Posted by
John Magliacane on
Aug 28, 2005; 10:43pm
URL: http://elecraft.85.s1.nabble.com/EV664-tp381491p381501.html
Hi Ron.
> Are you suggesting that those low frequencies are somehow being distorted or
> causing other problems in the audio I.C. in the K2 before they get to the
> filter?
I would say: YES.
Ideally, the audio frequency response prior to the compressor should
closely match the IF bandwidth of the crystal filter. Here's why:
Excessive low-frequency response prior to the compressor forces the
compressor to react to audio energy that has no chance of ever making
it through the crystal filter. If the audio response is too wide, then
the compressor will react to the extraneous audio energy, essentially
"desensing" the balanced modulator and the stages that follow.
I would hazard a guess that this "desense" might even produce a
perception of low or "muffled" audio in some cases when sufficient
gain actually exists.
Since we are working with such a small audio bandwidth, the tighter
the control of the audio response prior to the compressor, the less
variation there will be between different microphones.
73, de John, KD2BD
Visit John on the Web at:
http://kd2bd.ham.org/.
.
.
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