At 07:55 PM 2/11/97 -0600, Tony Drumm wrote:
>OK, folks. I've seen slightly conflicting info on how to attach the TiCK
>telemetry signal, but I think I can make it work.
>
>However, I do have a question. From what I can tell, the TiCK mod leaves in
>C33 and R18. What purpose do they serve at that point? I don't think they
>are needed for the op-amp. C32 seems somewhat superfluous, too, and the
>different approaches to the mod seem to attach the TiCK audio to one side or
>the other, if I'm reading them correctly.
>
>Any comments?
Yes...I have some. C33 and R18 form a voltage divider with R17, so that
the TiCK audio level is comparable to the signal level from the receiver.
I used a slightly different approach than others, (I seem to do that) in
that I left did the standard trace cut which disconnects R17 from the
output of U4E. I also cut the trace on the "A" side of C32. My R17
is 10Meg, C33 is 0.01uF, R18 is 5.1K, and C32 is 0.1uF. The output
side of C32 is routed directly to the junction of R19, C34, and R20, i.e.,
the summing junction of op amp U5A. I still have too much side tone audio,
but it is tolerable. I still think there is some other coupling going on
via the power supply, ground look, ???? that is making the side tone so
loud. I saw no difference in signal level with R17 at 2.2Meg or 10Meg.
That shouldn't be!! But I haven't had time to dope out what is going on.
Too busy running the rig on the air.
Speaking of that, I worked 2 CA stations tonight about 0000Z, so the
'ol band is doing good again. :-)
72....Jim
Jim Kortge, K8IQY (ex NU8N) | BMHA, NorCal, QRP-L
jokortge@tir.com | __o Cascade 17/40 SSB
Fenton, MI |_`\<, Mizuho 17/40 SSB
.... .. .. . . .. . (*)/(*) . . . . . ..
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