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@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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