[TenTec] Omni VI lock problem

[Bill Cotter]

Ken,

I had this problem on 30M where the receiver would 'whoop' once 
every 30sec or so. I sent the 6+ back to TT to have the problem 
corrected, along with the 10M birdies and an alignment. When it 
returned, they replaced the TCXO, and adjusted the PLL on 30M. And, 
the 10M band was much cleaner. Your problem may be a combination of 
these elements, considering all bands drop out of lock momentarily.

73 bill n4lg


At 06:55 PM 9/22/2007, you wrote:
>Hi all,
>
>My Omni VI has a cyclical drift problem. It sounds like a PLL 
>drifting
>away from lock and then being pulled back into lock over and over 
>again.
>My first guess was that one of the crystals or other components on 
>the
>XTAL OSC. - L.O. MIXER BOARD had aged to the point where it was
>difficult to keep it locked. I was hoping that a minor tweak to the
>appropriate slug tuned inductor would bring that oscillator back to a
>consistent lock. Then I discovered that it happens on all bands. 
>It is
>beyond reason to believe that all ten of the band select crystals and
>associated components have simultaneously aged to the point where 
>they
>all require an adjustment. So, I must conclude that something 
>common to
>all bands has changed.
>
>The problem does not change using different modes (CW, USB, LSB, 
>FSK) ,
>so I must conclude it is not a BFO problem (the BFO does not have any
>PLL circuitry anyway.
>
>The rate of the cyclical "drift and pull back into lock" rate does
>change depending on the band selected. The cyclical rate ranges 
>all the
>way from once every 12 seconds (on 40 meters), to nearly two times 
>per
>second (on 80, 20 and 15 meters. When I listen to the transmit 
>signal,
>it has the same cyclical drift. When I listen to the 20 MHz crystal
>oscillator it is solid and stable. When I disconnect the cable from
>connector 84 on the LOGIC BOARD, the "drift and pull back into lock"
>action stops, and of course the frequency shifts a bit and the 
>XTAL OSC
>is no longer locked to the 20 MHz master reference oscillator.
>
>It seems like I could make the problem go away by adjusting all the
>coils for each of the band select crystals, however I think there 
>must
>be a common fault that is really the cause of this problem.
>
>Anyone had a similar problem with an Omni VI? How did you fix it? 
>Where
>is the XTAL OSC. - L.O. MIXER BOARD located. It is not visible 
>from the
>top of the rig. Is it on the bottom side, or is it inside that box
>sandwiched between top and bottom?
>
>DE N6KB
>
>
>
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