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.

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…

23cm groundplane antenna

I thought it would be a useful experiment to make up a 23cm groundplane antenna. There is a useful guide at https://vk1nam.wordpress.com/2017/06/24/23cm-14-wave-ground-plane-antenna/

Using some 2mm copper wire from a supplier on eBay plus a N-type female socket the construction was fairly simple. Using the dimensions given above plus a bit for fiddle room I soldered the vertical element to the centre conductor of the socket. For the radials, given it was copper wire I decided to press my jewellers anvil to work and flattened the end of each element sufficiently to drill a 2.5mm hole. Using 2.5mm bolts each was secured to the respective mounting hole in the socket, and then the excess thread was cut off with a Dremel.

Bringing it all indoors – the heavy stuff like drills and hammers live in the workshop – I calibrated my NanoVNA and gave the new antenna a go. It was a bit off but then each element was too long. Trimming each gave a fairly flat SWR where I wanted it. Well, almost, but near enough to stop cutting bits off!

But does it work? Yes, I can open up GB3WC from the shack holding the antenna up inside the window. It’s about two S-points down on the Yagi, or anyway two of whatever the divisions are on the signal strength meter on the FT2D. Surprisingly I can get into the repeater with the antenna on the desk, albeit only coming alway up the signal strength bar and very hissy. It was the same when sitting the antenna in an old bottle as a support – at that altitude there are a lot of houses and trees between us and the repeater.

For a bit of copper wire and a socket it was a fun little thing to make. I actually planned to make a collinear and may still,  but this was nice and simple and quick.

QSL cards

Got a surprise through the door today, 12 QSL cards to my 2E callsign, various dates from February 2020 up to November 2020. Almost all want return cards, absolutely no problem and all part of the fun. I am not a big QSL’er other than eQSL but I always send when asked. Actually, I always planned to sort of back peddle on QSLing until I got the M0… now all I need is a decent design rather than the generic one I had on the M6 and 2E.

23cm first FM experiment

Since my last post about the SG-Labs 23cm transverter I realised I have several handhelds all of which have low power settings. Time to try some FM and get a better frequency readout. 144MHz did indeed produce 1296MHz (and some small change) on the frequency counter. Time to get adventurous – GB3WC in Wakefield is about 15 miles away and pretty much line of sight and so would make a good test.

With the transverter in repeater mode with a -6MHz shift (jumpers 1 and 3 on) and the FT2D programmed for 145.375MHz simplex (WC transmits on 1297.375MHz) – the transverter does the shifting – and the necessary 82.5Hz tone I can open GB3WC and receive it at S9+ on my 8 element 23cm Yagi. In the true spirit of let’s get this new shiny box working this test entailed the use of a microphone stand, some wire and some clamps. But it works.

Only a quick test today as the battery was nearly out on the Yaesu and it’s kind of hard to talk into it where it is. Somewhere I have a headset for it which will make life easier until I figure out how to site it properly. The tricky thing with the transverter is to get it back to simplex means taking the lid off and altering the jumpers, not particularly easy if it’s up in the loft where things are easier to leave in place.

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