Derg:
Let me try to clear because you obviously are missing some of the key points "we" have discovered to date (aside from your somewhat odd-if-not-nonsensical waffle - and FYI, that in itself does not bother me, you are not on my ignore-list - I think your heart is probably about in the right place, just a few of your brain-cells seem a little deranged...):
- The issue is not additional RF emission from spark-plugs, magnetos, or other, since the radios and antenna are NOT directional - such noise would be present irrespective of the aircraft's orientation with respect to the source station.
- The above statement is further backed up by the fact that a hand-held radio does NOT pick-up the noise, nor do nav receivers.
- The fact that the new 'underside' antenna does not suffer the noise, infers the issue is related to the RF line-of-sight path when a station is on the nose, and the location of the VHF antenna and some other factor (bonding, ADF antenna, etc) in that straight-line path.
I have no idea of your background and really don't care, but methodical and thoughtful fault-finding doesn't seem to part of whatever "you" are.
Never mind - I'm sure you won't care a hoot what I have to say...
- GY