Re: [TenTec] Shields in Omni VI

[Ken Brown <ken.d.brown@hawaiiantel.net>]

Hi Steve,

That the pitch changes suggests that the loading of the different 
filters is changing the frequency of a spurious oscillation, somewhere. 
If it is a harmonic of the 15.3 MHz PBT oscillator, it would only have 
to be a small shift of 15.3 MHz to produce a few hundred Hz shift of say 
the 15 harmonic. Changing the 9 MHz filter being used should not change 
the loading on that oscillator though. Maybe one of the 9MHz IF amp 
stages is oscillating.
Ken N6KB

Steve Hunt wrote:
> Ken,
>
> Gary, W7TEA, kindly sent me a photo of the underside of his early Omni VI+ which has the 
> screening in place. There are no holes in my "inner panel" which would allow 
> screens to be attached, so this must have been a mod on later Omni VIs / Omni VI+s.
>
> I have put temporary screens in place but they made no difference!
>
> One final symptom on the "birdies" which totally mystifies me: If I adjust the 
> PBT control until I hear a birdie, then press the NAR button, the pitch of the birdie 
> changes by a few hundred Hz; pressing the NAR button again returns it to its original 
> pitch. I can't see anything on the schematics that would suggest that the NAR button 
> affects any of the oscillators!
>
> I think I'm just going to have to live with it.
>
> 73,
> Steve
>   ----- Original Message ----- 
>   From: Ken Brown 
>   To: Discussion of Ten-Tec Equipment 
>   Sent: Monday, November 27, 2006 2:01 AM
>   Subject: [TenTec] Shields in Omni VI
>
>
>   Hi Steve,
>
>   The photos in the manual for my Omni VI do not show any of the shielding 
>   in place. I was wondering if I was confused and that the cover plates I 
>   remembered are in my Paragon and not in the Omni VI. When I read the 
>   manual for the Omni VI in the section describing how to install the 
>   optional filters, it clearly states that you need to "Remove the panel 
>   covering the PBT board" or "Remove the panel covering the 9 MHz filter 
>   board." So, even without opening up my Omni VI, I think I can say with a 
>   fair degree of certainty, "Yes there should be cover plates over the 9 
>   MHz and 6.3 MHz optional  filter access holes." I will be interested to 
>   hear whether adding shielding plates over those holes makes the birdie 
>   go away.
>   Ken N6KB
>
>   Steve Hunt wrote:
>   Ken,
>    
>   I only just spotted your question about shield covers over the optional 
>   filter slots.
>    
>   There aren't any - just holes! Should there be? I don't recall seeing 
>   any obvious fixing holes for covers or I might have been suspicious.
>    
>   73,
>   Steve G3TXQ
>    
>    
>
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