John,
Among my radios, I have an Omni 6 that I purchased in '92, which has been a
very solid performer in low band DX'ing and in all major contest.
I have a copy of the product detector that you mention and was going to
build it to try in my Omni 6. However a couple of my friends, who are
technically astute hams, tried that circuit and claimed they saw no
improvement. So I gave up that idea. I also have several Inrad filters in my
Omni 6, but honestly can't claim to you that they were really an operational
improvement from the stock Ten Tec filters. The measured 'blow-by' around
the Ten Tec filters is quite good in spite of the fact the filters have no
external shielding.
The Inrad bandpass filter that you refer to, I think, is specifically for
DX'ing or contesting in the lower 15kc of the 40m band. It, of course, does
not replace the 20kc wide roofing filter in the Omni. So yes, if you get a
strong signal inside your band pass filter, the Omni's 20kc wide filter is
going to pass that right on through. Rumors are that Inrad is testing a
replacement for that 20kc Omni roofing filter. That should be a major
improvement for the Omni. However adding filtering to an Omni 6, as you say,
is not going to make the Omni into an Orion.
My Omni 6 is one of the best, if not the best, radio's I've ever owned. With
the upcoming improvements in the Orion's firmware, it will certainly make my
Omni 6 the second best radio I've ever owned.
161
Tom - W4BQF
----- Original Message -----
From: "John CRUX" <G3JAG@patents.freeserve.co.uk>
To: <tentec@contesting.com>
Sent: Thursday, September 09, 2004 7:49 PM
Subject: TT [TenTec] "Upgrading" an Omni V or VI
>
> I still run my Omni-V.9 and I admit to having put a heap if INRAD filters
in
> there. Yes they work fine. But, and its a big BUT, after an awful lot of
use
> on the LF bands, there is little point in spending a raft of dollars on
> filters if you still have the relatively poor IMD performance of the
standard
> product detector. I still have that despite all the expensive, cascaded
> filters ahead of it.
>
> Some years back there was an article published on this. And there was a
fix
> for the Omni-VI in the shape of an add-on board with a much less
vulnerable
> IC detector using the high level mixer chip developed by Plessey, the
SL6440,
> (sadly now discontinued.)
> I managed to get the circuit and a couple of the chips, but shoehorning it
all
> into an Omni-V is not trivial and I chickened out ..
>
> In short, adding expensive filters to an old radio does not necessarily
cure
> everything. You do not end up with a Sherwooded R4C, or an Orion.
> You end up with an expensive Omni.
> I also have a 40m INRAD roofing filter I can switch in. It does cut out
the BC
> and other crud above 7015 and the commercial garbage below 7000. But it
does
> not fix in-band overload. .
>
> John G3JAG
> _______________________________________________
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