I initially used a top-loaded 75-ft tower for 160m. The R part of the
feedpoint Z was under 10-ohms. I reasoned that an antenna with more Z
might be more efficient. I installed a halyard at the 75-ft. point and
hauled up the midpoint of a half-wavelength (250-ft.) of #20 copper wire.
"Hertz" is the name for an end fed half-wave antenna. [The name comes
from Gustav Ludwig Hertz (1887-1975)]. The far end of the half-wave was
tethered by a dacron cord. This end of the wire was c. 30-ft. above
ground. The feedpoint end was tethered to a 6-ft. fiberglass electric
fence post. On the ground near the fence post was a 3' x 4' sheet of
20-gauge galvanized steel. A "dog-house" on the galvanized sheet held
the antenna's L-matching network. In order to match the antenna to
50-ohms, 55uH was needed. The variable C that I used was an 11kV, E.F.
Johnson Type-E , 200pF max. The feedpoint Z was a bit over 5k-ohms, so
the 3' x 4' galvanized sheet served as a gnd. By DC gear-motor driving
the var. C, 1.8 - 2.0 MHz could be covered from the radio room.
- Results:
Switching from the vertical to the Hertz did nothing for receive.
On transmit, the avg. difference was about 5db in favor of the Hertz.
cheers
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
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