[amsat-bb] Spirit II and ICOM woes continue

["Jeff VanMeter" <jvanmetr@xxxxxxxxxxxxxx>]

Hello All,

I have previously described a problem in using the Spirit II TNC with the 
IC-910H.  In short, I have found that the through put is terrible at best on 
transmit.  I have only once been able to access GO-32 with several tries.  I 
have gotten some info through AO-51, but my uplink rate is poor.

After hearing several suggestions, I finally bought a deviation meter.  When 
running in CAL mode, I checked where I had set the modem output last by ear. 
My deviation was 2.0 KHz.  Not too bad,  but most of the literature suggests 
2.5-3.5 KHz for best results.  So I attempted to increase the drive from the 
modem.  I was able to get the deviation to 2.25 KHz.  Not a lot more.  Now 
the limiter in the IC-910H is preventing me from driving beyond this point. 
After exceeding a certain point of drive , I think .5V peak-to-peak,  the 
transmitter will not transmit.

I suspect others have had this same prolem, but like me were decreasing the 
drive thinking they were overdeviating.

If anyone has a solution, I'd be glad to hear about it.  I would like not to 
have to reinvent the wheel.  My next step will be to put a capacitor in 
series with the output of the TNC incase there is any stray voltave there 
that may be tripping the limiter on the IC-910H.  If this fails I might try 
an audio isolation transformer.

If I can get my scope to work, I'll check the output from the TNC directly 
to see if there is a baseline shift.  I suspect that this is the problem.

Thanks, and I'll keep you posted.

Jeff
KA8HQL 
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