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Old May 2nd 08, 09:45 PM posted to rec.radio.amateur.antenna
Dave Platt Dave Platt is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 464
Default 75 meter hamstick vs low dipole

In article ,
Buck wrote:

i fully understand that the HamStick is not a great antenna fro that
band, but how would the vertical ground plane made of a HamStick and
two full length radials compare to a dipole at the same 10 foot level?


I think it would compare badly to the dipole.

With the dipole, you'll have working in your favor the basic radiation
resistance of a dipole in free space, reduced by the proximity of the
dipole to the "reflector" (the lossy soil). Working against you,
will be the losses in the soil. It'll certainly be a cloudwarmer...
good for NVIS, not for DX as there will be little energy at a low
radiation angle.

If you short the dipole wires and use it as a two-wire sort-of-
elevated radial set, the radiation resistance of these wires will be
very close to zero - the far-field radiation from them will cancel out
almost entirely. You'll still have substantial losses in the soil, I
think, as the wires are only a small fraction of a wavelength above
the soil surface. The radiation resistance of the HamStick itself is
going to be quite low (an ohm or so??), and it certainly has a
substantial amount of loss resistance.

My SWAG is that by making this change, you might drop your radiation
efficiency from 25% (low dipole over lossy ground) to 5% or less
(lossy short vertical, over an inadequate radial network with
substantial ground losses). Don't trust these numbers!

what would the angle of radiation be like?


Probably much like that of any other very-short monopole over a lossy
ground... pretty much omnidirectional, with a modest null pointing
straight up.

It *may* have more low-angle radiation in the pattern than the
low-dipole arrangement, but I think you'd lose most or all of the
pattern advantage due to the lower radiation efficiency.

--
Dave Platt AE6EO
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