SR2000+ seems to not work

[F1NST-Bernard]

Dave,

I did, without HDMI and touch by USB deconnected.
Herebelow local control at SR333 and SR1500.
Hope this could help.

The receiver antenna is a vertical disconne behind the 437 HB9CV whici explain less power. Thanks again

Bernard

[g0mjw]

I see you are using a sharp tuner with an upconverter. I don't know if the signal levels might be a bit high? Neither of those constellations looks good. I would not describe that 6dB MER as working very well! Maybe there is an RF problem?

Are you sure the converter is working? Maybe try 23cms directly to eliminate that possibility?

Also suggest you try DVB-S rather than auto.

[MN-tech]

The text of these posts and the MiniTioune screen both show the symbol rate in question is 1500. Which symbol rate selection does the R-Pi send to the filter modulator at that setting?
SR2000 would work well but would have too wide a spectrum. That would be indicated by Pins 2 and 4 of J02 being high.
SR1000 likely would filter too much.
Perhaps somebody could try setting SR1500 in their Portsdown and seeing how it behaves for them.

[F1NST-Bernard]

I pursue my investigations, regarding the upconverter, is functionning as on low SR everything are OK. I also try with DVB-S instead as automatic.
It appears something if I switch in QPSKRF mode, SR1500 FEC5/6 and sometime FEC3/4 try to decode but it is very unstable.

So the last alternative is to (again) recheck all the welding and the good state of U23 and following.

Thanks to MN-tech for this question as don't really which SR is active when enter by hand 1500, the ctlfilter script state either <1100 or <2200, the first one will be used for SR1000 and the second for SR1500 but I have not checked in the program the calculation formula which allow to make the good RS chosen.

Thanks all

Bernard

[MN-tech]

If the R-Pi won't send SR1000 to the filter modulator when SR1500 is selected you could temporarily disconnect the wires to pins 2 and 3 leaving only voltage on pin 4 to select SR1000.

[G8GKQ]

Bernard, John

The (correct) SR filter switching is not the problem here. Selection of SR1500 introduces the SR2000 filter into circuit. I have just tested it and it works perfectly.

I think that the next test is for Bernard to disconnect the Raspberry Pi from J02, and connect pin 1 of J02 on the PCB to ground (very important). Then connect pins 3 and 4 to +5v. This will switch the 4MS filter into circuit and allow all SRs to work.

Perhaps you could change the frequency to 1255 MHz to eliminate the up-converter, as you really ought to be getting an MER of 25 or 26 at all SRs. A reading of 6 indicates that something is wrong - even at 333KS.

Dave

Last thought - have you connected Pin 1 of J02 to ground? It is not connected through the board and needs an external wire.

[G8GKQ]

And another thought. What local oscillator are you using? These symptoms could be caused by too much phase noise on the LO.

Dave

[F1NST-Bernard]

Hello all,

I followed your advice and did 2 small but certainely important things. First of all I put in place capacitors C5 an C6 on the LO Filters circuits. In fact I await from Farnell the 22 µf due to be delivered in august and beleived that this was not really important as in front of the regulator I put a 7808 with capacitors. According to data sheet I used 0.1µ tantalum for C5 and 10µ for C6 (I will use 22µ on receipt)
The second point, I checked the various ground and noted that the wires to command the ADF4351 circuit was only CLK,DAT, and LE, the ground from the GPIO interface was missing OUPSSS!
Having remedied to these mistake and at least obtained the following results.

1255 Mhz SR1500 on dummy load and a wire on Titioune as receiver in the shack



437 Mhz 40mW on 437Mhz Antenna HB9CV outside, receiving on disconne also outside . I'm awaiting 7w amplifier from Minikits to finalise



We can say that small default have great wrong results ... Thanks for your kindly help.

Have you any comments/suggestions regarding the results??

Bernard - F1NST

[g0mjw]

Missing the ground connection is not great - but there is probably a ground route via the coax and other boards. I'm not sure if that was the problem as I still see some problems in the constellations.

There is a DC offset which needs trimming out. There also looks to be significant phase jitter on 437MHz. I don't see it on 23cms. Either its a very odd multipath effect, or there is something not entirely right with your local oscillators. You should have four dots and an MER well over 20dB. These oscillators are in the frequency converter and the ADF4351. I suspect the frequency converter because the ADF4351 is clearly OK on 23cms. If you are receiving off air - is there interference?

Try looking at the spectrum of the CW carrier mode at the TX output and after the converter. Ideally with a spectrum analyser but failing that an RTL dongle and SDR Sharp.

I once had a problem like this because an oscillator was too close to a 12V power supply transformer. Other possibilities are ground loops, oscillating LM7808 and LM7805 regulators, using the same power supply for the PI and the AD4351 etc.

Mike

[G8GKQ]

Hi

I think that the odd constellation at 1255 is due to LO leakage, not a DC offset, but I agree that something here is definitely not right. Mike's suggestion of a power supply oscillation or similar seems likely.

You might also check the supply voltage at the Pi (measure it on the GPIO pins) - it could be that you have too much voltage drop in its supply lead. You should see between 5.0 and 5.2 volts at the PI. Nothing lower

Dave.