Langstone for QO100

[arthur21]

Problem with the SAT operation for QO100.
I have set up Langstone V2 as per the Wiki instructions. The SAT is displayed at the top of the screen.
The RX works perfectly, but when TX is selected there is a problem.
The TX will transmit a carrier on the correct frequency when in FM mode but the carrier cannot be modulated and no SSB O/P
The Langstone works correctly in all modes when SAT is not displayed.

73 Arthur G4CPE

[g4eml]

My Langstone is out of action at the moment so I can't check it for a few days.

One thought, when you are in Sat mode the spectrum display may not display the transmitted signal like it does in normal operation. That is because it is operating split frequency duplex. Are you sure it is not transmitting?


Colin G4EML.

[arthur21]

Hi Colin
I have checked again this morning and I can confirm it will not transmit in SSB mode and only an unmodulated carrier in fm mode.
The setup will put a good signal into QO100 in a simplex mode at 2GHz and I can receive on the web SDR for the downlink.
73 Arthur
G4CPE

[g4eml]

Are you using Langstone V1 or V2?
Pluto or Lime?

I have just checked with Langstone V2 + Pluto and it is working OK here.


Colin.

[arthur21]

Hi Colin
I have tried both V1 and V2 with the same results. The Langstone is now V2 and the SDR is a Pluto on a Portsdown 4 all the latest updates have been installed. Only the SAT mode has a problem all simplex modes work ok. I do have a Lime installed on my Portsdown 2020 I could remove it and try on the Portsdown 4 if you think that is worth trying.
Arthur
G4CPE

[g4eml]

Hello Arthur,

I don't understand what is happening on your system. I have tested my Langstone V2 with Pluto and it is transmitting fine in Sat mode.

There is no point in you trying the Lime.

Can you double check the Tx Offset setting. It should show you the actual 2.4GHz transmit frequency. Make sure that is correct and it matches the frequency you are using when testing in normal simplex mode.

All of the transmit modulation is handled by the GNU radio module, and the program uses it exactly the same in normal and in sat mode, so I am at a loss as to why it is not working for you.

Are you using the recommended white USB audio adaptor? In sat duplex mode it has to input from the microphone and output to the speaker at the same time. I suppose it is possible that for some reason that is not working.

Colin.

[arthur21]

Hello Colin

Success it was indeed a problem with the audio dongle, it was the recommended device but on an extension usb cable.
I removed the 1m long cable and plugged the device direct into the Rpi4 and it worked in Sat mode.
The same dongle has worked in the simplex mode with the extension cable for a fair time without a problem.
Thanks for pointing me in the right direction Colin.

73 Arthur
G4CPE

[g4eml]

Hi Arthur,

That's good news. It sounds like the cable might be slowing down the data transfer rate to the point that the dongle could only transfer audio in one direction. That's strange because USB should be OK with a 1M cable. Maybe a better quality cable would work OK.

73
Colin.

[Pa3fbx]

Hi, I am using the qo100 on the langstone witch is perfect.
But i find receiving a real issue.
I am using a 60cm dish and the difference between the noise and the beacon is 1s point.
If i use the same dish with the same pluto on a sdrconsole system its mutch better understandable...
and more snr (30 db snr or so)
Even on my 1 meter dish i get 3 s point between beacon and ground noise..

On VHF and UHF it seems reasonable..
but on qo100 is very margin able..

Any idea how to improve..

benno

[g0mjw]

I wonder if your LNB is picking up other transponders and the Pluto is being overloaded or there is an image of a wideband transponder on top of it. If so, reducing the gain may help. I have noticed SDR Console does a much better job than most radios do, but not that much better.

Mike