Topband: Rig Comparisons

[Jim Brown]

On 8/2/2014 9:06 AM, Michael St. Angelo wrote:
> Jim,
>
> The Mobility industry has been using pre-distortion. It has finally been
> implemented in the Hermes and Apache Labs Transceivers by Warren C. Pratt.
> He has won the ARRL Technical Innovation award and justly deserves it:

Interesting technique. The late Richard C. Heyser, who worked at JPL in 
communications, predicted exactly this around 1980 to compensate for 
non-linearities in audio systems, which are much more varied and 
complex. At least a half dozen pro audio companies were doing things 
like this nearly 30 years ago with power amplifiers for studio monitors, 
and as far back as the '70s, several manufacturers sensed distortion in 
loudspeakers and used motional feedback to correct it. Good to see ham 
radio catching up.

Looking at the reference, the Hermes is the product of the TAPR ham 
research group, and a building block for SDRs. Apache is a new 
manufacturer of SDRs. The new Flex models are rumored to be much better 
than those reviewed by ARRL. But SDRs are a tiny fraction of the ham 
world -- the K3 and KX3 probably being the most widely used.

How many decades do you think it will take this concept to get to Yaesu, 
Kenwood, ICOM, and Ten Tec. How many years did it take Yaesu to fix 
their awful clicks? And none of them have learned about "the Pin One 
Problem," published in the Journal of the AES in 1995 (by ex-W3WJE, SK), 
which is a major cause of RF susceptibility (often called "RF in the 
shack").

73, Jim K9YC