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

To: <tentec@contesting.com>
Subject: RE: [TenTec] Re; Adding 2.8 kHz filters to OMNI VI
From: <al_lorona@agilent.com>
Reply-to: tentec@contesting.com
Date: Thu, 6 Jan 2005 18:06:49 -0700
List-post: <mailto:tentec@contesting.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





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