[TenTec] Omni VI frequency jumping/drifting

[w0ep]

I don't disbelieve what you are saying... but I wonder if you've

got a bad solder joint or other kind of physical crack somewhere,

some capacitor has more or less capacitance depending on the temp

expansion?






On 06/28/2018 08:40 AM, k4mt1950 at charter.net wrote:
> Stan:
> I have had the exact same problem with my Omni VI. There is a
> procedure to properly adjust band crystals. It is:
> Omni VI Lock PulseRig should be on for at least 1/2 hour.Check 10MHz
> REF at pin 9 of U12.Adjust 10MHz REF with C31.Check for lock pulse at
> pin 11 of U13, Scope probe on x10 position; .2 volts per div, and .1us
> time/div.Adjust L12 thru L21 on Xtal Osc. LO Mixer Bd. for the
> narrowest wave form.
> I did this but it did not help. I tuned in WWV and watched it on a
> waterfall and you could see carrier drifting back and forth. I was
> missing over half of the FT8 decodes as a result.
> What I found is PLL circuit on logic board is very temp sensitive. I
> tried to locate a part but the entire thing is that way. I found by
> putting a very small fin blowing across logic board completely
> eliminated the drift cycling.
> FT8 now works perfectly. Put the fan along the right side (looking
> from front) and not back panel. Back panel heats up during TX and when
> I put my fan there the problem got worse when I went into TX.
> Afraid its a design flaw and cant be fixed any other way.
> Gary K4MT
>
> 	-----------------------------------------From: "Stan Gammons"
> To: "Discussion of Ten-Tec Equipment"
> Cc:
> Sent: Wednesday June 27 2018 7:38:42PM
> Subject: [TenTec] Omni VI frequency jumping/drifting
>
>   Hi Everyone,
>
>   My Omni VI has decided to throw a few more fits. First the frequency
>   jumped on 30 meters, but FT8 signals still decode fine. So I let it
> go
>   and didn't mess with it. Lately 40 meters has started throwing fits
> and
>   it's much worse than 30 meters. Looking at the FT8 waterfall, at
> times
>   it will drift during the 15 seconds and it's bad enough the FT8
> signal
>   won't decode. I sent another email to the list with the waterfall pic
>
>   attached, but the message was too large and got rejected. I tried
>   tweaking the coils on the crystal oscillator board. It might have
>   helped 30 meters a little. Doesn't seem to have done much/anything
> for
>   40 meters though. Crystals gone bad maybe? If so, anyone know a
> source
>   now that ICM is no more?
>
>   73
>
>   Stan
>   KM4HQE
>
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