[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

AO-10 & PSK possibilities



I sent a few CW "pings" at AO-10 tonight, and listened to the beacon.
There is the usual deep QSB, but the beacon is clearly audible, especially
with a very narrow bandwidth (150 Hz or less on my Timewave DSP-599zx).  My
CW signals were audible on the downlink through more than half of the "spin
cycle."  However, both the transponder and beacon are still FM-ing.  I
measured a frequency variance (with the SPECTROGRAM program) of about 100
Hz on the beacon.  

Note: my 2m downlink antenna is an M^2 14 element crossed yagi--those of
you with 22 elephants have a couple of dB less noise.

When the frequency stabilizes, I'm anxious to try using PSK31 on the bird.
My HF experience with G3PLX's PSK31 program tells me that its AFC can
follow a *slow* drift once locked on.  So PSK31 should be able to cope with
the very slow drift of AO-10 once it's reasonably past perigee.  Right now
the FMing is too much.  

I suspect PSK31 as presently written won't work well on LEO downlinks
either, with the possible exception of RS-13.  The 10-meter downlink has
doppler changes of between approximately 20 and 150 Hz per minute at
elevations from 10 degrees to TCA on a high pass.  I don't know precisely
what PSK's AFC drift limit is.  Has anyone tried PSK on the birds yet?

73 from KD7MW,

--- Peter
/\:     ________     __     =========     ,  ,  ,  ,   ,  ,  |'  ,      ,
 / b   |  |  |  |   |  |   |  |   |  |   |  |  |  |   |  |   |  |  ~|' |
/ b b ,| ,| ,| ,|  ,| ,|  '  ,|   | ,|   |__|__|__|   |__|   |  |   |  |
                                ~'                            ========= 

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home