New Radios

[W8FN at aol.com]

G4BUO sez:

>but they could include bandpass
>filters for the ham bands which were bypassed on general coverage receive.

Hell, they don't even give you the jacks to put **your own** bandpass filters
in the circuit! First thing I did to my FT-1000 was put it face down on the
bench and drill two holes for RCA jacks to interrupt the coax line between
the T/R relay and the receiver front end so I could switch in my trusty
bandpass filters, as well as switch different receive antennas in and out.
Omission of such a simple thing is inexcusable on a contest-grade
radio!Looking at a friend's TS-850, I see it has the same problem. Guess
we're all supposed to go out and buy commercial filters like the ICE and
Dunestar. NOT!

Randy, W8FN
w8fn at aol.com

>From Randy Thompson <k5zd at iconics.com>  Tue Aug 29 03:20:43 1995
From: Randy Thompson <k5zd at iconics.com> (Randy Thompson)
Date: Mon, 28 Aug 1995 22:20:43 -0400 (EDT)
Subject: Antenna question
Message-ID: <Pine.LNX.3.91.950828221228.2249F-100000 at genesis.iconics.com>

Here is one for the technical wizards among us...

Yesterday I installed a Cushcraft 40-2CD for a local contester.  The 
tower is 90' of Rohn 25G with an LTA 7-el 10m beam at the top, and the 
new 40-2CD about 8' above that.

The antenna was built to have the SWR minimum around 7080.

We first applied RF when the antenna was 1' above the 10.  SWR minimum is
somewhere below the band (about 1.5:1 at 7000 and goes up in smooth curve
as you move up the band).  Raised the antenna up to final position hoping
it would get better -- it didn't change at all. 

So...looking for ideas on why this antenna is resonant below the band 
(>100 khz below where it should be).

Here is the interesting part.  The person who built the antenna used a 
Line Isolator instead of the suggested roll of coax choke.  He put the 
Isolator about 12-15" of coax back from the actual feed point.  Could it 
be that the coax between the isolator and the feed point is radiating -- 
making the antenna appear longer than it should be?


            +-----+      /

            +-----+      \
coax        isolator     feed
                   12"coax


Randy Thompson, K5ZD
k5zd at iconics.com