Sunday, 23 June 2019

Roundup, Es, RFI, Network Radio, SK sale and a cheering tale.

I've been busy - Giro d'Italia in cycling, Cricket World Cup, all the important stuff. Not bad on the radio either.

At this time I suffer from hay fever. The crop in the field this year is oilseed rape (canola), which cannot be the problem as it has "gone over". The oil seed is now long past its bright yellow flowering stage and it now forming its "pea pod" style seeds from which the oil will be pressed. It is now about 2 metres tall and obstructing the view from FVM Towers.
Behind the fence at GM4FVM, the oilseed rape is blocking the view.
So the obvious culprit is not the the real problem, just like the result I find when I go problem solving with anything electrical.

Sporadic E
This has been pretty good.
4m contacts at GM4FVM 1 to 19 June 2019
Some nice stuff here for me. Best DX being EA8DBM in IL18 at 3278km. EA8 is a good path from here, whilst more challenging  results were to Greece and Malta. My two main possibilities for 4m contacts into Asia are to Israel or Kazakhstan. At various stages over the past few days either or both of these looked possible, but so far no luck. I will keep trying.

I managed to work a new square in Spain - IN93 - in the Basque Country and on the French Border. If I can work JN02 (not sure if there is anyone active from there on 4m as it is pretty mountainous), that would give me another "French" square on 4m. Thanks to OMs in Belgium, Luxembourg, Italy and Spain I have a few squares covering the borders of France. I wish all the rest of French squares would be operational. In the meantime, there are still a few in Spain to collect.
6m contacts at GM4FVM 1 to 19 June 2019
In many ways these 6m contacts are more precious to me as they were worked on a vertical with the rig barefoot. Once again EA8 is the best DX, this time it was EA8AQV in IL28 at 3264km. I haven't really been trying much on 6m. It is on all day, but mostly I use to to see what is being received. Key to the whole project is using 6m (and 10m) to work out which direction Es might open into on 4m or 2m. However, each QSO is valued by me.
I heard WU1ITU, which cannot be a bad result for the half-wave vertical. I also added a few new squares in peninsular Spain on 6m to add to the 4m ones. I still have a few to get on 6m too.

There was even DX to report on 2m where I worked ON4POO again and, more remarkably, Gavin GM0WDD. It is generally easier to work "Winnie" in Belgium at 718km than anyone in Gavin's direction. WDD is only 57km from me. It isn't so much how high the hills are, it is how close they are to you. In Gavin's case we have the Lammermuirs and the Pentland Hills standing between us. A tricky path is as much fun for me to work as grand DX, though of course they all count.

Computer RFI
I have been interfering with myself again.

Computers and amateur radio do not mix well when it comes to Radio Frequency Interference. I can get most problems with USB-type connections sorted out. Ferrites usually do the trick. However, display connections cause me more difficult issues. Lately I have had problems on 432MHz, especially since I improved the antenna. This takes the form of parallel lines on the waterfall and a dull tone in the loudspeaker.

I now have three display screens on my computer. One is fed using an SVGA cable, the second uses a DVI cable, and the third has a HDMI cable. It is the HDMI one which caused the original problem, despite  me having tried to buy a high quality cable. In theory, the ones designed to prevent the data being corrupted by incoming RF are better screened, and should resist signals coming out the other way. Not so, I read that there is not much to chose and random selection of cables is the only effective way to find a good one.

After a suggestion from Tim, G4VXE, I wrapped the HDMI cable in aluminium foil. Perhaps surprisingly given the wonky look of this method, it worked quite well.
Computer display cable wrapped in foil - in this case an SVGA one.
When I did it not only did it reduce the interference on 432MHz to almost zero, the noise level on 6m dropped remarkably. Sadly, interference then appeared on 50 and 70MHz, possibly now not masked by noise.

I then tried ferrites on the other two leads, and changed the SVGA cable. Those two changes resulted in the lines on 50 and 70MHz disappearing. Wrapping the other two leads in foil did not make much difference.

So that seemed to remove all this interference. however, it seems to be lurking in the background, albeit at a low level. Unplugging the HDMI cable and plugging it back in clears a very weak set of traces. Next I might try changing the display board in the computer, and making sure it has a good ground connection.

Frustrating. I seem to be chasing myself around.

Network Radio
I have said before in this blog that I have no problem with network radio. I have an Inrico TM-7, though I can also access network radio using an old mobile phone or a laptop computer.

Someone said network radio is not real radio. In my view is isn't amateur radio, but it is "a thing". Who cares how to define it? It is good way for amateurs to communicate, especially as local FM has gone quiet and, anyway, network radio lets you communicate with "locals" all over the world. It is like the KST chat site without the keyboard nerds who cause me such grief (or they would if I used KST).

Speaking of Tim, G4VXE, it was he who let me know that he has started a VHF/UHF FT8 forum on Zello - Zello is the "PTT" (push to talk) software used by millions worldwide. I have joined this group. It is early days and only a few of us are one it, but it has potential to provide a talk-back channel which could be useful.

More from the SK sale
I spoke before about "Roland" and his equipment disposal turning into an unseemly clearance/ destruction operation. Well, a couple more things have turned up for me to buy. One was a spare microphone for an IC-7100. I am not sure why Roland needed one, but I can use one for my own IC-7100. Mine was one of the first shipment which had the basic microphone, now I have bought a keyboard mike.

Secondly, and separately, came an MFJ "Intellituner". MFJ-929. This is an HF auto ATU, which might not sound like the obvious thing for me to have. A useful feature it has is that it can select between two SO-239 output sockets, depending on the band in use. As this item also left Roland's shack minus power cable, minus the rig cable and minus a handbook, I did not immediately recognise what it could do.

As it stands, in addition to being an auto-ATU, it detects and displays the frequency of the transmitted signal plus it provides SWR and power output data. It also selects the appropriate antenna based on information stored in its memory. However, it needs an RF signal to do this. Once I make a rig cable for it, it should be able to detect the band based on the band data coming via the ATU socket on almost any commercial rig. I do not know if this one works, but in theory this should be able to select between my indoor 10m dipole and my long wire, and thus it may well become a handy addition to my shack.

I think that is it from Roland. Things have kept turning up, without boxes or leads. Hopefully, when it comes to some other individual picking over my radio left-overs they will find all the boxes and manuals (and certainly the leads).

Some Youth Work
No, not me. DH8BDA writes a good blog, much more to the point than this one. There is a link on the sidebar of this site.

A while ago he wrote a posting about his step-daughter's electronics project. I will put a link to it below. Sure, Olli strayed from the core radio topic here, but I thought it was a lovely piece.

It is well over 50 years since I started radio construction with my Philips and Sinclair Radionics kits. I was not trusted with soldering, so I had to put up with the Philips ineffective spring joints, or Sinclair's bolt-together components with colour-coded bases. These things got me going. I remember the joy of it. Even more joyful was the experience, as a 10 year-old, of being excused the woodwork examination at Primary School so that I could build a crystal set for the teacher to listen to. Wow! I rose in the teacher's estimation and became class nerd, and both at the same time.

I would like say that these things are "character building". Maybe we do not know how that character will develop. Perhaps Annie will never build another electronics project, or she may become obsessed with it. Who knows? I do not think it matters. The joy is in the achievement of the project.

The key phrase is that Annie is "interested in how things work". With that curious approach she should go far.

By being creative we grow. That might be creating a radio, or a garden, or a model of the Titanic made with match sticks. The point is that during this voluntary task we allow our imagination to run free, we show ourselves that we can work through a project, and eventually we can appreciate it. Saying "I did that" is a great reward.

She didn't have to build it it; she chose to build it it.

Thanks to Olli and Annie for cheering me up, and for reinforcing my confidence in the young people of today.

If you have a minute it is worth reading. You can find it here...




Wednesday, 12 June 2019

Antenna roundup, and "leave means leave" when it comes to 10 metres.

In the seminal BBC comedy programme "The Fast Show", one of the regular sketches was "Jesse's Diets". Jesse, played by the excellent Mark Williams, would come out of his shed and explain what he had been eating. "This week, I 'ave been mostly eating ... (something bonkers)". Such as this gem ...

This week, I 'ave been mostly eating ... Raspberry Pop-Tarts!

This always left me wondering what on Earth it was all about. That other superb comedy show "Father Ted" had revealed that the influence of God in the creation of Pop-Tarts might me more limited than we thought. Be that as it may, I suspect that a week of Pop-Tarts for me would have a major effect on the Berwickshire plumbing.

So, this week I have been mostly putting up antennas.

I have never eaten a Pop-Tart. Can you still get them?

1) 432 MHz

My experiment on 432 MHz has taken another step forward.

What I wrote here on 19 July last year was ...

This is not an Earth-Moon-Earth capable 70cms set-up. Or at least, it isn't designed to be. It is designed to be vastly better than no setup at all. Adequate, not excessive.

That meant 35W barefoot.

By 20 November last, at which stage I had worked several stations on 70cms EME, I wrote ...

Erm. I was wrong about that.

By that stage I had developed the station to 95W output and I was using the 70cms part of my Antennas+Amplifiers dual band yagi.

It is not like me to decide on a strategy and then change my mind, now is it?

As someone said, "if the facts change then I change my mind".

OK, I have now completely abandoned the idea that 70cms can ever be some sort of half-hearted lash-up on my part. The facts about 70cms have changed, at least in my mind.

I am getting more serious about 432MHz.

I now have up to 180W available and I have put up an 18 element DK7ZB yagi. This means that the old 7 element 2m yagi is now back on the mast too as, instead of a dual band one, I now have two separate beams.

First of all I came across a 180W TE Systems linear, a model 4452G, second hand on eBay. This is my third TE Systems linear. Just a matter of arranging some thermostatically controlled fans, a hefty power supply and a power output meter.

One consequence of buying the more powerful linear is that the Mini-70 masthead pre-amp, grand as it is, has to go. It is limited to 150W on SSB. It might not like 180W of JT65 100% duty cycle for a minute at a stretch. So I have replaced it with a much higher rated MVV-144 pre-amp. The performance of the two pre-amps is not very different, this is purely down to power handling.

Yes, if I had gone for a better specified 70cms station at the start then changing the pre-amp would not have been necessary. As I say, I was wrong about that. Or, my understanding of the facts has changed. I had felt pretty sure that 432MHz would soon prove to be to difficult for me to work on, and I would stick with 35W. Wrong, wrong, wrong. But wrong in a nice way, as it was better than I had expected.

Not that putting up the 70cms beam was without issue. Wimo had sent one of their much-vaunted element mounts the wrong size, plus the water ingress plug on the end of the boom had broken in transit. I must chase up new ones from them.

I can now hear more RFI coming from dozens of devices in surrounding houses, so it must be better.

Adding 70cms means that I cannot be serious about 5 bands at once. Some simplification is needed down the spectrum, especially on 6m and 10m.

2) 144MHz

Also upgraded was the old Wimo 144MHz beam. Before it went back up I took the opportunity to change the dipole driven element for one capable of more than 200W. For the same reason as for 70cms, I reckon that 300W of JT65 on moonbounce will require something with more in reserve. Not that I generally run more than 200W, but wouldn't you know that the night I turn the wick up to catch the DX will be the night the balun blows up? JT65 is very demanding in terms of power handling.

The new higher-rated element did not come with screws and spacers, so I guessed they expected you to use the old ones. Not that it was easy ...
The screw and sleeve on the old low power dipole on the 7 ele 2m yagi, which I needed to reuse
Getting the old sleeve off that old screw was a big issue, and it involved Mrs FVM using vice grips, while I gamely destroyed the head of the screw in a vain attempt to release it. The sleeve had turned itself into a threaded sleeve simply by corroding itself solid.

In the end I had to saw off the screw head and then bend the screw before wrenching it round. That way I screwed it off the spacer. It is amazing how strong corrosion can be. All that had happened was that the screw threads had been filled with solid oxidised alloy - which turned to dust when a lot of pressure was applied.

Next issue - I had no screw the right length. Lots of screws the right width, but nothing anywhere near long enough. Then I had to go to a local institution - "J H Wood Engineering". These people have provided me with aluminium poles, brackets, tools and even the 4.5m rolled steel joist holding up the house roof. This time I needed a small screw of considerable length. "Certainly" was the reply, and they charged me 50 pence for four screws exactly the right size (not even requiring cutting). Job done.
2m and 70cms beams at GM4FVM
3) 70 MHz
After a test with my old dual band 4m/6m Vine, I have concluded that my 4m antenna can happily go on my CUG mast. The 6m antenna used to pick up a lot of hash from the kitchen appliances, but 4m doesn't seem to have this problem. The 5 element PowAbeam has come out of the garage after a few weeks and has been replaced there by the Vine.

4) 50 MHz
After a different test on the CUG mast, my old Moonraker multiband 6m/2m/70cm vertical has appeared on the pole formerly occupied by the 4m vertical. The collapse of local activity means there are no contacts to be had on 4m FM any more. I cannot justify a 4m vertical, so this makes more sense.

The test also showed that the Comet diplexer was very lossy, so this is now a 6m only antenna, the 2m/70cms side having reverted to the Diamond X-30 on the CUG mast. A long time ago I used to use a simple 1/2 wave vertical on 6m with a gamma match - that might be better than the Moonraker as a single band antenna. The Moonraker has a counterpoise for 6m which I doubt is very efficient. Anyway, it works after a fashion, which is enough for now.

I am using the Moonraker barefoot because my 6m linear is gradually getting more and more cranky. 6m linears have always been a disaster area for me, but at least this one came second hand and it has lasted for years so I cannot complain (?). However, I have spent ages fixing it and my patience is now running thin. Doesn't matter much if I am just using a vertical. I have set the linear up in case I suddenly hear Japan (ho ho), but I am not using it.

5) 28 MHz
The whole "simplification" idea is that I have moved up a band. Before I used 10m as a guide and pursued DX on 6m, 4m and 2m. Now I hope to use 6m as a guide and work DX on 4m, 2m and 70cms. So I can give up on 10m. I took the 10m 5/8th vertical dipole down some time ago.

This is a clear strategy and there is no going back. That is why I took down my 10m vertical.

So right away, straight after explaining why I was giving up 10m, I decided to go back on 10m WSPR with an indoor dipole. Well, I have it, so why not use it?

I do wonder a bit about this strategy stuff. I mean, when I decide to go over to four bands, why shouldn't I change back to five bands, almost in the same moment?

You don't get responsible people fiddling about like that. I mean, you would not find a government keeping on changing policy, saying one thing and doing another, getting lost amongst the many options and so forth. Governments do not plan something and then abandon it before it has proved itself, or change it even before it has come into effect. You never see that, do you?

This looks like a settled line up. What with the IC-7100 and transverter working well on 2m, there is nothing left to change. I can sit back and enjoy a stable set-up. At last!



Thursday, 6 June 2019

IC-7300, split IF, RF attenuator, transverter and ALC power spike

Now there is a complex title, designed to pick up every internet search ever invented.

Usual warning. This is a modification to a commercial radio, the Icom IC-7300. This may invalidate any warranty, so do not do it unless you appreciate the risks.

Usual assessment. The level of technical difficulty of this modification is, even by my standard, " very low".

The Problem
When I bought my ME2HT-Pro 2 metre band transverter I could see that I had found a superb performer. The thinking went that a device designed to work at maximum performance on a single band should be better than a multi-band rig. And so it proved. It really is superb. The only doubt I have surrounds its frequency stability while subjected to temperature changes generated on transmit. This issue needs to be resolved as I bought the high-stability version to avoid any trouble. It could be one of those snags which only exists in my head and not in reality.

I ran it initially with my Kenwood TS-590SG, but later I got an Icom IC-7300 which looked like a great combination. Gabi, who makes the transverter, suggests it as a option. Then a real-world problem arose because the IC-7300 puts out an RF power spike when going to transmit. This is common to many rigs as almost all use the ALC circuit to reduce the power. In the moment the radio goes to tx there is no modulation and the ALC is not active, leading to a momentary spike. Potentially this could be full power, which for the IC-7300 on 14MHz would be 100W, but in reality is lower than this. Another problem is that the spike is of very short duration, so it is very difficult to measure or even notice that it is there.

Anyway, undaunted, I connected the IC-7300 up to the transverter. I screwed the RF power output down to 1%. Every time I went to tx the output power LEDs on the transverter went full scale. Clearly these LEDs react to a short spike when my other meters don't. With the transverter producing 25W as shown on the LEDs (it is capable of 50W), the spike was lighting up the whole scale up to the 60W red one at the end of the scale. Scary.

With the transverter configured to 5 watt maximum input but adjusted to run to about 50% power on around 1 watt, this means that the spike must be more than 2 watts and quite possibly more than 5 watts. It proved too short to show up on conventional meters. I could only assume that it was in the 5 watt region or more. Recently I read a suggestion that it peaks at 25W.

This just compounded my often-stated reluctance to operate anything like a transverter on a single IF lead. All that has to happen is for the PTT line to fail, perhaps through tarnish on the plugs, and the TX transmits into the sensitive and expensive receive input section. Result: I would blow the whole thing up. Not that in 40 years of using transverters I have ever blown one up, but Mr Murphy would ensure that if I ever did it would be my best and most expensive one that went arrrggghhh.

The solution
Finding a solution to this problem involved a lot of debate with David, GM4JJJ, in the months before he sadly became silent key. The various ideas always involved splitting the rx line off from the tx line inside the IC-7300 (relays are too slow), ideally in a reversible operation. Then some way needed to be found to reduce the output power of the IC-7300. These two elements, tx and rx, would then be connected separately to the transverter in the same fashion as the TS590 used to be. But how to reduce the output power?

Well, those nice people at Kuhne Electronics make a board but I was disinclined to use it. There have been reported cases of PA instability and self-oscillation. I am sure that in most cases it works fine, but I also thought that the power handling of the resistor looked low and the soldering looked fiddly plus I don't like phono plugs for RF and then you have to take the board out to return the rig to normal use and ... I just don't like it. DB6NT's products from Kuhne are no doubt superb, but once again I am looking elsewhere.

INRAD make a simple kit for the IC-7300 to split the rx from the tx. It also uses phono sockets and costs £50 plus postage from major UK amateur stores. A bit more searching revealed a better one on eBay with SMA sockets and at a price which worked out at £22 with free postage. Not a difficult decision to make.
{EDIT} I hear in May 2020 that the eBay link above may no longer be available. Not sure if the product still is, but the INRAD one is currently still availble in the UK from Nevada and possibly other sources.
I thought about various ways to reduce the IC-7300s output power by isolating the PA. David doubted that this was practical, and eventually I realised he was right. He usually was.

I have finally decided that the simple thing to do is to reduce the output power with an attenuator. I did not go for that immediately as I associated RF attenuators with calibrated products which come at enormous prices. This is true - my first checks revealed that a 20dB 100W attenuator costs about £500, putting the whole project beyond economic viability.  Also, the range of power and attenuation is rather limited.

However, I then checked Amazon and found a shed-load of lower spec attenuators for £30 or less. There were cheap ones with few details, but also a mid-priced one direct from the manufacturer. Tracing back from the Amazon photo, I found the manufacturers website and even found something approximating to a data sheet. Suddenly, thanks to Amazon, there was lots of choice, no need to settle for a limited range of values available in the calibrated ones.

I did some calculations based on my assumptions about the power spike and the attenuator network in the transverter, and this came up with 10W for the spike which would need a 10dB attenuation to render it insignificant. I decided to go for a 25W 10dB attenuator. I doubt if the spike is 25W, but that seemed the best power/price option with a safety allowance for my guesses.

Installing the components
It wasn't difficult. The "RX Adapter" from eBay arrived from France quickly. I needed some support from the seller Daniel who could not have been nicer or more helpful.
IC-7300 RX Adapter from "hifi1200" eBay
There were no instructions but it is pretty easy to install. Just to be on the safe side I downloaded and checked the INRAD instructions - I'm not proud. All you do is to take the top covers off the rig (14 screws, including the ones round the speaker), pull the ATU socket out and turn it safely back inside the rig, replacing it with the adapter board. Then pull out the RX plug from the rig and connect it into the back of the adapter and then plug the adapter's plug into the empty socket. Clip on the filter. Then put the covers back on and test.
Adapter installed with the ATU socket twisted back out of harm's way.

The kit includes an SMA to SMA patch lead which returns the IC-7300 to normal operation. This makes it an easily reversible modification. After checking that this lead worked (it did) I took the patch lead off again and connected the rx feed from the transverter and the IC-7300 was working perfectly on 2m. The only slight snag is that the SMA sockets are a bit wider than the ATU socket was so the top cover of the IC-7300 shows a very slight bulge over the sockets. Not a problem for me as I don't look at the back of it much.
The neat board showing that the nuts round the SMA sockets are wide. They slightly bend the covers when fitted.

Moving on to the transmit side, the "RX Adapter" modification changes nothing. Thus the full power still comes out of the SO-239 socket on the back of the rig. The attenuator was being sent from China and took a while to arrive. Actually, it was just over a week! During that time the RSGB "Rad Com" arrived and in it was an article for a satellite transverter-type thing which also used a similar attenuator. In the article the author, Giles Read warned against connecting these devices up "back-to-front" as they have much lower power handling that way round (I wonder why). He said that they had an N-type plug which could be connected to the rig at the input end. I checked all this out with Giles who was very helpful. I think I have it the right way round.
RF attenuator from Amazon.
The device duly arrived with no instructions so the RadCom article had informed me as to which way round it should go and the danger of getting it wrong. I am never keen on screwing anything heavy like an attenuator directly into the SO-239 socket on the back of the radio. The weight will tend to distort the socket. Anyway, it would need an adapter or for me to shell out money to convert to an N-type socket on the IC-7300, only to hang a heavy weight on the end of it.

So guided by the Rad Com article I spent the time waiting for the packet to arrive from China by making up an unusual lead - PL259 plug at one end and an N-type in-line socket at the other. Surprisingly, I did not have one of those leads in my spares box. I hate plug sense RF adapters anyway.
PL-259 plug to N-type socket lead - you know you want one - and the attenuator.
By making the lead I did the only soldering required for this modification.

When eventually set-up with all the leads and the separate rx and tx, the transverter was still set to 5W from previous use with the IC-7300 in unmodified form. So I decided to try this and adjust the sensitivity using the two pots in the transverter.

The present order of things is that the IC-7300 RF output is set to 25%, notionally 25W. Very little output power is showing on the IC-7300 PO meter because output is limited by the mic gain for SSB or PC drive for data. This produces around 9W out of the IC-7300 on 14MHz.

The spike power is not adjusted by the power output control on the rig, so the object of the exercise is to reduce whatever it is by the same amount as the wanted signal which is influenced by the output control, and then re-balance them.

Trying to measure the attenuation accurately is beyond me. I do not have calibrated meters. The figures suggest that it is around 6dB but it could be more. Given the limitations of the meters I have then it could well be 10dB, but I wouldn't buy one from Amazon expecting to use it for measurement purposes. Spend £500 on a proper one if you want to do that.

The RX Adapter has split the rx and tx leads meaning the risk of blowing up the transverter receiver has gone. The attenuator has reduced the power into the transverter to around 2.5W. The spike is no longer visible in the transverter output LEDs.

The introduction of the attenuator is to reduce both the spike and the wanted signal by a fixed amount. So, assuming that before the mod the spike was 10W relative to an maximum input signal for the transverter of 5W. After the mod the spike should now be reduced by the attenuator to about 1 - 2W (depending on whether it is fully 10dB or the 6dB I think it might be), well below the maximum input power. I have adjusted the wanted output from the rig upwards to show 2.5W at the transverter. So the wanted signal should now be more than the spike, which the LEDs seem to show.

In reality I don't know what the power of the spike is, but I used to be able to see it higher than the wanted signal in the LED meter, and now I cannot see it at all.

There is no sign of the attenuator getting hot, but let us wait for an opening or a long Earth-Moon-Earth session to establish that for sure. I am pretty sure that the spike is so short that there won't be much heat in it, just enough voltage to do damage with the old set-up.

So far so good. Time will tell how it is judged in the long run.

I really like the IC-7300. It is not designed to work with a transverter, hence the modications. It does not feature to alter the readout for a transverter, which the TS-590 had. However, the TS-590 one didn't work very well anyway so I had it set to the IF frequency in any case. So either way it says 14.174 rather than 144.174. I can live with that.
IC-7300 on 2 metres, with 110hz correction checked against a GPS locked beacon. Not much happening.
Other thoughts.
This plan was hatched before the appearance of the IC-9700. I suspect it is a match for the transverter on 2m. It would make a great 2m radio for me. However, I have the IC-7300 and the transverter, so I should use them. Do not rule out the possibility that I might change to a VHF rig eventually, if only to get rid of the rats nest of wires.

It was also hatched before I suddenly became the owner of a second IC-7100, acquired in the SK sale. I didn't really need it. It works well enough on 2m, but not as well as the 7300+transverter combination. Still really good for 70cms where I have nothing to compare it with.

You should hear it. Relays in the rig (now not switching the RF), the transverter, and two in the linear, all sequenced and clicking in order one after the other, and then in reverse after tx, plus three fans independently doing their thing. Bang, crash, tinkle every 15 seconds. It sounds like it used to do in Knockmore Junction Signal Cabin when we signalled the Derry Fitted Goods off the Antrim Branch. That was what railways in 1967 were like, but not any more.

I hope that David, GM4JJJ, would have approved.