A (controlled) Blast from the Past

Something I saw reminded of the name: Vomax.  We used a speech processor called the Vomax on Field Day (1970s/80s).  It was a small box which connected between the mic and the rig - an audio speech processor.  Either it didn't sell too well or they are closely held by owners because I didn't see any on ebay.  Found this pic on eham.net:

source:  https://www.eham.net/data/classifieds/images/486395.jpg

As I recall it was very easy to use.  While talking into the mic the pot was turned until the green LED turned on and that was it, start transmitting.  It was supposed to make the signal 10 dB stronger without too much distortion.  I never heard one on the air but it seemed to work OK for us on Field Day.  There were several iterations of the Vomax, another looks similar to the picture above but the panel layout is reversed with the switch on the left.

The Vomax used 4 sets of active filters/clippers to split the audio into 4 bands and process each one separately and then re-filter and recombine them.  While the manual is on the web I didn't see a schematic.  This was the age of grinding the part numbers off of chips to keep the circuit a trade secret.

https://www.opweb.de/english/company/Maximillian_Associates/downloads/Maximillian_Associates--Vomax_SBP-4--user--ID8857.pdf

But I did find an article on page 12 of Ham Radio Magazine for September 1979 by NW7S, Wes.

https://archive.org/download/hamradiomag/ham_radio_magazine/Ham%20Radio%20Magazine%201979/09%20September%201979.pdf

I suspect that this design is pretty similar to the Vomax.  This is something that could be replicated fairly simply using DSP but it's still very build-able today over 40 years later with the exception of that Plessey chip used in the AGC.   Maybe add a circuit to add a circuit to perform the Kahn Symmetra-Peak  on the audio ?

Another project for the queue !

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm