[WriteLog] Using the Sound Card

[Tom McDermott]

I use the Heil Pro+ headset with the HC-4 element, Writelog, and SSB
messages with an FT1000MP. It works quite well, but it took some effort
to get there.

In general, computer soundcard levels are about 20-30 dB higher than
microphone levels in most of the common amateur rigs. To boost the
microphone levels to the point where it is digitized well (minimal
noise) by the soundcard, I use a 20 dB audio amplifier powered by a 9V
battery. It's a simple design and includes RC filters on the input and
output to keep the RF out (1.5KW amplifier less than 12 inches away = no
RFI). Battery power also helps to prevent RFI or grounding problems.
This amp is in-line from the Heil headset to the soundcard mic input.
Some soundcards have a programmable 20 dB gain boost on the mic input,
but my WinXP software sometimes randomly turns it off. Even when this
boost is on, it seems to introduce some noise. This setup works better
with it off and instead using the external audio amplifier.

Going from the soundcard to the phone-patch input, the problem is the
opposite, lowering the soundcard level by 20 dB going to the radio. I
use a small 1:1 transformer and a 20 dB attenuator (2 resistors). The
transformer breaks up a ground loop that is heard as a once-per-second
beep - it's caused by the RS-232 computer interface ground current when
Writelog polls the rig for frequency and status. The RS-232 ground
return currents share the audio ground path back to the computer unless
you break up the audio path with the transformer. The 20 dB pad is
ABSOLUTELY required; without it there is a lot of hum and other noise
from the computer, with it, it is virtually impossible to distinguish
"recorded audio" from "live audio" from "Heil directly to mic jack"
audio.

	-- Tom, N5EG



W4ATL writes:
> I am trying to use my computer's sound card for SSB message recording
with
> Writelog and I it is not working well.  When using my Heil headset
with
> the HC-4 element, the audio is extremely low.  I have all of the gains
> cranked to maximum on the WL sound mixer window.  An old Radio Shack
> microphone seems to work well and has more gain, but I would like to
use
> my Heil headset during contests.  The headset works fine when plugged
into
> my radio. Any else run into these problems?