ADALM-PLUTO (new DATV SDR)

[G4GUO]

It could be the 3rd harmonic of the LO mixing with the baseband signal.

I would have thought that might also be overlaid with the 3rd harmonic of
the PA stage.

It would be interesting to see what it looks like on a spectrum analyser.

- Charles

P.S I just set mine to 2 MS/s 1 GHz and then looked at the 3 GHz component
the 3 GHz component is definitely 2 MS/s with an EVM/MER as good as the
fundamental component so I speculate that 10 GHz is the same.

[g8gtz]

Quick test shows 2MS at 3.4 GHz

IMG_3449.JPG (33.5 KiB) Viewed 8857 times

It's there but not very loud at 10 GHz

IMG_3450.JPG (31.84 KiB) Viewed 8857 times

73

Noel

[g0mjw]

That's interesting. What do you get at 5.7 GHz x2 ? Could this spurious signal be filtered and amplified perhaps? Do we now have a 6m to 3cm DATV exciter for £92?

I speculate its a harmonic mixer type effect rather than a third harmonic. Need to be careful not to overload the mixer in the spectrum analyser when checking. A high pass filter (e.g. length of waveguide) would sort that out.

Mike

[G4EWJ]

I would expect to see some combination of harmonics of the modulated output and modulation of the LO harmonic. It would be interesting to see the 10GHz signal at 60dB down.

I tried the second harmonic and while it got carrier and SR lock, it wouldn't fully lock, even though the constellations looked reasonable.

Brian

[MW0LLK]

One slight problem now though Charles - I can't get express to run! I get: Configuration Error "0".

My express board works okay with an archived software version (1.11) using the cfg file copied from my current (1.25p1) install so drivers etc. are okay.

Tonight on GB3TM activity night I used PlutoSDR exclusively as a result - which it handled very well!

I also notice that FEC 5/6 doesn't seem to work with PlutoSDR though all others are okay.

Keep up the good work!

[G8GKQ]

The Portsdown "Ugly" mode uses the 5th harmonic of of a QPSK modulated 87.4 MHz signal to generate 437 MHz QPSK. I'm not sure of the maths of the multiplication of the phase shift, but it certainly works!

Dave, G8GKQ

[G4GUO]

Hi Chris,

Those problems are both fixed in the next release.
I can't release the next release as I am having problems with symbol rates of 4M
and above. I have some questions outstanding on the Analog Devices forum
to do with sample rates and IQ calibration so not much I can do until those are
answered.

- Charles

[G4EWJ]

Charles,

Would it be possible to enable Pluto 'Carrier Only' mode please? It's handy for power setting and antenna peaking.

Brian

[G4GUO]

Of course Brian, added.

All it has done is show up what looks like an 2.3 KHz FM signal on the transmission.
I suspect from PSU noise.

I am looking at calibration at the moment. It seems AD's on chip calibration routines
don't do very much, certainly as far as getting rid of LO leakage due to IQ DC offset errors.

With Express if you do a manual calibration (using the calibration menu) you can get
the LO leakage to drop almost into the noise floor of the spectrum analyser.

- Charles

[G4GUO]

I have had to re-instate the burst of rubbish the transmitter sends out when changing frequency
as that is part of the automatic transmitter calibration routine.

At initialisation the unit does a once only baseband calibration then every time the transmitter
changes frequency by more than 100 MHz it does an RF calibration.

I have also found the attenuator setting seems to affect the LO leakage and unwanted sideband levels.
The best I have seen is -60 dB unwanted sideband suppression and about -50 dB LO leakage.

I am still struggling to get a reliable 4 MS/s, my PC is doing virtually nothing but samples
are still being dropped. Analog Devices claim it can do 10 MS/s BTW.

- Charles