Q0-100 Web-SDR 198Hz frequency error


Andy G4JNT
 

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




Dave G8GKQ
 

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

 

 

 

Andy

 


Andy G4JNT
 

Actually, highly embarassing co+=up here.
There does seem to be something wrong with my conversion.   Now I've sent up a fully locked uplink as well, Goonhilly is reporting teh correct result and my system is the one in error

At 200Hz out  and quite stable it can't be the LNA locking, the FDM duo is showing locked so it must be the auxilliary downconverter - which is a bit odd 



On Tue, 22 Jun 2021 at 16:19, Dave G8GKQ <dave.g8gkq@...> wrote:

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

 

 

 

Andy

 


Andy G4JNT
 

Nope cancel that.   My system is locked up perfectly - all converters checked..  There really is a discrepancy somewhere

Rx system set to 10489.98300MHz USB.
Local synth set to 10489.985 locked to same reference 
Tone generated in Rx system 2000.0Hz    -  That proves Rx system frequency conversion process

Local 10MHz reference currently running +0.08 parts-per-billion high, based on GPS monitoring of it,  so contributing just 0.8Hz error.  

2400.985 MHz uplink to satellite, locked to the same reference gives received tone on my system  of 1886.7Hz,  Within expected sat conversion error and Doppler range

Goonhilly Web-SDR set to 10489.983, tone is  2081.5Hz
Goonhilly is showing the classic GPSDO wobble of 3 - 5Hz RMS, with excursions to 10Hz so it looks as if it's properly locked.

Don't understand this ...........




On Tue, 22 Jun 2021 at 16:31, Andy Talbot <andy.g4jnt@...> wrote:
Actually, highly embarassing co+=up here.
There does seem to be something wrong with my conversion.   Now I've sent up a fully locked uplink as well, Goonhilly is reporting teh correct result and my system is the one in error

At 200Hz out  and quite stable it can't be the LNA locking, the FDM duo is showing locked so it must be the auxilliary downconverter - which is a bit odd 



On Tue, 22 Jun 2021 at 16:19, Dave G8GKQ <dave.g8gkq@...> wrote:

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

 

 

 

Andy

 


Dave G8GKQ
 

Hi Andy

 

I know that there was a systemic error measured on the WebSDR in the past, but we couldn’t find which part of the system it was in, so have not corrected for it.  Prime suspect is the Octagon LNB which derives its LO from the 25 MHz GPS Ref (a Leo Bodnar dual-output unit).

 

We stopped worrying about it over a year ago.  The WebSDR does the job that it was designed to do.

 

Dave

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Andy G4JNT
Sent: 22 June 2021 17:07
To: UK Microwaves groups.io
Subject: Re: [UKMicrowaves] Q0-100 Web-SDR 198Hz frequency error

 

Nope cancel that.   My system is locked up perfectly - all converters checked..  There really is a discrepancy somewhere

 

Rx system set to 10489.98300MHz USB.

Local synth set to 10489.985 locked to same reference 

Tone generated in Rx system 2000.0Hz    -  That proves Rx system frequency conversion process

 

Local 10MHz reference currently running +0.08 parts-per-billion high, based on GPS monitoring of it,  so contributing just 0.8Hz error.  

 

2400.985 MHz uplink to satellite, locked to the same reference gives received tone on my system  of 1886.7Hz,  Within expected sat conversion error and Doppler range

 

Goonhilly Web-SDR set to 10489.983, tone is  2081.5Hz

Goonhilly is showing the classic GPSDO wobble of 3 - 5Hz RMS, with excursions to 10Hz so it looks as if it's properly locked.

 

Don't understand this ...........

 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 16:31, Andy Talbot <andy.g4jnt@...> wrote:

Actually, highly embarassing co+=up here.

There does seem to be something wrong with my conversion.   Now I've sent up a fully locked uplink as well, Goonhilly is reporting teh correct result and my system is the one in error

 

At 200Hz out  and quite stable it can't be the LNA locking, the FDM duo is showing locked so it must be the auxilliary downconverter - which is a bit odd 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 16:19, Dave G8GKQ <dave.g8gkq@...> wrote:

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

 

 

 

Andy

 


Andy G4JNT
 

There is a systematic 50.00 Hz error in my, and others' 27MHz reference Octagons - the first generation ones.   No one could explain that, but it was very definitely there.   It's taken out in my intermediate conversion.

I've just been systematically going through everything, and confirmed that lower and upper beacons and my locked uplink all generate tones that are 193Hz apart between the Rx here and Goonhilly.   Also they are all in the same direction  wrt. potential Doppler.
So only conclusion is that Goonhilly is out by around 200Hz , yet showing the expected stability consistent with GPS locking

This offset is a bit problematical, as I wanted to do some low power mobile JT9D tests.   As my Rx system is a bit compromised by trees, and is some 8dB down on Goonhilly  wrt. S/N wanted to use the latter.    If that discrepancy was consistent, it would be usable, but over the duration of this test period, the delta has shifted from 200 to 193Hz
So on a several hour drive around could upset the measurement




On Tue, 22 Jun 2021 at 17:15, Dave G8GKQ <dave.g8gkq@...> wrote:

Hi Andy

 

I know that there was a systemic error measured on the WebSDR in the past, but we couldn’t find which part of the system it was in, so have not corrected for it.  Prime suspect is the Octagon LNB which derives its LO from the 25 MHz GPS Ref (a Leo Bodnar dual-output unit).

 

We stopped worrying about it over a year ago.  The WebSDR does the job that it was designed to do.

 

Dave

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Andy G4JNT
Sent: 22 June 2021 17:07
To: UK Microwaves groups.io
Subject: Re: [UKMicrowaves] Q0-100 Web-SDR 198Hz frequency error

 

Nope cancel that.   My system is locked up perfectly - all converters checked..  There really is a discrepancy somewhere

 

Rx system set to 10489.98300MHz USB.

Local synth set to 10489.985 locked to same reference 

Tone generated in Rx system 2000.0Hz    -  That proves Rx system frequency conversion process

 

Local 10MHz reference currently running +0.08 parts-per-billion high, based on GPS monitoring of it,  so contributing just 0.8Hz error.  

 

2400.985 MHz uplink to satellite, locked to the same reference gives received tone on my system  of 1886.7Hz,  Within expected sat conversion error and Doppler range

 

Goonhilly Web-SDR set to 10489.983, tone is  2081.5Hz

Goonhilly is showing the classic GPSDO wobble of 3 - 5Hz RMS, with excursions to 10Hz so it looks as if it's properly locked.

 

Don't understand this ...........

 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 16:31, Andy Talbot <andy.g4jnt@...> wrote:

Actually, highly embarassing co+=up here.

There does seem to be something wrong with my conversion.   Now I've sent up a fully locked uplink as well, Goonhilly is reporting teh correct result and my system is the one in error

 

At 200Hz out  and quite stable it can't be the LNA locking, the FDM duo is showing locked so it must be the auxilliary downconverter - which is a bit odd 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 16:19, Dave G8GKQ <dave.g8gkq@...> wrote:

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

 

 

 

Andy

 


Gary M1EGI
 

Hi Andy,

Could some of this be explained by the satellite itself?

Oscillators used, thermal changes onboard due to activity on the main payload?

Just a thought.


73 Gary M1EGI



On Tue, 22 Jun 2021, 17:48 Andy G4JNT, <andy.g4jnt@...> wrote:
There is a systematic 50.00 Hz error in my, and others' 27MHz reference Octagons - the first generation ones.   No one could explain that, but it was very definitely there.   It's taken out in my intermediate conversion.

I've just been systematically going through everything, and confirmed that lower and upper beacons and my locked uplink all generate tones that are 193Hz apart between the Rx here and Goonhilly.   Also they are all in the same direction  wrt. potential Doppler.
So only conclusion is that Goonhilly is out by around 200Hz , yet showing the expected stability consistent with GPS locking

This offset is a bit problematical, as I wanted to do some low power mobile JT9D tests.   As my Rx system is a bit compromised by trees, and is some 8dB down on Goonhilly  wrt. S/N wanted to use the latter.    If that discrepancy was consistent, it would be usable, but over the duration of this test period, the delta has shifted from 200 to 193Hz
So on a several hour drive around could upset the measurement




On Tue, 22 Jun 2021 at 17:15, Dave G8GKQ <dave.g8gkq@...> wrote:

Hi Andy

 

I know that there was a systemic error measured on the WebSDR in the past, but we couldn’t find which part of the system it was in, so have not corrected for it.  Prime suspect is the Octagon LNB which derives its LO from the 25 MHz GPS Ref (a Leo Bodnar dual-output unit).

 

We stopped worrying about it over a year ago.  The WebSDR does the job that it was designed to do.

 

Dave

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Andy G4JNT
Sent: 22 June 2021 17:07
To: UK Microwaves groups.io
Subject: Re: [UKMicrowaves] Q0-100 Web-SDR 198Hz frequency error

 

Nope cancel that.   My system is locked up perfectly - all converters checked..  There really is a discrepancy somewhere

 

Rx system set to 10489.98300MHz USB.

Local synth set to 10489.985 locked to same reference 

Tone generated in Rx system 2000.0Hz    -  That proves Rx system frequency conversion process

 

Local 10MHz reference currently running +0.08 parts-per-billion high, based on GPS monitoring of it,  so contributing just 0.8Hz error.  

 

2400.985 MHz uplink to satellite, locked to the same reference gives received tone on my system  of 1886.7Hz,  Within expected sat conversion error and Doppler range

 

Goonhilly Web-SDR set to 10489.983, tone is  2081.5Hz

Goonhilly is showing the classic GPSDO wobble of 3 - 5Hz RMS, with excursions to 10Hz so it looks as if it's properly locked.

 

Don't understand this ...........

 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 16:31, Andy Talbot <andy.g4jnt@...> wrote:

Actually, highly embarassing co+=up here.

There does seem to be something wrong with my conversion.   Now I've sent up a fully locked uplink as well, Goonhilly is reporting teh correct result and my system is the one in error

 

At 200Hz out  and quite stable it can't be the LNA locking, the FDM duo is showing locked so it must be the auxilliary downconverter - which is a bit odd 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 16:19, Dave G8GKQ <dave.g8gkq@...> wrote:

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

 

 

 

Andy

 


Andy G4JNT
 

The discrepancy between the two ground stations won't account for that. LO errors on the satellite will cancel out.

When situated close enough together, (and a couple of 100km is close in this sense) the Doppler for each will be the same - Doppler is of the order of 50 - 100Hz, varying on a diurnal cycle.   

I did a test on QO-100 stability shortly after launch  http://g4jnt.com/QO100_Stab.pdf   but back then didn't check for the web SDR settings.




On Tue, 22 Jun 2021 at 18:33, Gary M1EGI <gary.m1egi@...> wrote:
Hi Andy,

Could some of this be explained by the satellite itself?

Oscillators used, thermal changes onboard due to activity on the main payload?

Just a thought.


73 Gary M1EGI



On Tue, 22 Jun 2021, 17:48 Andy G4JNT, <andy.g4jnt@...> wrote:
There is a systematic 50.00 Hz error in my, and others' 27MHz reference Octagons - the first generation ones.   No one could explain that, but it was very definitely there.   It's taken out in my intermediate conversion.

I've just been systematically going through everything, and confirmed that lower and upper beacons and my locked uplink all generate tones that are 193Hz apart between the Rx here and Goonhilly.   Also they are all in the same direction  wrt. potential Doppler.
So only conclusion is that Goonhilly is out by around 200Hz , yet showing the expected stability consistent with GPS locking

This offset is a bit problematical, as I wanted to do some low power mobile JT9D tests.   As my Rx system is a bit compromised by trees, and is some 8dB down on Goonhilly  wrt. S/N wanted to use the latter.    If that discrepancy was consistent, it would be usable, but over the duration of this test period, the delta has shifted from 200 to 193Hz
So on a several hour drive around could upset the measurement




On Tue, 22 Jun 2021 at 17:15, Dave G8GKQ <dave.g8gkq@...> wrote:

Hi Andy

 

I know that there was a systemic error measured on the WebSDR in the past, but we couldn’t find which part of the system it was in, so have not corrected for it.  Prime suspect is the Octagon LNB which derives its LO from the 25 MHz GPS Ref (a Leo Bodnar dual-output unit).

 

We stopped worrying about it over a year ago.  The WebSDR does the job that it was designed to do.

 

Dave

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Andy G4JNT
Sent: 22 June 2021 17:07
To: UK Microwaves groups.io
Subject: Re: [UKMicrowaves] Q0-100 Web-SDR 198Hz frequency error

 

Nope cancel that.   My system is locked up perfectly - all converters checked..  There really is a discrepancy somewhere

 

Rx system set to 10489.98300MHz USB.

Local synth set to 10489.985 locked to same reference 

Tone generated in Rx system 2000.0Hz    -  That proves Rx system frequency conversion process

 

Local 10MHz reference currently running +0.08 parts-per-billion high, based on GPS monitoring of it,  so contributing just 0.8Hz error.  

 

2400.985 MHz uplink to satellite, locked to the same reference gives received tone on my system  of 1886.7Hz,  Within expected sat conversion error and Doppler range

 

Goonhilly Web-SDR set to 10489.983, tone is  2081.5Hz

Goonhilly is showing the classic GPSDO wobble of 3 - 5Hz RMS, with excursions to 10Hz so it looks as if it's properly locked.

 

Don't understand this ...........

 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 16:31, Andy Talbot <andy.g4jnt@...> wrote:

Actually, highly embarassing co+=up here.

There does seem to be something wrong with my conversion.   Now I've sent up a fully locked uplink as well, Goonhilly is reporting teh correct result and my system is the one in error

 

At 200Hz out  and quite stable it can't be the LNA locking, the FDM duo is showing locked so it must be the auxilliary downconverter - which is a bit odd 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 16:19, Dave G8GKQ <dave.g8gkq@...> wrote:

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

 

 

 

Andy

 


KENT BRITAIN
 

Andy, this is funny on so many levels.

Back in my 10 GHz Gunnplexer days my HP Wavemeter was accurate to 5 MHz at XBand.

And for our work that was close enough!    73 Kent

On Tuesday, June 22, 2021, 11:48:12 AM CDT, Andy G4JNT <andy.g4jnt@...> wrote:


There is a systematic 50.00 Hz error in my, and others' 27MHz reference Octagons - the first generation ones.   No one could explain that, but it was very definitely there.   It's taken out in my intermediate conversion.

I've just been systematically going through everything, and confirmed that lower and upper beacons and my locked uplink all generate tones that are 193Hz apart between the Rx here and Goonhilly.   Also they are all in the same direction  wrt. potential Doppler.
So only conclusion is that Goonhilly is out by around 200Hz , yet showing the expected stability consistent with GPS locking

This offset is a bit problematical, as I wanted to do some low power mobile JT9D tests.   As my Rx system is a bit compromised by trees, and is some 8dB down on Goonhilly  wrt. S/N wanted to use the latter.    If that discrepancy was consistent, it would be usable, but over the duration of this test period, the delta has shifted from 200 to 193Hz
So on a several hour drive around could upset the measurement




On Tue, 22 Jun 2021 at 17:15, Dave G8GKQ <dave.g8gkq@...> wrote:

Hi Andy

 

I know that there was a systemic error measured on the WebSDR in the past, but we couldn’t find which part of the system it was in, so have not corrected for it.  Prime suspect is the Octagon LNB which derives its LO from the 25 MHz GPS Ref (a Leo Bodnar dual-output unit).

 

We stopped worrying about it over a year ago.  The WebSDR does the job that it was designed to do.

 

Dave

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Andy G4JNT
Sent: 22 June 2021 17:07
To: UK Microwaves groups.io
Subject: Re: [UKMicrowaves] Q0-100 Web-SDR 198Hz frequency error

 

Nope cancel that.   My system is locked up perfectly - all converters checked..  There really is a discrepancy somewhere

 

Rx system set to 10489.98300MHz USB.

Local synth set to 10489.985 locked to same reference 

Tone generated in Rx system 2000.0Hz    -  That proves Rx system frequency conversion process

 

Local 10MHz reference currently running +0.08 parts-per-billion high, based on GPS monitoring of it,  so contributing just 0.8Hz error.  

 

2400.985 MHz uplink to satellite, locked to the same reference gives received tone on my system  of 1886.7Hz,  Within expected sat conversion error and Doppler range

 

Goonhilly Web-SDR set to 10489.983, tone is  2081.5Hz

Goonhilly is showing the classic GPSDO wobble of 3 - 5Hz RMS, with excursions to 10Hz so it looks as if it's properly locked.

 

Don't understand this ...........

 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 16:31, Andy Talbot <andy.g4jnt@...> wrote:

Actually, highly embarassing co+=up here.

There does seem to be something wrong with my conversion.   Now I've sent up a fully locked uplink as well, Goonhilly is reporting teh correct result and my system is the one in error

 

At 200Hz out  and quite stable it can't be the LNA locking, the FDM duo is showing locked so it must be the auxilliary downconverter - which is a bit odd 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 16:19, Dave G8GKQ <dave.g8gkq@...> wrote:

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

 

 

 

Andy

 


Andy G4JNT
 

Tempus movet super



On Tue, 22 Jun 2021 at 21:08, KENT BRITAIN <WA5VJB@...> wrote:
Andy, this is funny on so many levels.

Back in my 10 GHz Gunnplexer days my HP Wavemeter was accurate to 5 MHz at XBand.

And for our work that was close enough!    73 Kent

On Tuesday, June 22, 2021, 11:48:12 AM CDT, Andy G4JNT <andy.g4jnt@...> wrote:


There is a systematic 50.00 Hz error in my, and others' 27MHz reference Octagons - the first generation ones.   No one could explain that, but it was very definitely there.   It's taken out in my intermediate conversion.

I've just been systematically going through everything, and confirmed that lower and upper beacons and my locked uplink all generate tones that are 193Hz apart between the Rx here and Goonhilly.   Also they are all in the same direction  wrt. potential Doppler.
So only conclusion is that Goonhilly is out by around 200Hz , yet showing the expected stability consistent with GPS locking

This offset is a bit problematical, as I wanted to do some low power mobile JT9D tests.   As my Rx system is a bit compromised by trees, and is some 8dB down on Goonhilly  wrt. S/N wanted to use the latter.    If that discrepancy was consistent, it would be usable, but over the duration of this test period, the delta has shifted from 200 to 193Hz
So on a several hour drive around could upset the measurement




On Tue, 22 Jun 2021 at 17:15, Dave G8GKQ <dave.g8gkq@...> wrote:

Hi Andy

 

I know that there was a systemic error measured on the WebSDR in the past, but we couldn’t find which part of the system it was in, so have not corrected for it.  Prime suspect is the Octagon LNB which derives its LO from the 25 MHz GPS Ref (a Leo Bodnar dual-output unit).

 

We stopped worrying about it over a year ago.  The WebSDR does the job that it was designed to do.

 

Dave

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Andy G4JNT
Sent: 22 June 2021 17:07
To: UK Microwaves groups.io
Subject: Re: [UKMicrowaves] Q0-100 Web-SDR 198Hz frequency error

 

Nope cancel that.   My system is locked up perfectly - all converters checked..  There really is a discrepancy somewhere

 

Rx system set to 10489.98300MHz USB.

Local synth set to 10489.985 locked to same reference 

Tone generated in Rx system 2000.0Hz    -  That proves Rx system frequency conversion process

 

Local 10MHz reference currently running +0.08 parts-per-billion high, based on GPS monitoring of it,  so contributing just 0.8Hz error.  

 

2400.985 MHz uplink to satellite, locked to the same reference gives received tone on my system  of 1886.7Hz,  Within expected sat conversion error and Doppler range

 

Goonhilly Web-SDR set to 10489.983, tone is  2081.5Hz

Goonhilly is showing the classic GPSDO wobble of 3 - 5Hz RMS, with excursions to 10Hz so it looks as if it's properly locked.

 

Don't understand this ...........

 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 16:31, Andy Talbot <andy.g4jnt@...> wrote:

Actually, highly embarassing co+=up here.

There does seem to be something wrong with my conversion.   Now I've sent up a fully locked uplink as well, Goonhilly is reporting teh correct result and my system is the one in error

 

At 200Hz out  and quite stable it can't be the LNA locking, the FDM duo is showing locked so it must be the auxilliary downconverter - which is a bit odd 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 16:19, Dave G8GKQ <dave.g8gkq@...> wrote:

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

 

 

 

Andy

 


Dave_G0WBX
 

WRT:

From: Gary M1EGI
Date: Tue, 22 Jun 2021 10:33:22 PDT

Hi Andy,

Could some of this be explained by the satellite itself?

Oscillators used, thermal changes onboard due to activity on the main payload?

Just a thought.


Plus the bird itself is not in a true fixed point (WRT the ground stations).

If it's part of a cluster in particular it will move around, I think in a 24 hour cycle.

What does the unexpected offset show 12 hours later, if some 200Hz the other way, maybe that's the cause?

This was explained to me some years ago, by one of the site guys we worked with, when involved with a new DBS uplink install that we were providing the TX PA's for.   But I don't remember the sort of figures he illustrated things with, but the frequencies used were in the 12 GHz area.

(That, as a result of a question I asked, relating to why the antenna positioners kept whirring every few minutes, if the satellite was in a "geostationary" orbit.   That resulted in a good 45 minutes very interesting diversion from amplifier problems, and a visit to one other much older uplink facility on the same site, to see a chart recorder output.)

73.

Dave G8KBV

 



-- 
Created on and sent from a Unix like PC running and using free and open source software:


Andy G4JNT
 

As mentioned yesterday, I measured this Doppler a while back and you can read it at http://g4jnt.com/QO100_Stab.pdf   but that is not the issue here.

The discrepancy spotted yesterday is between my FULLY LOCKED system  and the GOONHILLY Web SDR.
I see I hadn't actually measured the Goonhilly accuracy back in those tests of 2019, that was all about satellite and the ground station beacon's stability.

Will do some more tests before too long..



On Wed, 23 Jun 2021 at 13:25, Dave_G0WBX via groups.io <g8kbvdave=googlemail.com@groups.io> wrote:

WRT:

From: Gary M1EGI
Date: Tue, 22 Jun 2021 10:33:22 PDT

Hi Andy,

Could some of this be explained by the satellite itself?

Oscillators used, thermal changes onboard due to activity on the main payload?

Just a thought.


Plus the bird itself is not in a true fixed point (WRT the ground stations).

If it's part of a cluster in particular it will move around, I think in a 24 hour cycle.

What does the unexpected offset show 12 hours later, if some 200Hz the other way, maybe that's the cause?

This was explained to me some years ago, by one of the site guys we worked with, when involved with a new DBS uplink install that we were providing the TX PA's for.   But I don't remember the sort of figures he illustrated things with, but the frequencies used were in the 12 GHz area.

(That, as a result of a question I asked, relating to why the antenna positioners kept whirring every few minutes, if the satellite was in a "geostationary" orbit.   That resulted in a good 45 minutes very interesting diversion from amplifier problems, and a visit to one other much older uplink facility on the same site, to see a chart recorder output.)

73.

Dave G8KBV

 



-- 
Created on and sent from a Unix like PC running and using free and open source software:


Andy G4JNT
 

The same discrepancy of 190Hz is - to within a couple of Hz - there today as well.
Looking at the block diagram of the WebSDR I see they use an Airspy locked to the same GPSDO, but does anyone know for certain how the Airspy interprets the tuning information it is sent?

The FDM-Dup used at my end, when set to USB the 'dial' frequency is that of the suppressed carrier, or a zero frequency tone.
Is this the same setting used on the Airspy?
Could there be an offset introduced somewhere in the setting chain?   The frequency setting of GH appears to be  in 30Hz increments, but rounding to something else.  IN all cases, I used the actual value showing on the display (shown in kHz)

Comparing the two beacon signals to my (all locked) uplink, they are within 1Hz of each other when using both my downlink and Goonhilly.   SO the beacon signals can still be used as reliable frequency offset indicators to Hz accuracy.

BUT, the keying of the upper and lower beacons  takes a bit of interpreting as to which tone is which.

For CW listening purposes both key in the same direction, rest/carrier  and key down are on the lower of the two tone frequencies.    Key up is 400Hz above that.   (The opposite to the standard defined for terrestrial beacon keying, I think)
On the lower beacon at 10489.500 the lowest frequency, is the reference 10489.50000,   and key up is the higher freq, moving into the passband
But
On the higher beacon, the carrier /key down is 400Hz below the edge of the passband and the key up higher tone is the one that defines teh passband edge at 10490.000000MHz


Andy


On Wed, 23 Jun 2021 at 13:31, Andy Talbot <andy.g4jnt@...> wrote:
As mentioned yesterday, I measured this Doppler a while back and you can read it at http://g4jnt.com/QO100_Stab.pdf   but that is not the issue here.

The discrepancy spotted yesterday is between my FULLY LOCKED system  and the GOONHILLY Web SDR.
I see I hadn't actually measured the Goonhilly accuracy back in those tests of 2019, that was all about satellite and the ground station beacon's stability.

Will do some more tests before too long..



On Wed, 23 Jun 2021 at 13:25, Dave_G0WBX via groups.io <g8kbvdave=googlemail.com@groups.io> wrote:

WRT:

From: Gary M1EGI
Date: Tue, 22 Jun 2021 10:33:22 PDT

Hi Andy,

Could some of this be explained by the satellite itself?

Oscillators used, thermal changes onboard due to activity on the main payload?

Just a thought.


Plus the bird itself is not in a true fixed point (WRT the ground stations).

If it's part of a cluster in particular it will move around, I think in a 24 hour cycle.

What does the unexpected offset show 12 hours later, if some 200Hz the other way, maybe that's the cause?

This was explained to me some years ago, by one of the site guys we worked with, when involved with a new DBS uplink install that we were providing the TX PA's for.   But I don't remember the sort of figures he illustrated things with, but the frequencies used were in the 12 GHz area.

(That, as a result of a question I asked, relating to why the antenna positioners kept whirring every few minutes, if the satellite was in a "geostationary" orbit.   That resulted in a good 45 minutes very interesting diversion from amplifier problems, and a visit to one other much older uplink facility on the same site, to see a chart recorder output.)

73.

Dave G8KBV

 



-- 
Created on and sent from a Unix like PC running and using free and open source software:


DD1US
 

Hi Andy,

 

as far as I know the Airspy does have a “ppm” setting to compensate errors in the internal osciallator.

 

I am not sure, but maybe you have to set that value to zero when using an external reference !?

 

Kind regards

 

Matthias

 

www.dd1us.de

 

 

Von: UKMicrowaves@groups.io <UKMicrowaves@groups.io> Im Auftrag von Andy G4JNT
Gesendet: Mittwoch, 23. Juni 2021 16:59
An: UK Microwaves groups.io <UKMicrowaves@groups.io>
Betreff: Re: [UKMicrowaves] Q0-100 Web-SDR 198Hz frequency error

 

The same discrepancy of 190Hz is - to within a couple of Hz - there today as well.

Looking at the block diagram of the WebSDR I see they use an Airspy locked to the same GPSDO, but does anyone know for certain how the Airspy interprets the tuning information it is sent?

 

The FDM-Dup used at my end, when set to USB the 'dial' frequency is that of the suppressed carrier, or a zero frequency tone.

Is this the same setting used on the Airspy?

Could there be an offset introduced somewhere in the setting chain?   The frequency setting of GH appears to be  in 30Hz increments, but rounding to something else.  IN all cases, I used the actual value showing on the display (shown in kHz)

 

Comparing the two beacon signals to my (all locked) uplink, they are within 1Hz of each other when using both my downlink and Goonhilly.   SO the beacon signals can still be used as reliable frequency offset indicators to Hz accuracy.

 

BUT, the keying of the upper and lower beacons  takes a bit of interpreting as to which tone is which.

 

For CW listening purposes both key in the same direction, rest/carrier  and key down are on the lower of the two tone frequencies.    Key up is 400Hz above that.   (The opposite to the standard defined for terrestrial beacon keying, I think)

On the lower beacon at 10489.500 the lowest frequency, is the reference 10489.50000,   and key up is the higher freq, moving into the passband

But

On the higher beacon, the carrier /key down is 400Hz below the edge of the passband and the key up higher tone is the one that defines teh passband edge at 10490.000000MHz

 

 

Andy

 

 

On Wed, 23 Jun 2021 at 13:31, Andy Talbot <andy.g4jnt@...> wrote:

As mentioned yesterday, I measured this Doppler a while back and you can read it at http://g4jnt.com/QO100_Stab.pdf   but that is not the issue here.

 

The discrepancy spotted yesterday is between my FULLY LOCKED system  and the GOONHILLY Web SDR.

I see I hadn't actually measured the Goonhilly accuracy back in those tests of 2019, that was all about satellite and the ground station beacon's stability.

 

Will do some more tests before too long..

 

Andy

 

 

 

On Wed, 23 Jun 2021 at 13:25, Dave_G0WBX via groups.io <g8kbvdave=googlemail.com@groups.io> wrote:

WRT:

From: Gary M1EGI
Date: Tue, 22 Jun 2021 10:33:22 PDT

Hi Andy,

 

Could some of this be explained by the satellite itself?

 

Oscillators used, thermal changes onboard due to activity on the main payload?

 

Just a thought.

 


Plus the bird itself is not in a true fixed point (WRT the ground stations).

 

If it's part of a cluster in particular it will move around, I think in a 24 hour cycle.

 

What does the unexpected offset show 12 hours later, if some 200Hz the other way, maybe that's the cause?

 

This was explained to me some years ago, by one of the site guys we worked with, when involved with a new DBS uplink install that we were providing the TX PA's for.   But I don't remember the sort of figures he illustrated things with, but the frequencies used were in the 12 GHz area.

 

(That, as a result of a question I asked, relating to why the antenna positioners kept whirring every few minutes, if the satellite was in a "geostationary" orbit.   That resulted in a good 45 minutes very interesting diversion from amplifier problems, and a visit to one other much older uplink facility on the same site, to see a chart recorder output.)

 

73.

 

Dave G8KBV

 

 

 

 

 

-- 
Created on and sent from a Unix like PC running and using free and open source software:
 


Simon Brown
 

Andy,

 

I believe the beacons are all sent from either AMSAT-DL or the hams in QATAR, not generated on the satellite so this introduces another possible (but unlikely) source of error.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of Andy G4JNT
Sent: 22 June 2021 16:09
To: UK Microwaves groups.io <ukmicrowaves@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

 

 

 


Simon Brown
 

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

 

 

 


Andy G4JNT
 

Yes indeed.  They are uplimnked from DK land, and use. I think, a Rubidium or GPS locked source.   So their frequency accuracy can be relied on for a few Hz.   
The error in the satellite appears to amount to around 100Hz, but without doing a full 24 hour measurement to remove Doppler, (in the absence of exact ephemeris for calculating it) the two can't be separated and the satellite LO element isolated.

The GH WebSDR is definitely 190Hz or so out




On Wed, 23 Jun 2021 at 20:04, Simon Brown <simon@...> wrote:

Andy,

 

I believe the beacons are all sent from either AMSAT-DL or the hams in QATAR, not generated on the satellite so this introduces another possible (but unlikely) source of error.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of Andy G4JNT
Sent: 22 June 2021 16:09
To: UK Microwaves groups.io <ukmicrowaves@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

 

 

 


Andy G4JNT
 

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

 

 

 


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

 

 

 


Dave G8GKQ
 

Thanks Simon

 

When Andy first mentioned the problem, I thought that the GPSDO had lost lock again, like it did a few months back before Phil replaced the aerial cable.  However, it appears to be in lock.  I don’t think that there is anything that needs a hardware fix.  The WebSDR was not built to have absolute frequency accuracy, but I believe that it would have, were it not for the systemic frequency error that Andy has identified.

 

When the WebSDR first went live, there was a lot of investigation into this frequency error.  Andy may be able to get more information about it by asking on the AMSAT-DL QO-100 chat and forums.  I did not see it as important at the time, so do not remember the details.

 

The narrow band beacons are uploaded from Bochum in Germany; the Wideband beacon comes from the SCC in Qatar.

 

All the code for the Wideband and Narrowband SDRs are on the BATC Github site.  https://github.com/BritishAmateurTelevisionClub  Phil does have remote access to the server, but as it has run reliably for 2 years with only security updates, we would be very reluctant to make unnecessary changes.

 

Dave, G8GKQ

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Simon Brown
Sent: 23 June 2021 20:08
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Q0-100 Web-SDR 198Hz frequency error

 

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

 

 

 

Andy