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[email protected] · November 29th 15, 11:24 PM posted to uk.radio.amateur,rec.radio.amateur.antenna

In rec.radio.amateur.antenna wrote:
In rec.radio.amateur.antenna Wayne wrote:

wrote in message ...

In rec.radio.amateur.antenna gareth wrote:
Spike recently commented upon his success with DX by implementing at
the base of his vertical antenna a fan
of 300 ground wires pointing in the direction that he wished to work.

I've not seen my suggestion before, but why could one not just have
a 1/4 wave vertical, with the other 1/4 wave making up the dipole
being rotatable for the desired direction of working?

Out of curiousity, I modeled the following:

freq: 14.2 MHz

radial height: 3 inches

Material: #12 copper

ground: average

I optimized the radiator and radial lengths for minimum reactance and got:

radiator: 196 inches

radial: 190.6 inches

R: 75 Ohms

X: -0.4 Ohms

SWR: 1.5

Maximum gain: -1.8 dBi in the direction of the radial and an elevation
angle of 30 degrees

Reverse gain: -6.8 dBi

Polarization: primarily vertical with horizontal lobes 90 degrees to the
radial a -15 dB down from the max vertical gain.

Cool. Any idea what the numbers would be for the 300 radial configuration?

Likely not a lot of difference.

I could add a few, but not going to spend the time to add 300.

OK, I added radials for a total of 5 in a 45 degree spread and optimized
for minimum reactance.

radiator: 203 inches

radial: 186 inches

R: 52.4 Ohms

X: 0.4 Ohms

SWR: 1.1

Maximum gain: -.18 dBi in the direction of the radial and an elevation
angle of 30 degrees

Reverse gain: -3.7 dBi

Note with one radial the F/B ratio is about 5 dB and with five radials
it is about 3dB.

About the only thing I can see worth noting about this antenna is that
it shows more radials are better, but everyone already knows that.

--
Jim Pennino

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