RadioBanter - View Single Post

November 17th 05, 05:27 AM posted to rec.radio.amateur.antenna

wrote:
All,

Do any of you see a problem in RF tuning or resonance with supporting a
vertical pipe radiator by a vertical pipe base, seperated by a PVC
coupler so that the base can be part of the ground system?

No. I have a four-square array in which each element is a quarter
wavelength at 40 meters, 1-1/4" diameter at the bottom, and clamped to
an 8 foot galvanized steel chain link fence line pole driven 4 feet into
the ground. The antenna and 4 feet of protruding post are spaced 1/4" by
slices of thick wall PVC conduit, and clamped with muffler clamps. The
protruding pipe is connected to the ground system. They've been up for
about 20 years. The only effect of the pipe on 40 is to add a bit of
shunt C at the base of the antenna which lowers the self-resonant
frequency a bit. The effect is considerably more pronounced at higher
frequencies where the antenna base impedance is higher.

Roy Lewallen, W7EL