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Re: [TenTec] Omni 6 +

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] Omni 6 +
From: Ken Brown <ken.d.brown@hawaiiantel.net>
Reply-to: ken.d.brown@hawaiiantel.net,Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sun, 23 Jul 2006 10:54:38 -1000
List-post: <mailto:tentec@contesting.com>
Hi Don,

If there is a significant difference in the audio, comparing LSB and 
USB, the most likely reason is that the BFO frequencies for LSB and USB 
are not adjusted properly. The Omni VI manual lists the correct 
frequencies as 9.000000 MHz for LSB and 9.003000 MHz for USB. There is 
an order in which the adjustments should be made, which is important, 
because there are several trimmer capacitors and two crystals in the 
BFO. Some of the capacitors are in the circuit all the time and some are 
switched in by diodes only for some modes. If you do it in the wrong 
order, you'll probably never get it right.

The 2.4 kHz wide 9 MHz IF filter in the Omni should cover the frequency 
range of 9.000300 to 9.002700 MHz. When in LSB with the BFO running at 
9.000000 MHz the low end roll off due to the filter is at 300 Hz. In USB 
with the BFO running at 9.003000 MHz the low end roll off is also 300 
Hz. Based on your description of the problem, I would say that your BFO 
is running a frequency higher than 9.003000 MHz on USB. If it were 
running at 9.003300 MHz, the low end roll off would be at 600 Hz instead 
of 300 Hz. You would have less low end audio response.

By the way if you look at those numbers you'll realize that in the 9MHz 
IF, when you are in LSB mode, the radio is generating and receiving USB 
at 9 MHz. And  in USB it operates on 9.003 MHz LSB. It gets flipped over 
when it is mixed with the LO.

If the BFO frequencies are correct, the other possible cause of the 
problem is some non-symetrical filter shape which might be caused by a 
poor solder joint or a bad crystal in the 2.4 kHz BW 9 MHz IF filter. 
This is much less likely than improperly adjusted BFO frequencies.


Don Wright wrote:
> Need to balance the transmit and receive audio on LSB and USB, right now my 
> LSB is great full sound on transmit and receive, but on USB both transmit and 
> receive are squeaky narrow, can someone tell me if there is a pot on the 
> radio to adjust this and where it is located. 73.
> Don Wright WV4X
> dwright@copper.net
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