From Newsgroup: alt.ham-radio.packet
Hi Frank
Interesting the number of useless answers one gets....
First trick is to establish whether the radio has another audio out for digital mode operation. It *may* be cleaner and less of a bother to
connect to. It also usually means this output is independent of the
volume control so you can vary that without affecting the input to the computer.
If not then the speaker output is an okay place to use. Rather than
simply connect through a inline resitor to get the level down to what
the computer line-in expects it might be worthwhile setting up a (say)
1K pot accross the spkr itself and setting that to the right level
(start at the zero output end). It is important in many digital modes to
keep the linearity as close to perfect as possible. This often means
setting the sound card line input in mid range and the rig output to a
point where the distortion (if any) bought about by the final audio amp
is kept to a minimum (hence the pot on the o/p).
Also be very wary of introducing earth loops into the system. For
initial tests it probably wont be an issue, but for the final setup
isolating the various audio grounds (with a transformer) and PTT line
(with an optocoupler) are worth doing. Mixing mains noise onto the
digital signal isnt real good for its reliability!
Also avoid using the mic input to the sound card. Its usually noisy.
Cheers Bob W5/VK2YQA
Frank wrote:
I'm new to the digital modes, and am about to buy an interface to try them out. Can anyone comment on the best way to tap my rig's (IC-756 P2) audio out? Should I simply connect a line in parallel with my external speaker and run that to the audio-in on the interface? Suggestions welcomed!
73,
Frank
W�MHZ
--- Synchronet 3.21b-Linux NewsLink 1.2