Being in LEO orbits, can current day satellites use GPS disciplined oscillator (GPSDO)? They are still below the GEO orbit and should technically be able to receive GPS signals, but for the fact that they are moving very fast. Asking just out of curiosity.

73 de Jon, VU2JO

On Sat, Sep 14, 2024 at 10:30 PM graham shirville via AMSAT-BB <amsat-bb@amsat.org> wrote:

Hi John,

I am not sure if you have received any other answer but…

AO73 has been operating in full time 24/7 transponder on mode for some time now.

The telemetry is also transmitted at low power at the same time on the nominal 145.935 MHz.

The nominal transponder frequencies remain unchanged:
Uplink: 435.150 – 435.130 MHz LSB (Inverting)
Downlink: 145.950 – 145.970 MHz USB

But these do drift a for Hz depending upon the on board temperature – back in the day, perhaps twelve years ago, the design of the oscillators was a compromise between stability and power consumption.

JO97, being a more recent design, does not have this “feature”.

73

Graham G3VZV






From: JOHN GEIGER via AMSAT-BB <amsat-bb@amsat.org>
Sent: Friday, September 13, 2024 7:02 PM
To: amsat-bb <amsat-bb@amsat.org>
Subject: [AMSAT-BB] AO-73 question

Great to see that AO-73 has been QRV again.  I seem to remember seeing somewhere that it has shifted frequency somewhat from the published frequencies.  Is this correct?  What are the current uplink and downlink passbands for it?

73 John AF5CC

Sent using {0}




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