[TenTec] Broadcast Interference Fix for the Corsair II

[Richard L. Ferranti]

I 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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