More ATV fiddling

After finding the dead LCD screen that was to be a 5.6GHz ATV receiver it also turned out that the 7″ Pi screen on my Portsdown setup had similarly died – just white lines on the screen. No amount of stripping, reassembling and general fiddling fixed it. A new screen did.

Anyway, I now have a Winterhill receiver. This came from a fellow ham and saved me building one. As is usual with any new box one absolutely must try it right away, which is how I discovered the bust screen on the Portsdown. After that was replaced I successfully sent a test card 40 inches across the desk! Small steps… and at least the Winterhill is in a nice box unlike my Portsdown which is still waiting for a suitably sized case – why is it all the nice metal boxes are a few mm lower than the 7″ display needs. Huh.

5.6GHz experiments

I had a quick fiddle with the box of bits that should by now – in fact by a year ago – be a 5.6Ghz ATV transceiver. I now have a couple of Gibeon flat panel antennas which claim 24dBi as mentioned in the excellent resource on this topic at http://5-6ghz-atv.co.uk/

So, let’s have a play. I got a rather old fashioned Sandisk Photo Album, a slab of plastic that takes 5V and will present photos (and videos and sound files) to a TV via an AV output and the typical red, white and yellow RCA plugs. First off I  needed to make sure this worked. So, what has an AV input… er… Bedroom TV? Nope. An older Sony TV in another bedroom does and so it was plugged up. And nothing. Problem 1, it seems to take an age to turn on in response to its remote control. No switch of course. Problem 2, it would not read anything on the SD card I had with a test card image on.

The only clue is it needs a ‘JPEG (Baseline, up to 16 Megapixel)’. No idea what I had produced via GIMP on the Linux box but it would not find anything at all. Maybe it’s the SD card. I found a very old 32Mb (!) SD card with some sundry photos on and those were fine. Ah, so maybe it cannot read big SD cards. Copied the test card file onto that and now it at least finds the card but says the format is unknown. After 3 iterations I fed the jpeg into Windows Paint, saved it (as jpeg) and it worked.

And success, I can send the test card image to the TV via the TS832 transmitter and RC832 receiver. Next, I tried the flat panel antennas and they worked too, not that I would have expected any less as the little rubber duck antennas worked fine.

However, offering the AV to my 12V monitor (ex eBay car reversing screen) just showed lines. No amount of shouting fixed this and it would appear that this monitor has simply died, perhaps having got fed up waiting in a box all this time.

Anyway, now I need to actually construct the thing properly and work out a mount for the antennas.

Spectrum analysers

I’ve been looking for some time for an affordable (i.e. used) and useful ranged (i.e. not cheap!) spectrum analyser. Obviously I want DC to light but don’t need it and don’t want to sell the house for a bit of test gear. I have a TinySA which is good to 960MHz but I will need a higher frequency range as I fiddle more with microwaves.

The ultimate, e.g. a Rigol or Siglent LCD type device is just far too expensive. Nice to have yes but something one would need to be using all the time in order to justify it. Then I came across Satsagen – http://www.albfer.com/en/2020/02/21/satsagen-2/

Satsagen runs under Windows and by default uses an Adalm Pluto as its interface to the real world. The software even does the necessary to upgrade the Pluto to the ‘full’ range of 70MHz to 6GHz (you can do this easily by hand but it’s nice of the software to do it anyway). The software has three basic function too – spectrum analyser, spectrum analyser with tracking, and generator. So, one PC, one Pluto, Satsagen and you get a pretty decent 70MHz to 6GHz spectrum analyser, tracking generator and signal generator.

I have not yet delved into all the functionality and only carried out a couple of quick tests on a handheld and on my 70MHz transverter, plus a very quick test of a FPV transmitter (TS832) up at 5.6GHz.

It will work with other devices such as the HackRF and the RTL dongle but it seems so useful I purchased a Pluto just for it (yeah, ok, I can use it for other stuff too but hey)

Antenna fiddling

I’ve been investigating putting some antennas outside and not getting very far. So I got a 2m ‘big wheel’ antenna off a trader on eBay. Plan A was to build my own but, being lazy I purchased a Wimo one. I’ve just installed this in the loft, directly above the shack so no issues of distancing (!) and it is a lot bigger than I had pictured. I now need to crawl under the thing to get to the fan dipole and other less important things such as the plumbing feeding the shower… hmmm.

Anyway, it all went together without much struggle and the NanoVNA shows a decent low SWR across the 2m band. I’ve had to rearrange stuff so the 4m dipole is now where the 2m one was and had to be rotated 90 degrees so is now roughly north-south.

Initial PSK Reporter results from the big wheel – note both the 2 and 4m antennas are fed from transverters from the transverter store in the Ukraine – showed 2m FT8 results of -14db into Cornwall and -10db into Cork plus a decent spread, and 4m picked up in south Wales so no worse than before. Of course, all these reports will probably be from stations with far better antennas than me, but hey.

The next task is to build a halo for 4m. I have some metal on order for that and other projects, like a 4m ground plane so I can do vertical as well as horizontal.

All still in the loft of course. One day these will be outside getting wet…

More on the ’75

Having now had a chance to take a closer look at the Creed to see why when Y is sent by the TDMS it prints as Z it is clear why! The following shows why… the TDMS is sending a continual stream of Y’s and then R’s:

This is the system between characters, all is well, but…

…this should be a Y, i.e. MSMSM (M = mark, S = space), but prints a Z, i.e. MSSSM.

And the R? This should be SMSMS, not SMSSS as shown. SMSSS is carriage return, no wonder then why the typehead remains firmly at the left of the platen.

But, checking the waveform output from the TDMS shows it is indeed sending a Y, and with a good square wave. This gets rather mangled when the teleprinter receive coil is connected but still has sufficient peaks to drive the thing. So the issue is between the input to the teleprinter and the selectors.

One item to note though is the three photos above are from a video recorded on my iPhone in ‘slo-mo’ – which proved to be really very useful here!

Time to read the manual more closely…

Antenna experiments

I’ve been planning for a while now to put up an antenna in the garden, but where is the question. I have a 20m wire and 9:1 unun to set up somewhere – ideally I’ll run this up the garden but that goes under the phone line, or actually the end of the wire would be under it. What stopped me was the impending changes for EMF as the unun would be mounted outside pretty close to our bedroom window.

So, for a laugh I got another unun to experiment with (yes I know I can make one but the ferrite I had is lost in the workshop moves). Looking at the ‘ideal wire length’ chart 36 feet comes close enough to the distance between the bedroom/shack and the hedge so I cut 36 feet of bell wire and launched it across the utility room towards the workshop as a measure. Tied to the bedroom window reached almost to the far side of the workshop. I reckon I can attach a pole there and attach the unun to the wall outside the shack – there is a convenient airbrick nearby. But, for a laugh I attached said bell wire to the unun, hung the unun on the window handle, ran about 6m of RG58 across to the tuner and tuned it up. The YT-1200 actually managed it right down to 80m (the loft fan dipole will not go longer that 40m).

But the FT450D was very unhappy trying to feed power in to any band under 20m. A string of clip-on ferrites cured that and I managed to be heard on FT8 in Eire and Germany on 80m plus managing FT8 contacts on 40m and 30m.

It is deaf – no surprises there. The bell wire is not taught so it almost touches the garage roof on the way down. A proper bit of wire stretched up may be better and I have a reel so more fiddling may be had yet.

The icing on this experiment was being heard, FT8 again in Finland on 60m and later managed an exchange with a French station – my first ever anything on 60m. Oh, yes, and I have that ‘Hold Tx Freq’ checked so it doesn’t stray outside our limits… worth remembering that because had it tracked up to the French station it would be out of our rage.

The downside is its getting very cold in the shack with the window open! 

Creed 75 progress

Work on the Creed 75 is slow at present and not helped by the fact the workshop is a mess since I moved all the valves in there and thus had to relocate all the other junk. Having recently reminded myself that 1/4 watt resistors do not generally like being expected to sink 3 to 4W (!) I have some decent resistors to ensure the PSU gives the required 20mA. So I have 80-0-80V from the PSU attached to the 444, I have 20mA (actually 23), the 75 types to itself locally, which is mechanical, but does not receive correctly.

I am generating code from the TDMS but Y comes out as Z and most other code combinations are unrelated to reality. I wondered if this was the result of the typehead not lifting correctly but Y and Z are on the same level. The ‘scope shows a reasonable waveform coming out of the TDMS.

So, currently I have two teleprinters and neither one reliably prints out what is sent to it. Nor do they talk any sense to each other. I can accept that with the 444 as I still need to strip it down but the 75 is all functional mechanically. The code combinations ‘sound’ reasonable too (if you’ve never heard a teleprinter you won’t know what I mean here) as with the motor off the clacking sound seems reasonable for the codes being sent by the TDMS. Very unscientific I know but it backs up what the ‘scope shows.

Some adjustment needed then… but really as I have yet to have any baseline in any of this it is a bit of a moving target. The TDMS will not send just one character but in theory, and with the motor off, given it sends the same character continually it should set the selectors correctly for me to examine them to see if Y as sent really is Y as received. That’s the next step, only the bench the teleprinters are on is too crowded to work on them.

The fine art of equipment repair

While viewing the UKuG webcast last night I lost the RHS sound in the headphones. Fiddling with the wire made no difference. The headphones in question are plugged into an audio mixer that connects the radios and PCs. Checking the speakers which are on a different output from the mixer showed the same issue, LHS sound only. As I wanted to watch the webcast I unplugged the headphones and plugged them directly into the MacBook, restoring the audio.

Today, I pulled the mixer out and checked all the plugs. Checking audio from the FT450D showed it, too was only LHS. Hmmm. Figuring out it was probably time to take the mixer apart as fiddling with the pan and level knobs and main slider made no difference I caught one of the push buttons and heard a crackle. Pressing this a couple of times solved the issue. I do like these faults, just fiddle with everything and swear at it to fix. Brings back memories of the house TV in ancient times that would sometimes need a good thump! Very scientific…

Now, do I bother finding the switch cleaner or leave it well alone and hope I remember which switch to abuse next time…

Satellites

I finally got myself a handheld satellite antenna – an Arrow II. It packs away quite small and is easy to put together, albeit you need to remember the size of the 2m elements when waving it about if constructing indoors like I did first time. I got the one without the diplexer because I plan to use two handhelds for full duplex rather than acquire a full duplex radio.

Of course, the first order of the day was to try to bounce APRS off the ISS, in which I failed while waving said antenna about the shack. I received APRS easily enough but it was just too hard to try to track the ISS from the shack. I missed the good pass because the FT2D was refusing to see the GPS and I had not stored local coordinates – I have now.

So, day 2 and I assembled just the 2m elements outdoors. Turned the FT2D on and it found the GPS almost immediately. I wonder just how much lead paint is on the shack walls! After figuring out where the ISS was on what was quite a low pass for us I picked it up and, finally got a call in. The following are screenshots from ariss.net:

The actual ‘raw’ data as reported on ariss.net was “20210414100126 : M0RVB-7]USUPTS,NA1SS*,WIDE2-1,qAU,DB0NU-10:`w?pl [/`Hello from IO93_(“

Next time I will try to reply to APRS ‘calls’ but this time was just a trial run to see how many arms you actually need. I can well imagine the complexity of tracking and calling through a LEO satellite, and logging as well. Anyway, this harness, which came via Amazon and was only just over £8 may work… not properly adjusted yet but seems to fit the bill:

New toy

So I now have a functional Creed 75 teleprinter. The person it came from had done a first rate job at cleaning it up and getting it to function. Thus far all I have done is put it in the workshop waiting for me to make some time and space to have a play. I also need to get my head around it as I have never had a 75 before.

And here it is. It is in good shape given how old it is and I hope eventually to be able to sneak this into the shack, aka the little bedroom. There is just no way the 444 would hide in there but there is almost a 75-sized hole.

The innards do look neat and care has been taken in getting it working.

More to the point though it prints just fine, a stage I have yet to reach with the 444.

The first order of play is to get some volts onto it via the TDMS and make sure it receives as well as sends. Ah, that means I need to fix the TDMS which has stopped working. This also means I need to rearrange all the valve collection as this is taking up half the workshop right now. Snowballing…

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