Corsair II Broadcast Interference Fix

From the Ten-Tec Reflector August 24, 2000

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 rejecthigh-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