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Omni VI

To: <tentec@contesting.com>
Subject: Omni VI
From: n4lq@iglou.com (Steve Ellington)
Date: Mon, 15 Jul 96 14:54 EDT
I've always wondered about the shielding on the TenTec rigs. Take the Omni-6
example. The top and bottom covers are painted and no obvious provisions
have been made for properly grounding the covers to the chassis. Furthermore,
the 8 phillps head screws that hold the covers on are insulated from them
with nylon washers, probably to prevent paint chips.

What ever happened to the old TVI prevention measures that included copper
plating, conductive fingers and multitudes of screws? From my Omni 6, I was
able to easly receive the 9mhz oscillators across the room even with the
covers on.
I can only immagine how easily 42 MHZ would radiate through the covers. 

If this is a big problem, perhaps you can take your own measures to prevent it.
First try to determine where the leak is then try bypassing or shielding
measures. I'de start by removing the nylon washers and scraping the paint off
the covers so the screws can make contact 73

>> On 20m, my Omni VI seems to put out an excessive amount of
>> third harmonics (in the 42 MHz region).  Is there something
>> I can do about this?
>> 2nd harmonics from 15m, and 6th harmonics from 40m, which
>> falls also in this 42 MHz region seems low.
>Hello Kok. What are the levels you measured on the various harmonics,
>and what method did you use.
>In linear service, there is an inherant attenuation of harmonic energy.
>In addition, TenTec uses good, solid bandpass filtering out of the
>amplifiers. I would suspect you may be running into the non-linear
>portion of the PA, causing some IMD products. If that is the case, a
>check with the engineers at TenTec is in order.
>Keep us informed, please!  de KL7HF
Steve Ellington N4LQ@iglou.com

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