Langstone as a Microwave transverter driver

[g8gtz]

Hi

Now using the Langstone / Portsdown combo as my microwave transverter driver - had QSOs on 5.7, 47 and 76GHz with it and the waterfall just makes things so much easier

I am still having issues with the Pluto crashing into DFU mode and requiring a rebuild but I think this is down to earthing - it's a rev D PCB and they claim to have fixed it...

The big problem I have is radiated noise from the RPi + screen getting into the 2 metre talkback rig. Tin foil and earth bonding helps but may have to end up putting it into a diecast box.

2 feature tweaks would be nice - a transmit power indication such as a not calibrated bouncy bar would be good. And the ability to record audio (or I+Q) would be useful at times.

A great system and I'm currently writing up an article for scatterpoint and one for Radcom - much cheaper than an FT/IC 1234

73's Noel

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Receiving GB3FN beacon on 5760.920

[g4eml]

Hi Noel,

The sensitivity of the Pluto to earth loops seems to be its main shortcoming. It is a pity that the latest version hasn’t fixed that.

The RF noise from the Pi and screen is a problem with Portsdown as well. It interferes with the 2M talkback and almost certainly affects reception on 146.

I will see if I can add a transmit power indication, but it won’t be a simple thing to add. It would involve another output pipe from the GNU Radio code and that might introduce more problems.

I have made a couple of changes to the Langstone code today to fix a bug found by G4FRE and also to improve the handling of the Beacon modes. When operating on SSB the beacon is now sent with a frequency offset of 800Hz. This means the receiving station should be able to hear both the beacon and the SSB voice without having to retune. The beacon can now also be cancelled by pressing the PTT. So if you are sending a beacon for alignment you can just press the PTT and start talking on SSB.

Colin.

[g4eml]

I tried adding the Tx level indication today but ran into problems. I could get either the Tx level or the Rx waterfall working but not both. More investigation needed.

Colin.

[radiogareth]

Rather than having a bouncy bar would not the TX attenuation number be enough? When I'm testing in the garden or with driving amps etc I just leave TX atten on screen and tweak as required. In Noels picture I see he was displaying RX gain. Maybe a facility (like a shift key) to jump up into RX gain and TX attenuation number (i.e. not within the main menu tree) and be able to adjust both on the fly with the rotary encoder and L/R buttons in the way that freq can be changed?
Just a thought....
Gareth

[g8gtz]

Thanks Colin - no problem.

Gareth, not really. You can get into the menu whilst transmitting and adjust the attenuation.

What I was after was some indication of RF going out - I'll work on a simple diode detector on the 1 watt PA and an old fashioned meter

Noel

[g4eml]

My plan was to generate a waterfall from the transmit output in the same way it does for the receiver. In that way it would show your output spectrum and modulation and the existing S meter would indicate output power.
It would not however be an actual measurement of the Pluto’s output, I don’t think that is easily done. It would show the drive level to the Pluto which would then be reduced in the Pluto by the output attenuator setting.

Colin.

[CU2ED]

Hi Colin,

I like your TX plan, indeed I was able to see, yesterday on BATC NET, a small preview of your idea and I loved it ... hope everything goes well
so it can be available very soon

73

Jacinto
cu2ed