[TenTec] OMN VI must have a very quiet LO

[Bob McGraw - K4TAX]

I tend to agree with Barry.  The ATTN improves dynamic range while lowering 
RF Gain improves S/N ratio.

I'm amazed at many local ops, not in a contest or strong signal area, which 
run with the ATTN on and then raise the RF Gain to make up the loss.

73
Bob, K4TAX




----- Original Message ----- 
From: "Barry N1EU" <barry.n1eu at gmail.com>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Tuesday, November 04, 2014 10:05 AM
Subject: Re: [TenTec] OMN VI must have a very quiet LO


>I use similar filtering plus an Inrad 600hz roofing filter.  Yes, I
> definiterly also use LP (600).  I'm not sure about ATTN - I tend to think
> that leaving it ON and lowering RF Gain will result in lower noise level.
> ATTN would help dynamic range, but my roofing filter is already helping
> there.
>
> 73, Barry N1EU
>
> On Tue, Nov 4, 2014 at 3:50 PM, John Rippey <w3uls73 at gmail.com> wrote:
>
>> Thanks for the responses.
>>
>> Re the "1980s" design, I have an older ARRL handbook c. 2000 that goes
>> into the design of the OMNI VI in quite a lot of detail, including the
>> unique LO design. I knew it was good, but I had no idea . . .
>>
>> Jim: Here's how I do it (a variation of Barry's) on CW: ATTN on. LP
>> and NR on. 500 Hz filter (N2) in first IF, 250 Hz filter in second IF.
>> (Going to 500/500 raises noise floor a tad.) Vary the volume as
>> needed. Of course, with very weak signals, you do hear a bit of noise,
>> but not much, and in that case you may want to turn off the ATT and
>> vary the RF gain per Barry. An amazing design.
>>
>> 73,
>>
>> John, W3ULS
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