[TenTec] Broadcast Interference Fix for the Corsair II

[Joe]

You ask my question more clearly.

Joe, N4YG
----- Original Message ----- 
From: "Barry N1EU" <barry.n1eu at gmail.com>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Monday, September 19, 2011 6:40 AM
Subject: Re: [TenTec] Broadcast Interference Fix for the Corsair II


> 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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