[amsat-bb] Signal every 3 khz on FO 29 this morning

Ronald G. Parsons w5rkn at w5rkn.com
Tue Nov 8 20:28:37 UTC 2016

On further investigation, I now believe the signals every 3 kHz noted on the previous posts are not generated on board FO-29 but are possibly from a terrestrial source not tracking Doppler shift properly or perhaps from another satellite whose output frequency corresponds to the input frequency of FO-29. For example AO-85 has an output frequency of 145.980 MHz corresponding to an FO-20 output frequency of 435.820 MHz (plus or minus transponder frequency errors).

As can be seen on the annotated waterfall spectrum from the 7 November pass over Texas around 1700Z


the FO-29 Beacon Doppler curve does not match the unknown signal’s Doppler curve. Also the FM signals in the lower part of the FO-29 passband have the same or very similar Doppler curve as the unknown signal.

Note that the frequency numbers along the upper edge of the waterfall are frequencies as received by my receiver. The frequency noted near the top of the screen shot, 435,852.200 MHz, corresponds to the frequency “at the satellite” of the yellow tuning indicator.

A similar appearance of FM signals was noted today, 8 Nov around 1600Z. Note the Doppler shift of the FM signals does not match that of FO-29. 


On 8 Nov, AO-85 was near FO-29 at the time of the pass, but that was not the case on 7 Nov.


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