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Re: AO40Rcv and soundboards?

Soundcards were not designed for communications applications but for playing
music and video game sounds.  The 16 bit A/D's are probably ok but the poor
audio amplifiers, mixers, and PCB layout in front of it vary all over the

A few ideas:
1. Make sure you can record and playback signals(like clean voice signals
from your radio) using your PC soundcard recorder/playback software without
any hum or distortion.

2. Make sure all sound effects like 3D, reverb, or any tone controls are not

3. If using a microphone input, make sure it is not being overdriven and
causing distortion.  If your mixer controls are close to either limit, you
may have some problems. You may need a little resistor divider/attenuator to
reduce the radio audio to the millivolt levels needed by a mic input.

4. 60/120Hz AC hum pickup can be a problem.  It may not show up on the
waterfall display since the display doesn't go that low but would screw up
the decoder.

5. Another problem with sound cards is that some do not have accurate sample
rates.  The software may tell them to sample at 11025 Hz but the card will
round it to 11000.  This doesn't bother the video gamer but screws up any
software that depends on the correct sample rate.

6. Some of the built in soundcards may have a lot of background noise from
the digital circuitry.  My laptop has all sorts of birdies and squeals in
the audio.

7. Make sure you use a stereo plug and not a mono plug.  The mono plug may
short the two channels together and cause some problems.  Just hook to one
of the stereo channels.

Many times the el-cheapo $10 soundcards work better than the expensive ones
since they don't have all the fancy special effects signal processing
capability that distort the signals.

Unfortunately, there's not a lot of good answers for dealing with
soundcards.  Ya take what you get.


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