----- Original Message -----
From: "Tom Cathey" <k1jj@snet.net>
To: <Topband@contesting.com>
Sent: Thursday, March 14, 2002 9:47 AM
Subject: Topband: Tunable External Preselector for better Beverage S/N?
Hi Everyone,
A friend of mine suggested that I consider a tunable active (or passive)
preselector to improve S/N on my broadband, toroidal fed 1500' terminated
beverage.
I use an FT-1000D with diversity receive using the two receivers, two
antennas.
* His thinking was that the beverage and FT-1000D front end are both broad
band devices so they will let in additional noise from above and below the
desired 160M narrow band operating range.
Has anyone an opinion or experience with using a preselector for filtering
out this noise via a bandpass filter like this on 160M?
What kind of S/N improvement can be had, if any? If it's worthwhile, any
suggestions for a unit with some gain commercial or homebrew (to also make
up for the beverage loss) are appreciated!
Thanks!
73, Tom - K1JJ
CT
It should make no improvement. Overall reciever selectivity is determined in
the later stages of the reciever. In the early stages you want just enough
antenna noise to overcome the noise generated by each stage and no more.
More gain will not lead to a better noise figure, but to more suceptability
to intermodulation and overload.
John K9DX
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