[amsat-bb] Re: VO-52 Frequency Drift

[i8cvs]

Hi John, K8YSE

I notice that the Dutch Transponder suffers of non linearity and
distorsion probably due to the fact that the AGC of it has not
been designed like the indian transponder but apparently only
using a diode based limiter so that when a strong signal comes
in the distorsion occurs for all stations operating in the passband.

In a separate email I will send to you a mp3 file for a QSO made
between me and IW6OVD using the indian Transponder few
days before it failed and I am sure you will notice the difference
in linearity and quality of modulation with the actual Dutch
Transponder.

It should be very interesting to get some technical explanations
about from William PE1RAH but after the recovery of VO-52
I have not seen any comment from him on AMSA-BB

I have not investigated about the frequency stability of the Dutch
Transponder but I will do.

73" de

i8CVS Domenico
----- Original Message -----
From: "John Papay" <john at papays.com>
To: <amsat-bb at amsat.org>
Sent: Monday, March 26, 2012 5:04 PM
Subject: [amsat-bb] VO-52 Frequency Drift


> VO-52 has been a very loud and easy to work satellite
> since the recovery and change to the Dutch Transponder.
> The CW beacon is very loud and you can usually find an
> image of it elsewhere in the transponder passband.
>
> If you are running full doppler control, you have probably
> noticed that your settings (uplink calibration) have to be
> changed from pass to pass.  The beacon frequency is not constant
> either so I suspect that the frequency source is not very
> stable.  Stability is usually a function of temperature so
> it would appear that the temperature inside the satellite is
> changing due to internal electronics and/or effects from the
> sun.  This would be something that the control team would be
> aware of.  Any feedback from them would be appreciated.
>
> I do not recall that the India Transponder had a similar problem
> but maybe someone else could comment on that.  If it did drift, it
> was only one or two hundred Hz.  Initially the difference between the
> India and Dutch Transponder was about 2KHz.  Now it seems to vary plus
> or minus 500 Hz or so.  Maybe some others can comment on this.
>
> 73,
> John K8YSE
>
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