[amsat-bb] Can I cross-band my way to L-band BBS?

Greg D. ko6th_greg at hotmail.com
Sat Feb 21 17:03:51 PST 2009

This may be too crazy of an idea, so I should probably ask before I put too much effort into it...

The only 9600 BPS packet capability that I have is with my Kenwood TH-D7A, but the BBS system on AO-51 is currently in mode LU, and now we hear that CO-65 will be doing the same.  I have L-band capability in my Yaesu 736R.  Would it be possible to link the two?

AO-51's downlink is on 70cm; I'd need to use 2m as the link between the radios.  D7 listens on 70cm, and transmits on 2m.  (I believe the D7 can work split band on packet, right?)  The 736 listens on 2m and transmits on 1268.  Since the 736 can't do "cross band repeat", in the traditional sense,
my thought is to use the satellite mode on the 736 and cross-connect
the audio at the data in/out jack and use the VOX on 1268 to key the transmitter.  

I can think of two issues with doing this.  First, is the VOX operation going to be quick enough to get the whole packet through?  I'll probably need to extend the transmit delay to compensate; how long?  Second, is the audio response going to be adequate going in and out of the Data jack?  It's supposed to be right off the demodulator, without any audio shaping, but the rig is unmodified in this area and I thought the 736 didn't do 9600 very well out of the box.  

I've got the 736 hooked to the computer for Doppler tracking; at least that part should work.  Oops, no, not quite; I'd need to modify the PC's Doppler control client so that the 2m side stays static.  Not a big deal.

So, is this worth trying?  (I know, buying a "real" TNC would be a lot easier...)

Greg  KO6TH

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