> biases weren't enough or the UHF signals were strong enough. Using true
> HF PIN diodes instead of switching or 1N4007 should also help prevent
> that mixing. And the external TVI filter has been proven effective in a
> couple such cases.
I agree with Gerald. Something is occurring between the antenna port and
the BPF matrix. As I indicated in my last message, when I placed the Nye
Viking LPF on the output of the Omni Six, the problem was completely
solved -- but that was before I changed the T/R diodes to the high-voltage
But what I did not do in the 13 years thereafter was to check for the
problem after the PIN diodes were installed. The Viking filter was so
unobtrusive that it just stayed there, out of sight, out of mind, for the
duration. Since the filter has negligible loss below 30 MHz, I felt that
having extra LPF filtering was a good thing anyway.
I would just leave the filter connected to the rig and forget about it.
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