. I have worked 22 2m squares in Italy and I still need 8 more, plus a couple of small wet ones which I doubt I will ever reach. I am still trying for the others.

IS0BQE called me, unlike T77GO who I had to call for a while. Clearly, wherever I am in the 144MHz rare DX stakes it is below San Marino. Sardinian stations might call me, but I have to call San Marino. I know my place.

Five, real reason No 4, is that they (all except T77GO) wanted to work me. Clearly this was true given the number of times they were calling. Either they needed GM, or they needed IO85, or they needed greater DX, or they just wanted to. OK, sometimes I have to shut down the radio for some reason and have to deny somebody a contact. But, in general, I try to work everybody who calls me. Just call be big hearted (or a loser, as somebody termed it).

Within a few minutes of all this starting on 2m, 4m was going hammer and tongs. It was all I could do to watch the displays for 2m, 4m and 6m. There is only so much one man can do. Although things are arranged for me to transmit on two bands alternately, I usually do not do it. I have added various bandpass filters to allow this, for instance to transmit on 4m on one period and then after that on 6m on the other period, or 2m and 6m or whatever. There may be a little desensitisation but not much. Multiband contest stations do that all the time, but they have more than one operator.

I was watching 70MHz while remembering my rule that "higher frequencies count double", even though that rule is nonsense. Rules are rules. So 144MHz gets preference if both are open. Yes, I was also watching 6m and I saw that V51WW was loud and clear on 50MHz. This tempted me onto 6m on the other period and while I was working stations on 2m I was calling V51WW. I called for a long time, as in this case I was joining the pile-up, while on 2m the pile-up was on me.

If learned anything from having a pile-up on me it was that the whole process is random. I had clicked "AutoSeq" on WSJT-X and selected "CQ:Max Distance". You can imagine why - I could hardly have managed the 2m pile-up situation by selecting who to work next each time. The software decided who to work next while I was busy doing logging, DXMaps, watching other bands ... The effect of this is that some stations kept calling and got no reply from me as I was replying to others. It did not matter if those stations were stronger, clearer, more desirable for me to work or anything, if WSJT-X did not select them then I would not work them. That was why I had to decide to go after T77GO as it was possible he would call me and I would answer somebody else.

Anyway, I called V51WW on and off on 6m for about 15 minutes while I was busy on 2m. Even though he was often quite strong, up to -2dB, he did not reply. I know that this has got nothing to do with my signal, just the way WSJT-X and the other software all handle pile-ups. Anyway, at 17:00, just after the 2m opening faded out, I managed to work V51WW.

50MHz contacts at GM4FVM on 9 July 2023

V51WW was an all-time new country (Namibia) on 6m, and also a new square. 8510km was a good distance too. This brings my all-time DXCC worked total on 6m to 93, and means that 2023 equals my best year for DXCC on 50MHz. 2018 was also 69, but that took 12months and this is still only early July.

I also worked LZ3CB and KN32 is also a new square on 6m, bringing that total to 475. Well, 475 after working OH4MDY in KP32 today for another new one.

To round off the day yesterday I also worked EA5JHD and EB3ENW on 70MHz. I would have to say that 4m hardly got a look in yesterday. There are not many new countries left for me to work on that band [??? San Marino Jim] and pretty well everyone has worked me so they do not queue up to reach me on 70MHz. 

It was interesting to try to balance working a pile-up on 2m at the same time as joining a pile-up on 6m. The hunted versus the hunter. Clearly, it does not matter how good your signal is if the station you are calling is using "Auto Seq" in a data mode. However, there are still things you can do which are the standard tricks for getting heard. Watch how the DX station is working, call them at the right time, use whatever sequence they are answering, etc.

Most of all I enjoyed the frenzy of the multi band opening. The totals of DXCC and squares only show me I am making progress. The real thrill is watching the ionosphere doing its thing. 

The band opens, you work some, it closes.

73 Jim

GM4FVM