Idea Box : Multiband QRSS receiver.

This idea is from some years ago, when the QRSS frequencies were (mostly) harmonically related.

Today I would probably use a SI5351 (3 output clock generator) as local oscillators for three receivers.

From 2009 :
This could be extended to 3 or 4 bands with some effort, but here is the basic idea :

I have some Crystals on 3500 , 7000 and 14000 kHz. This could make for an easy setup of a dual band grabber using a single local oscillator :
Here is the trick : 
- make a single oscillator on 3500 kHz - use two buffers (possibly use the gates as buffers)- take one signal and use a direct conversion receiver circuit on 3500kHz, using the crystal filter of Joachim's QRSS receiver
- take the other signal and use the 3500 kHz LO signal for a receiver almost exactly as PA1GSJs receiver, 
- making it a *simultaneous* dual band grabber receiver for :- 3500.800 - 3500.900 kHz- 7000.800 - 7000.900 kHz
Of course, the same idea could be used to make a 7000 / 14000 kHz dual band grabber receiver using 7000 and 14000 kHz Crystals.
There is even the option of making a doubler for the 3500 kHz signal, using this for extending the dual band grabber to a 3-band grabber for 3500/7000/14000 kHz.
Actually Joachim and I have been talking about the 3-band idea, but I have come to think that the 2-band idea is better in terms of simplicity of construction


Very Simple QRSS Low Cost Grabber Idea.

I did not come up with the idea, but Radovan, OK1FCX on the QRSS mailing list did.

Here is the basics :

Use the cheap Pixie 40m TRX and a Raspberry Pi running QRSSPig, a program created by Martin, HB9FXX. This could be done within $50 for a complete grabber, uploading the grabber files to a free service like qsl.net, which is just for HAM radio.The crystal in the original Pixie is on 7023kHz, so a bit far from the frequency normally used for QRSS on approx.  7040kHz.

Now, OK1FCX used a 7030 crystal (the European QRP frequency on 40m), so got the audio frequency down to about 10kHz. It is possible to reduce that audio frequency to about 5kHz with a 7035 crystal available from Box73.de . However, I am in possession of a single crystal on 7038kHz, brining the audio frequency down to about 2kHz. It may be possible to adjust the crystal to fit in with the WSPR frequency on 40m, so the receiver could do double duty as a WSPR and QRSS RX.

Somewhere I should have an almost finished Warbler TRX, modified from the original 80m frequency to do 40m WSPR. If I can find it after my move, I should probably use that for a more permanent solution, but that is beside the point of the "cheap and dirty" QRSS setup. I should probably use one of my 7030 crystals as Radovan did.

In addition, the 40m Pixie could be used with crystals (that I have available) on 7000kHz to monitor the old (and maybe not used any more) QRSS frequency of about 7000.9kHz

I may have to ask on the QRSS mailing list, if more than one instance of QRSSPig can be run on a single Pi. How about a $50 dual frequency grabber ?


Raspberry Pi SBCs and FT8.

Several years ago I purchased the second version of the Raspberry Pi (RPi) single board computer, a low powered PC costing about $35.-.

I did a few experiments with that one, and it has been in the drawer since I moved back to DK.
A few days ago a friend came here, and we pulled out the old RPi, and played a little, just with the command line interface.

The later V2 and 3 versions have much more power, having quad core processors, and the 3B+ having a 64 bit processor and a higher clock frequency than any of its predecessors.

I have a few RPi2s lying around unopened, and now I ordered (locally) two RPi3B+s.
As far as I know, the RPI2s can run the WSJT-X program, so one of the first experiments will be getting that program up and running on a RPi2, possibly running it from another screen (PC) via VNC. We shall see if the model 2 can support that, but I suspect it can.

Some time ago I purchased some single frequency QRP transceivers (superhet) running on USB on the JT65 frequencies, on 15, 20 and 40m. Since those differ from the from the JT65 frequencies by 2kHz on those bands I think it is possible to modify them by pulling the LO crystal. We shall see how that goes.The idea is mounting those small TRXs together with a couple of RPis, so full monitoring of all those bands simultaneously is possible without occupying a full HF TRX for just that purpose.

If the crystal pulling gets too tricky, e.g. insufficient frequency stability, I have some Si5351 boards with up to 3 frequency outputs between 8KHz and 160MHz.

Maybe getting some simple receivers up and running on other bands, releasing other TRXs for more general use.

We shall see, but first RPi setup and testing with one of the small TRXs. In the beginning just monitoring.
For the old 5 bands (10-15-20-40-80) I have a low hanging dipole, so a simple frequency multiplexer should not be too difficult to construct. I already purchased some toroid cores which should be good for winding the filter coils


Old Electronic Devices

After doing some computer work on low powered computers I decided to look into some older electronic equipment, like old mobile phones, tablet devices and MP3 players (iPods or other players).
Well a the old phones generally work, and can be charged, so the batteries are not quite dead.I will keep one or two for spares, and an older iPhone (32GB) can still be used as an MP3 player. The others are give-aways, as they are old and not very useful for Internet purposes.

Two of the old tablets remained on the boot screen, and I could not recover functions after a few hours. I discard them, and will probably give them to someone who wants to try getting them running. Probably a corrupted system, but I could not restore it, after a search on the Net.

Other old and very slow tablets will likely be given away, if someone wants to play with them, newer ones will probably be set up for different purposes, e.g. a picture viewer, or monitoring often visited websites, e.g. PSK Reporter or propagation monitoring sites, or DX cluster(s).


FT8 Propagation Monitoring.

I have always been interested in monitoring propagation on different bands.
Recently the digital mode FT8 has become very common on bands from 160m to 2m. Since my main interest is in VHF I have set up a few older computers, so I have continuous monitoring (barring the risk of thunderstorms) on 2, 4, 6 and 10m.
On 2, 4 and 6m I can immediately transmit (If I can find the correct mouse ;). On 10m I have continuous monitoring only, but a 5th machine can move around all HF bands and operate the transmitter on 10m as well.