I have an 160/80 coaxial loop at around 15 feet. It goes to a signal
limiter in the shack and on to a pre-amp and the RX only input of my
FT1000D. The loop is about 20 feet from my tower which I shunt feed for
160 and 80. The shunt feed is one position of an outboard manual B&W
375 antenna switch which also selects the HF antennas on the tower. The
switch is connected to the usual ANT RF SO239 of the D.
When listening through the RX ANT, if the coaxial RX loop plane is
aligned with the tower AND the shunt feet is selected for the normal RF
antenna input, the noise level drops about 2 S-units and signals seem
stronger compared to any other antenna selected from the B&W switch. As
I rotate the loop plane through to orthogonal to the tower, the effect
is reduced and disappears. That is, it then doesn't matter which
antenna the B&W switch is on. The noise level remains the same.
This happens on both 160 and 80. I'm not complaining. When the plane of
the loop is aligned with the tower, it's just about on Europe. (Some
nice openings to the West Coast would come in handy......)
I haven't seen anything in print about this specific scenario of
antenna coupling. Thought it might be of interest.
73, Steve WB6RSE
|