OK, Bob. I wasn't sure. I had ordered one of the 4 Khz filters and
was, obviously, interested.
73, Joe
Bob Henderson wrote:
Hi Joe
No...the Sherwood data is for the stock FT1kMPs. So far as I'm aware there
isn't yet any independent data at 2 kHz for the MPs with the Inrad roofing
filter.
Bob, 5B4AGN
----- Original Message -----
From: "Joe Giacobello" <k2xx@swva.net>
To: <tentec@contesting.com>
Sent: Friday, September 03, 2004 9:59 PM
Subject: Re: [TenTec] Re: [Ten-Tec] Alas, not for me
Bob, are Sherwood's data for the FT1KMPs with the 4 KHz Inrad roofing
filter installed?
73, Joe
Bob Henderson wrote:
----- Original Message -----
From: "John Rippey" <w3uls@3n.net>
Finally, with the new roofing filters forthcoming from INRAD, a bunch of
older radios soon are going to have sterling dynamic range capabilities,
and you won't have to jump through hoops like the mods required on the
TS-870, or shell out big bucks.
snip
I wonder if George's new filters will have the effect of discouraging
introduction of new ham rigs since the older ones are being given such
powerful new legs?
snip
This will be an interesting one when the full story is told. Certainly
so
far as the FT1kMP is concerned. The roofing filter from Inrad has a 4
kHz
b/w which makes quite a good choice for SSB but is a lot of b/w for CW.
Interestingly, the filter requires some additional amplification to get
over
its insertion loss and I understand that Inrad have opted to include
enough
amplification to get over that loss and add a little bit more. What
price
that extra amplification?
Figures published by Rob Sherwood
http://www.sherweng.com/Dayton_2004/Dynamic_Range_Data.pdf
show the following dynamic range numbers at 2 kHz:-
TT-Orion 1 kHz roofing 92db
FT1k MkV 70db
FT1k 69db
FT1kMkV Field 60db
Sherwood also states that an additional 6-7db improvement in IMD at 2 kHz
is
obtained with the Inrad 762 filter. This puts Orions range at 2 kHz up
to
98db or better. That's a full 28db better than the FT1k MkV and 38db
better
than the Field.
That's a big gap and one that can only widen when the roofing filter mod
is
added. The question is by how much? As a CW man, I wonder whether the
benefit in improved IMD at 5 kHz will outweigh the deterioration in IMD
at 2
kHz. I have an MP but for now my roofing filter dollars will stay in my
pocket. Time will tell.
Bob, 5B4AGN
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