[TenTec] Omni C self-test

[Ken Brown]

>  More recent Tentecs mix the PTO to 27 MHz to take the difference
> for 18 MHz which puts the normal sideband on lower which doesn't match
> the rest of thee world, but it removes nearly all of the transmitter
> spur.
>   
And when using a crystal filter to reject the unwanted sideband, instead 
of using the phasing method of SSB generation, the unwanted sideband 
rejection is not degraded when using the "non-normal" sideband.