Topband: Using a 40673 in a KD9SV 160m pre-amp?

[Greg - ZL3IX]

> The reason for using the KD9SV premap with its tuned input and output is
> because other 1.8MHz preamps tried have been affected by the presence of
> strong local medium wave signals, causing cross modulation/intermodulation
> to occur.
>
My solution to this, Steve, is to insert a high pass filter between the
antenna and the preamp.  The one I use has at least 40 dB rejection from 1.6
MHz downwards.  Then not only is the preamp protected, but also the input
stage of the radio.  Even with high dynamic range preamps, such as the
2N5109 varieties (eg W7IUV), the intermod problem may still exist if the
radio cannot handle the BC signals.

With the HPF in, the 40673, even with its diodes, is unlikely to be affected
by the BC signals, unless they are much stronger in VK6 than in ZL3!  I have
a 6 kW MWBC station 5 km down the road, and I use a J310 preamp, which is
hardly in the high dynamic range class.

73, Greg, ZL3IX