Richard--
Is it conventional to compare the surface wave fields at a distance so near
the Radial length and the wave length? 0.1 km Sounds like a lot, but it is
only 100m, which is low, in Lambda terms..
Bill--W4BSG
-----Original Message-----
From: Richard Fry
Sent: Sunday, March 01, 2015 12:08 PM
To: topband@contesting.com
Subject: Re: Topband: Modeling "Ground" and losses
The feedpoint connection, in all cases of vertical antennas, whether the
system is shunt fed or series fed, or even if it is an end-fed half wave,
ties one feed terminal to the ground or counterpoise system. It has to be
that way, and the current out into that counterpoise (whatever the
counterpoise is) has to be equal to the common mode current at the junction
flowing up into the radiator.
The link below leads to a NEC4 comparison of a 1/4WL vertical monopole using
four 1/4WL radial wires at 90-deg horizontal intervals. In one case the
radials are buried. In the other case they (and the monopole) are elevated
1 meter above the earth, and not connected to the earth by any metallic
path. Applied power in both cases is 100 watts, and earth conductivity in
both cases is 5 mS/m, d.c.5.
The surface wave fields at 0.1 km from these two configurations differ by
about 1.15 dB, which means that their radiated powers differ by about 30%.
If the total energy flowing into the monopole system with buried radials is
dictated only by its hard-wired connection through the transmission line
back to the transmitter, then what is accounting for the reduction of its
radiated power?
http://s20.postimg.org/453nz5vn1/160_M_QTR_WV_MONOPOLE_Flds.jpg
R. Fry
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