[amsat-bb] EO-79 Transponder frequencies

David G0MRF g0mrf at aol.com
Wed Nov 16 23:30:03 UTC 2016

Hi All.

Hope those of you back from cruising across the Gulf of Mexico had a good time.

Over the past few days I've been trying to determine the transponder frequencies for EO-79 as there are some
differences between published sources and those appearing on the BB

435.047-435.077 MHz LSB
145.935-145.965 MHz USB

However, from observations, there seems to be no downlink below 145.946.
By taking readings at TCA on low elevation passes, which for me is about 20 minutes into the 25 minute schedule.
The transponder appears as follows:

Lower limit is quite well defined at 145.946.  
Upper limit roles off slowly above 970. But 145.971 seems a reasonable limit. Very strong signals are visible to 973 but are heavily attenuated.

Upper limit (for 145.946) = 435.0723
Lower limit (for 145.971) = 435.0473

This suggests the transponder has a nominal bandwidth of 25kHz.
My best guess at a translation frequency is 581.0183MHz

If anyone with some fancy computer control would care to refine these a bit further....I'm sure we would all be grateful.

Many thanks to Ken GW1FKY for providing 'known' signals in the transponder. and Juan LU2DPW for observations from Argentina (when the satellite is much colder)


David  G0MRF

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