[AMRadio] AM Speech processing

John Lawson jpl15 at panix.com
Mon Jan 23 15:06:23 EST 2006

   In regard to the several very interesting threads regarding AM Hi-Fi, 
intelligibility, and audio bandwidth / spectrum efficiency - I have some 
personal observations, and devices I use in my shack...

   It is sometimes quite instructive if a recording of your QSO can be made 
- especially if adjustments are carried out during the course of the QSO. 
Several folks on the bands are set up to record and playback over-the-air 
- and there a few who can render these recordings into a computer file 
which can be forwarded to you, or which you can can hear on a website. 
This will go a long way toward helping 'tweak' the audio side of things.

   There are multitudes of cheap audio processing devices available - on 
eBay and elsewhere.  Of course a "good" mike is number one, and in that 
regard you generally get whatcha pay for.  Then, it's hard to beat the 
combo of a small audio equalizer feeding a compressor/limiter of some 

   The EQ allows you to tailor your audio bandwidth for the task at hand - 
'broad' for HiFi work, 'narrow' for DX, or to eliminate some of the 
(wasted) energy in the bottom octaves when intelligibility is the issue.

   The compressor of course allows a maximum of audio energy to be applied 
to the transmitter for a given modulation percentage - in my case with the 
Valiant it's a very dramatic increase in signal level and 'punch'.

   Generally you can get these two devices for around $100 total - then 
it's possible that your microphone will need a pre-amp (if it's not 
already "powered"). I'd certainly consider the Compressor first, though. 
It's an easy 'fix' that might wake up some signals out there - good audio 

   Just my 200 millidollar...


John  KB6SCO

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