[TenTec] Broadcast Interference Fix for the Corsair II

[Barry N1EU]

>From the description of the mod in the posting, it seems like a
worthwhile mod.  I was wondering:

1.  Has anyone pulled the 80969 LPF-TR board and can describe what's
involved/how difficult a task it is?
2.  Why is the schematic marked "optional hi pass not installed" in
the section that contains the junction of C7, L9, and L10. (new
connection for Q2 collector)?  Is the hi pass filter actually present
despite that notation?

73, Barry N1EU

On Sun, Sep 18, 2011 at 10:14 PM, Joe <joe at n4yg.com> wrote:
>
> 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 at juno.com
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