Has anybody here built the Voice Blaster drawn by K8CC in the Voice
Blaster documentation package? I just did, and am having some problems
with it. First off, when using a LPT port, it appears to me that LPT
pin 2 is never asserted, which means that relay K1 never closes. Since
pin 3 does get asserted, relay K2 will close and so it is possible to
record a message which you can play back to a speaker. But since
K1 never closes, you don't pull down PTT so it's all just an interesting
experiment.
If, on the other hand, you use a COM port, then it appears almost the
reverse happens. When you are recording, both pin 4 and pin 20 are
asserted, so you pull down PTT, MIC input goes to the Sound Blaster's
MIC input, and every thing is peachy. But when you play back a recorded
message, only pin 4 is asserted; pin 20 is not. So relay K1 closes and
you do pull down PTT. But since K2 doesn't switch, you don't have a
full Mic circuit from Mic In to Mic Out. I do have the option selected
in the pop-up menu (option "X" toggled) that should allow this to
happen. What I can't understand is why I'm not feeding any signal to
the transceiver's Mic Input. Obviously I've got more bugs I haven't
found yet. At first I thought it might have to do with the audio
isolation transformer, but I don't see how I could record if that were
wired wrong. (Note it's a 1:1 transformer, yet the package shows a
different resistance on the primary than on the secondary. Indeed,
it measures that way! I wired the secondary to the Sound Blaster
speaker output and the primary to the Mic circuit on K1B/K2A. Is this
a problem?)
Another problem I've got is an excessive level of audio hum. I was
careful to keep microphone ground separate from all other grounds to
prevent this, but it's still a much higher level of hum on my recorded
messages than on the LTA-provided message. And, interestingly, that
LTA message has much more hum than other .WAV files I have lying
around.
Comments from anybody else who has been down this same road? This
software just came in the mail two weeks ago, so it should be pretty
current.
AA6KX/Bruce Sawyer
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