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[email protected] · November 30th 15, 06:36 PM posted to uk.radio.amateur,rec.radio.amateur.antenna

In rec.radio.amateur.antenna Wayne wrote:

wrote in message ...

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.

Interesting. Doesn't seem like it would be worth the effort to add radials
in this case.

More radials in the fan, no, but more radials around the antenna, yes.

--
Jim Pennino

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