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Re: VO 52 Newbie Help Request




What I do is to set my rig to where things would be without any Doppler shift, then adjust the higher band (the uplink in this case) for Doppler, and it gets me pretty close.  Mid-band on VO-52's transponder is 435.250 LSB up, and 145.900 USB down; that's what you'd use when the satellite is exactly mid-way in the pass, when it's relative velocity with respect to you is zero.  But at the beginning of a pass, it's moving rapidly towards you, so you need to adjust.  For 70cm, that's about 10 kHz, and because it's coming towards you, you need to go LOWER in frequency to compensate for the upward shift due to Doppler.  So, I start out with my receive side at 145.900, and the transmit side at 435.250, and it's pretty close.  Send a few dits in CW mode, moving UP to find zero-beat, and switch to LSB.  On my Yaesu 736R I can then select the Reverse Tracking satellite mode, and move around the passband looking for someone else calling CQ, or just stay there any talk to myself for the entire pass, like I did last night when nobody else seemed to be on :-(.

Once you find yourself, you will still need to compensate periodically (no, make that continually) for Doppler.  It's best to leave the lower band alone, and just tune the upper band (the uplink for VO-52), unless you can computer control both of them.

If I recall, for RS-10 I would set my downlink to mid-band on 10 meters, and the same on the uplink, and then tune UP from there on the uplink until I found myself.  I know that seems to contradict what I just wrote above, but I think it's partly because Doppler shift isn't as bad on 2 meters, and partly because VO-52 has an inverting transponder, where RS-10 was non-inverting.

Anybody have the mathematics to support this?

Greg  KO6TH


----------------------------------------
> From: flesnick@tbaytel.net
> To: mm3ycg@btinternet.com; amsat-bb@amsat.org
> Date: Sun, 2 Nov 2008 17:27:56 -0500
> Subject: [amsat-bb] Re: VO 52  Newbie Help Request
> 
> I did a google search today for a list of frequencies that I could enter
> into both my 817 and 857 for AOS thru to LOS for AO-7....Not sure when I am
> calling on a frequency where to listen for a call back....
> I remember playing years ago when I first started radio with the Russian
> sats on 10/15...I think RS11 and 12.......and finding the person calling you
> when calling CQ....
> 
> 
> Good luck, I need help as well..
> 
> Fred
> VE3FAL
> 
> -----Original Message-----
> From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On
> Behalf Of Callum Graham
> Sent: Sunday, November 02, 2008 5:21 PM
> To: amsat-bb@amsat.org
> Subject: [amsat-bb] VO 52 Newbie Help Request
> 
> Hello all. I have just started out in SSB satellites and I have been unable
> to have a QSO  through any yet. I can always find the downlink frequency but
> I can never find the uplink frequency. Is there any particular or easy way
> of tuning in the uplink frequency quick enough before the Doppler moves off
> frequency on the downlink. I'm using a Yaesu FT847 with a collinear antenna.
> Ive been searching everywhere but have not found out any answers yet.....any
> help would be appreciated.! 73 de MM3YCG.
> _______________________________________________
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> 
> _______________________________________________
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