Re: Q0-100 Web-SDR 198Hz frequency error


Andy G4JNT
 

A thought just struck:
'Orbitron'  gives the uplink and downlink Doppler shifts.    Total observed on the beacons will be the sum of these.



On Wed, 23 Jun 2021 at 20:13, Andy Talbot <andy.g4jnt@...> wrote:
If it's a constant offset - or at least one that only varies a few Hz - it's not an issue and can just be taken out in calibration.   And I did some testing of it today at different settings.  All show the same error so it's just a case of doing it a few more times to confirm.

Bearing in mind it's directly locked to a GPSDO, there is an inherent short term stability / wobble on it, anyway, of a few Hz RMS with rapid excursions of 10Hz seen.


On Wed, 23 Jun 2021 at 20:07, Simon Brown <simon@...> wrote:

Dave,

 

If it’s something that simple couldn’t a local ham help – I’m thinking about Robin M0RRX who lives close to the site. I see the dishes from my garden – quite close but a heck of a trek to get around the Helford passage.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of Dave G8GKQ
Sent: 22 June 2021 16:20
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Q0-100 Web-SDR 198Hz frequency error

 

Hi Andy

 

The GHY WebSDR was never intended to be a frequency reference, just something to enable a wider audience to monitor the transponder.

 

I think that it is GPS locked (stable, but not absolutely correct) at the moment, but we have had some recent issues with the GPS [antenna cable].  Unfortunately, site access is difficult at present, and it always means an expensive overnight stay.

 

Dave, G8GKQ

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Andy G4JNT
Sent: 22 June 2021 16:09
To: UK Microwaves groups.io
Subject: [UKMicrowaves] Q0-100 Web-SDR 198Hz frequency error

 

Just checked teh Goonhilly Web-SDR and there is close to 200Hz discrepancy in the tone freq between my fully locked receiving system and it

 

(At 1504z, 22 June 2021) WebSDR tuned to 10489998.00, and the lower keyed tone of the upper beacon comes out at 1681Hz

 

On my system set at the same tuning point, the tone is 1485Hz

 

If I generate a local signal at 10490MHz from a separate synth the resulting tone is 2000.00Hz as expected.

 

Conclusion - Goonhilly Web-SDR  has a frequency locking error

 

 

 

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