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11263 MHz - same frequency transponders C4 and C3 comparison
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EUMETSAT have confirmed that the new C3 transponder is in test mode since Friday 2022-11-11 at 15:20. They are also seeing SNR degradation since the switch-on.
Here's a comparison of the existing BAS/HVS-1 (C4 H) and the new HVS-2 (C3 V) transponders, which differ only in the polarisation of the signal. - On the BAS/HVS-1 (C4 H) you can clearly see the switching between the two modes. The spectrum analyser software is scanning in ~6 MHz chunks so the apparent switching times bear no relation to the actual switch which is between all BAS or all HVS-1 for the full spectrum, but it's by chance that the plot is useful in showing the two modes. The out-of-band noise level appears to be around -40 dBm. - On the HVS-2 (new C3 H) plot there does seem to be a slight tilt to the spectrum with higher frequencies providing a little more signal than the lower ones. I am slightly surprised by this. Does anyone else see the same? This also shows with CrazyScan plot (not attached). The out-of-band noise level appears to be around -37 dBm. I don't know why there would be such a difference in noise level. Oh,and before you ask, yes, I would normally use PNG for screenshots, but in this instance the JPEG were under half the size. Comments welcomed! Cheers, David -- SatSignal Software - Quality software for you Web: https://www.satsignal.eu Email: david-taylor@... Twitter: @gm8arv 
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geojohnt@aol.com
David,
Following my post yesterday regarding SNR comparisons between 11.263 V and H - down here I had just over 1 dB difference in SNR between H and V. V being the lower value.
This morning with rain and gales down here I've been seeing V is higher SNR than H by around 0.6 dB.
I can only monitor the SR1 Controller readouts (on a single SR1, switching polarisation via telnet) and can't match your analyser scans.
For example my TP1 SNR clear sky is usually ~ 13.6 dB Power -18 dBm
At 09:23 this morning (with rain and gales) TP1 was 11.3 dB Power -19dBm.
HVS-2 was 11.9 dB Power -21 dBm.
I sent a report to Ops yesterday and will again today with this awful weather.
I might just say that at ~ 22:45 last night (all times in UTC) both TP1 and HVS-2 SNR's were stepping up and down like a yo-yo.
TP1 SNR for a very brief moment went to 14.4 dB.
Regards,
John
-----Original Message-----
From: David J Taylor GM8ARV 🏴 🇪🇺 via groups.io <david-taylor@...> To: MSG-1@groups.io Sent: Tue, 15 Nov 2022 8:33 Subject: [MSG-1] 11263 MHz - same frequency transponders C4 and C3 comparison EUMETSAT have confirmed that the new C3 transponder is in test mode since
Friday 2022-11-11 at 15:20. They are also seeing SNR degradation since the
switch-on.
Here's a comparison of the existing BAS/HVS-1 (C4 H) and the new HVS-2 (C3 V)
transponders, which differ only in the polarisation of the signal.
- On the BAS/HVS-1 (C4 H) you can clearly see the switching between the two
modes. The spectrum analyser software is scanning in ~6 MHz chunks so the
apparent switching times bear no relation to the actual switch which is between
all BAS or all HVS-1 for the full spectrum, but it's by chance that the plot is
useful in showing the two modes. The out-of-band noise level appears to be
around -40 dBm.
- On the HVS-2 (new C3 H) plot there does seem to be a slight tilt to the
spectrum with higher frequencies providing a little more signal than the lower
ones. I am slightly surprised by this. Does anyone else see the same? This
also shows with CrazyScan plot (not attached). The out-of-band noise level
appears to be around -37 dBm.
I don't know why there would be such a difference in noise level.
Oh,and before you ask, yes, I would normally use PNG for screenshots, but in
this instance the JPEG were under half the size.
Comments welcomed!
Cheers,
David
--
SatSignal Software - Quality software for you
Email: david-taylor@...
Twitter: @gm8arv
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