[Elecraft] Overmodulation

Sat Oct 19 19:55:01 2002

Over-modulation is any time you exceed the proper r-f to audio ratio.
That will produce distortion because the r-f waveform can't accurately
duplicate the audio waveform. 

That's not possible with the K2. Automatic gain control keeps the right
audio-to-rf ratio under all conditions at any power up to 10 (or 100)
watts. 

The operator didn't help much with such an oddball report.

However, you might consider whether you were using compression. Some ops
consider the "sound" of audio compression as being "over modulating".
Your voice gets louder and less "natural" as you use SSBC levels above
1-1.

Another possible cause is an amplified mic. That is, and external
amplifier between your mic and the K2. If it is pumping too much audio
into the K2 mic input, it can cause distortion. If you are using an
amplified microphone, try turning down the mic amplifier. As long as ONE
bar of ALC flickers on occasional voice peaks, you are putting out the
full power from your K2. That's all the audio you need going into the
mic input. More may not necessarily cause any distortion - the K2's
automatic level control can handle quite a range - but it won't increase
your r-f output.  And too much can cause trouble. 

Are your running your power over 10 (or 100) watts? The K2 is NOT
designed for greater power and still meet the harmonic distortion
specifications in SSB. If you are 10 (or 100) watts, you are producing
more distortion than you should.

Finally, what does your signal sound like on another receiver? I am a
firm believer in doing real-world checks of my signal. If you don't have
another receiver that will tune the ham bands, perhaps you can hook up
with someone who can record your audio and send you a copy. The Sound
Recorder in Windows (if you've a computer in the shack running Windows)
is a handy way to capture the audio of the receiver for playback and
critical listening. 

Ron AC7AC
K2 # 1289

-----Original Message-----

I just got an overmodulation comment while QSOing on SSB at 10m.  Can
anyone 
tell me on what I need to look at?  This might be a stupid question but
I'm 
not entirely sure what it means to be overmodulated.  I'm not sure if I
know 
one if I hear one.  Any help is appreciated.  Thanks.

Regards,

Sam N2MXY
Elecraft K2 S# 1866

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