I have recently erected a 320m Bev at my new remote receive site. This
is the first Bev I have used in ZL ( I did have one in ZS), and it is
working extremely well. Since I also have an N2PK VNA (vector network
analyser) I decided to do an impedance sweep of the Bev at the feed point.
Before deciding on a value for the termination resistance, I measured
the DC resistance to ground at the far end, and chose a value of
resistor that would make the series combination up to 500 ohm. The
swept impedance is a bit irregular, but the peak to peak resistive
component varies between 465 and 505 ohm, so I don't think the
termination is far out. What surprised me at first, was the fact that
the reactive component is always capacitive (averaging about 1000 pF).
I had expected it to swing between slightly inductive and slightly
capacitive.
After further thought, I guess that the series capacitive reactance is
due to imperfect grounding at the feed end. I can imagine that my
ground stakes don't make DC contact with as much soil as they do AC
contact. Do the guru's agree with this supposition?
If anyone is interested, I can e-mail the R+jX plot.
73, Greg, ZL3IX
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