Langstone for QO100

[g4eml]

I agree with Mike's suggestion. It could be another transponder causing interference.
I don't know what sample rate or offset Sdrconsole uses, but it is unlikely to be the same, so the unwanted responses will be different. The Pluto has no input filtering so it will respond to a wide range of signals.
Reducing the gain, adding some attenuation or adding some Rx filtering might all improve things.

Colin.

[Pa3fbx]

Thanks Colin and Mike.

I know the input of the pluto likes a 50Ohm and some attenuation was always advised.
So i already installed 20db attenuator. Keep in mind the cable between lnb and pluto is only 5 meters so i got lots of signal anyhow.

I have not installed extra filtering which is still on my todo list.
I first thought its a noisy power supply or bad 25Mhz reference, but al these are excluded one by one..

I would like someone show his rx screen of the qo100 beacon and say 10kc down...

tbc benno

[radiogareth]

Hi Benno, I've three pictures I can send you, adding a 4G filter helped a lot but off-frequency the S meter did not go down to S0 until I dropped the RF gain down to 32dB. Short cable (12m) from a Bullseye LNB, then into an active splitter, 4G filter, (AF4G Mercury branded) Pluto RX no extra attenuation.
PM me your preferred email and I'll send you the pics for comparison.
Gareth

[g4eml]

Hi Benno,

Your results with the 1m dish appear to be about what I would expect.

Just to mention, for a finer resolution you can display the S-Meter readings in dB instead of S points. Just touch the S-Meter to switch.

I have just done some tests on my Langstone with 1.2M dish. I see a difference of 23dB between the noise floor and the lower beacon. That agrees almost exactly with the values from the Goonhilly WebSDR. 23dB is just under 4 S-points.

I don't know what the FFT bin size is for the Goonhilly WebSDR, Langstone uses 512 points, so at the default 48K spectrum width each bin is about 94Hz.

Reducing the spectrum width from 48K to 6K gives 12Hz bins which shows the expected 9dB reduction in the noise floor. repeating the measurement now shows a difference of 32dB between noise floor and beacon or just over 5 S-Points.

Comparing Langstone to the Goonhilly WebSDR all signals sound just about the same. I listened to a very weak SSB QSO and an extremely weak CW QSO and the all were very similar, possibly slightly easier to read on the Langstone, but that may just be down to the speaker response.

73
Colin

[Pa3fbx]

Thanks Colin,
i will copy your tests.. I think my speaker is also not real good.
Is there an easy way to put the usb headset in the raspberry and use that mic and speaker.
I have used it during setup but now i use the usb audio dongle.. But some kind of selectable audio setup would be super..

will report the results..

Benno

[g4eml]

Hello Benno,

No, at the moment the software only supports one USB audio device. That is a limitation of the GNU radio code. It might be possible to add a second device, but I am not sure how that would cope if only one was present.

There may well be a Linux way of routing the audio to multiple devices but I don't know how to do that.

Colin.