[TenTec] Re; Adding 2.8 kHz filters to OMNI VI

[al_lorona at agilent.com]

> Without drastic surgery, you'll only see modest improvements 
> in the audio response, especially at the bass end of the 
> spectrum.  The Omni was never intended to do hi-fi ssb.
> 
> 73,
> Barry N1EU
> 

That's right. The bottom line is that in the Omni VI, the audio is always routed to the DSP, which acts as a high pass filter to roll off everything below about 300 Hz. You can't turn this function off. So, whatever you do to the audio below 300 Hz will never be heard.

I made some measurements once of the Inrad filters vs. the Ten Tec filters and there is definitely less passband ripple with the Inrads (George is right, those Inrads are wonderfully flat). The TT filters were actually flatter than everybody thinks they are, but there is a passband ripple of right around 2 dB. Is it audible? Probably there is some subjective improvement to listening to a signal with the Inrad filters, but in the big picture it isn't a night-and-day difference. It is an incremental step toward improving the Omni's SSB sound.

By putting the 2.8 kHz wide filter in the first IF slot, you have actually widened your transmit audio to 2.8 kHz as well. This transmitted audio will not be affected by the DSP that I mentioned earlier.

Yes, I strongly recommend that you check the carrier balance. Key the PTT on your Omni while you listen on another receiver. With the PTT held down, tune above and below your signal on the 2nd receiver until you hear your carrier. You won't miss it; it's a constant carrier tone. That's what you have to get rid of by adjusting the carrier null on your Omni.


Regards,

Al  W6LX