For casual ham use, 100W or more, and a good antenna, I would roll off
the low end of ANY mic a moderate amount, and I would set compression
for a few dB on peaks of speech. For the K3 and KX3, that means max cut
for the two lowest bands, and adjusting compression per the manual for a
corresponding indication on the meter..
For competitive use, and for any conditions that challenge
communications (like QRP, mobile, or greatly compromised antennas) I
would do more rolloff and increase the compression to about 10dB on
peaks. For the K3, the additional rolloff translates to max cut of the
200 Hz band and, by ear, optionally 3-6dB cut of the 400 Hz band.
That's a pretty generic recommendation for any mic and any voice. Mics
designed for communications have a peak around 3kHz, but pro mics
designed for music and broadcasting do not. For those mics, I would add
that peak, also doing it by ear.
The key to understanding all this is to realize that 1) any audio
content that does not contribute to speech intelligibility is wasted TX
power; 2) speech intelligibility is primarily provided by 800 Hz - 3 kHz
(and to a lesser extent, 400 Hz - 800 Hz); 3) any directional mic
emphasizes the lows due to proximity effect, putting even more power in
those useless low frequencies; 4) speech is quite dynamic, with 20dB or
more difference between loud and soft parts, so the AVERAGE TX power is
much less than the peak power ; 5) compression reduces the difference
between the loud and soft parts, increasing the average TX power,
preventing softer parts from fading into the noise.
73, Jim Brown K9YC
On 6/20/2012 6:10 AM, Robbins, James wrote:
> Good morning Jim,
> I'm wondering if you could expand a bit on your "competitive
> contesting and DX audio" settings? I'm not sure what audio
> emphasis/reduction you are making for this type of use.
> I am awaiting my KX3 and have purchased a CM500 for use with it. I am
> interested in recommended settings for various other non-contest
> purposes. I tend to do more "rag chew" contacts. I currently use an
> Icom IC-7410 with a Heil Pro which receives many good audio reports.
> I learn a lot from reading your input on the Elecraft reflector. It's
> thoughtful and obviously based in professional experience (which can't
> be said for many of the comments):. Many thanks.
> Jim Robbins
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