I had strong broadcast interference years ago. There were both harmonics and
intermodulation from several local AM stations.
After a lot of head scratching, we found that my tower's guy wires were not
making good contact with the tower. The guy wires were terminated at the
tower end with strain-relief devices which hooked over the tower legs. The
oxidation between those joints (six in all) were causing the mixing.
Cleaning up the tower legs and then electrically binding the guy wires to
the tower with copper braid completely eliminated the trouble.
For what it may be worth.
73 and good luck, Mike - N4NT -
----- Original Message -----
From: "Joe" <joe@n4yg.com>
To: "TenTec Discussion" <tentec@contesting.com>
Sent: Sunday, September 18, 2011 10:14 PM
Subject: [TenTec] Broadcast Interference Fix for the Corsair II
>
> Below is a posting I was so pleased to find in my search to find a
> solution for Broacast Radio Interference and hash on all bands of my
> Corsair II. I am anxious to try this fix but I the task of getting to the
> transistor Q2 seems to be almost impossible. I want to talk to Rick,
> WA6NCX, but I have not been able to get up with him. Failing that, I would
> like to talk to someone who has completed this fix. I fear that if I am
> not careful here I will do something that I will regret. I would
> appreciate any help.
>
> Joe, N4YG
>
> WA6NCX posting 24 Aug 2000Subject: [TenTec] Broadcast Interference Fix for
> the Corsair III heard tremendous hash on 160 - 40 meters whenever I
> hooked my Corsair II to
> a big 80-meter full-wave horizontal loop. The problem was traced to
> overload of
> switch transistor Q2 on the 80969 LPF-TR board. The transistor junctions
> were
> rectifying a strong local BC station (putting over a volt of rf into the
> receiver!), whose
> signals passed right through from the antenna to the SWR detector and xmtr
> LPF's,
> through the TR switch diodes and then into the Q2 collector without any
> help from
> the rig's BC-reject high-pass filter network (the transistor is connected
> *before*
> the high-pass filter).
>
> After fooling around with a few false starts (which TT helped with, but
> didn't solve),
> it dawned on me that the fix is to connect the Q2 collector *after* the BC
> band high
> pass filter network, so that the strong BC station signal is greatly
> attenuated before it
> gets to the Q2 collector. So all I did was cut the trace to the Q2
> collector and run a
> short wire from the Q2 collector to the output of the BCB reject high-pass
> filter,
> right at the "RX" connector on the 80969 circuit board (at the junction of
> C7, L9,
> and L10). This fixed the problem completely -- no more hash and nice
> quiet reception
> on 160 through 40 meters.
>
> -- Rick WA6NCX
> remler@juno.com
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