Help please, funny signal from Portsdown 4
Posted: Thu Apr 28, 2022 8:25 pm
I find myself in need of help please!
I just erected a new dish and have it set up and hearing narrow and wide band signals OK. I am using SDR Console for the narrow band SSB. Both RX and TX, to a Pluto via LAN / USB, with the Pluto at the dish. All worked well with my old dish, albeit a rather weak DATV signal out.
The Pluto feeds an AD pre amp via a small attenuator (10dB from memory) and this in turn feeds a 20W SG Labs amp. The SG Lab amp feeds a POTY at the dish via about 12 feet of LM400.
I was initially able to see my tone and tune signals from SDR Console on Goonhilly and they looked fine. I then tried to send a test card from my PD4 and watched for the signal on both my MiniTiouner and on the web quick tune software. I was alarmed to see 2 seconds of a normal signal then it broke up and showed not as 333 kS/s but as 1500 and then 2000 at a low level. I didn't want to spend long sending iffy signals, but using 250 kS/s did the same. 2 seconds of OK, then break up and bizarre signals being received both here and at Goonhilly on the Quick Tune display.
I now cannot send anything from SDR Console via Tune or Tone that is received at Goonhilly.
I brought my Pluto into the house and also the Leo Bodnar GPS set up that locks its LO to 40 MHz instead of an xtal. I don't have a spectrum analyser that goes to 2400 MHz, mine stops at about 1200 MHz. I think.
I do have one of those tiny radio control model power meters and it seemed the Pluto was giving its normal 10 dB when SDR Console was commanded to send a tone or tune signal/ It responded to my SSB voice into the microphone, too.
I put it all back in the box outside and tried the AD preamp direct into the POTY feed co-ax. With my smaller dish I used to be able to have a QSO via SSB to the satellite, albeit not a strong signal, just with the preamp to the POTY. Now I see nothing on Goonhilly...
What I have changed: The dish, the co-ax feeder to the POTY, (McGill Microwave professionally made up LMR-400 and terminated in male SMA's each end by them. POTY is as before and appears undamaged.
The PA is getting power, but I haven't yet measured current draw in TX. The pre amp is getting power.
My suspicions: Not the dish it seems to receive OK. Maybe the brand new co-ax feeder to the POTY is faulty? Maybe the pre amp is kaput? Could I add a 100 dB attenuator and carefully ramp Pluto output up and look at it with my little power meter? Maybe the PA is kaput? Hope not, SG Labs always seem to be behind with orders...
I also have no way I can think of to knowing if the Pluto is outputting a rubbish signal, I reloaded the firmware that's always worked and correct for the PD4. It made no difference. PD4 Pluto menu shows correct IP address, LO frequency, both cores enabled and extended frequency enabled. I have had to reload the boot firmware or whatever it's called before now, but from memory the Pluto was doing sod all and obviously very unwell in order to need that doing. Is there mileage in doing that again?
Here are screenshots of what to me looks like the initial two seconds of OK signal, then one of the less spattery bizarre changes after two seconds. Reducing input power to the Pluto from 0 dBm to -15 resulted in no signal received here or at Goonhilly.
All and any help or advice much appreciated, thanks.
I just erected a new dish and have it set up and hearing narrow and wide band signals OK. I am using SDR Console for the narrow band SSB. Both RX and TX, to a Pluto via LAN / USB, with the Pluto at the dish. All worked well with my old dish, albeit a rather weak DATV signal out.
The Pluto feeds an AD pre amp via a small attenuator (10dB from memory) and this in turn feeds a 20W SG Labs amp. The SG Lab amp feeds a POTY at the dish via about 12 feet of LM400.
I was initially able to see my tone and tune signals from SDR Console on Goonhilly and they looked fine. I then tried to send a test card from my PD4 and watched for the signal on both my MiniTiouner and on the web quick tune software. I was alarmed to see 2 seconds of a normal signal then it broke up and showed not as 333 kS/s but as 1500 and then 2000 at a low level. I didn't want to spend long sending iffy signals, but using 250 kS/s did the same. 2 seconds of OK, then break up and bizarre signals being received both here and at Goonhilly on the Quick Tune display.
I now cannot send anything from SDR Console via Tune or Tone that is received at Goonhilly.
I brought my Pluto into the house and also the Leo Bodnar GPS set up that locks its LO to 40 MHz instead of an xtal. I don't have a spectrum analyser that goes to 2400 MHz, mine stops at about 1200 MHz. I think.
I do have one of those tiny radio control model power meters and it seemed the Pluto was giving its normal 10 dB when SDR Console was commanded to send a tone or tune signal/ It responded to my SSB voice into the microphone, too.
I put it all back in the box outside and tried the AD preamp direct into the POTY feed co-ax. With my smaller dish I used to be able to have a QSO via SSB to the satellite, albeit not a strong signal, just with the preamp to the POTY. Now I see nothing on Goonhilly...
What I have changed: The dish, the co-ax feeder to the POTY, (McGill Microwave professionally made up LMR-400 and terminated in male SMA's each end by them. POTY is as before and appears undamaged.
The PA is getting power, but I haven't yet measured current draw in TX. The pre amp is getting power.
My suspicions: Not the dish it seems to receive OK. Maybe the brand new co-ax feeder to the POTY is faulty? Maybe the pre amp is kaput? Could I add a 100 dB attenuator and carefully ramp Pluto output up and look at it with my little power meter? Maybe the PA is kaput? Hope not, SG Labs always seem to be behind with orders...
I also have no way I can think of to knowing if the Pluto is outputting a rubbish signal, I reloaded the firmware that's always worked and correct for the PD4. It made no difference. PD4 Pluto menu shows correct IP address, LO frequency, both cores enabled and extended frequency enabled. I have had to reload the boot firmware or whatever it's called before now, but from memory the Pluto was doing sod all and obviously very unwell in order to need that doing. Is there mileage in doing that again?
Here are screenshots of what to me looks like the initial two seconds of OK signal, then one of the less spattery bizarre changes after two seconds. Reducing input power to the Pluto from 0 dBm to -15 resulted in no signal received here or at Goonhilly.
All and any help or advice much appreciated, thanks.