[TenTec] Omni C Sidetone

[WA3FIY]

I don't think the Omni C uses any IC's in the sidetone.  At 
least mine did not.  It used a unijunction transistor oscillator 
very similar to that used in the Triton, Corsair, Argosy and 
possibly others.  The output waveform is in the form of a 
sawtooth, very rich in harmonics.  That is then passed through 
a two pole (if I recall correctly) R/C filter removing the higher 
order harmonics but leaving some of the lower order ones.    I 
never found the tone too obnoxious but I usually did increase 
the value of the second filter capacitor by a factor of 5 or so.   
That reduces the amplitude of the sidetone but also reduces 
the harmonic content.

This modified sidetone and my Trimm Professional headphones 
produces the most pleasant sidetone of all my rigs.     

73,

-Lee-

On 4 Jul 2005 at 22:25, Richard Detweiler wrote:

> Hi,
> 
> I've played with several of these, the side tone oscilator probably needs 
> some new components around it.  It sounds nice when new, but after 30 years, 
> the caps can change a little. then it can sound rough.   All the components 
> on the side tone circuit are cheap, even the IC is cheap, probably less than 
> 4 bucks for all of it.
> 


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