[IRCA] Paran antennas

["Dan Strassberg" <dan.strassberg@xxxxxxx>]

Both of the Parans that I know anything about have stated horizontal-plane
efficiencies of 281.7 mV/m/kW@ 1 km. That efficiency is (probably NOT
accidentally) the minimum for Class B and D AMs. This odd coincidence
suggests that the consulting engineers didn't do detailed proofs of
performance but instead relied on published data for Parans--most likely the
data the FCC used to generically certify Parans for use at nondirectional
AMs. (When normalized for wavelength, the physical dimensions of the two
Parans I know of are not the same, though they are close.) Anyhow, it may be
naive to assume that vertical-radiation patterns achieved through top
loading (and any other mystical properties of the Paran design) are the same
as those of a standard series-fed vertical radiator having the same
horizontal-plane efficiency (that is, a tower approximately 54-degrees high
with a "standard" ground system of 120 90-degree radials). The only ways I
know of to determine the vertical patterns are a) simulation, b)
measurements on a small-scale physical model operating at a much higher
frequency, or c) measurements on the real thing made by taking an FIM up in
a helicopter (!)

But remember if that if the horizontal efficiencies are equal, it does not
seem logical that the vertical radiation patterns should differ much.
Assuming equal loop resistance, I believe that the integration of the
radiated energy over a hemishphere has to come out the same if the power is
the same. Although a standard 54-degree stick has no high-angle lobe in its
vertical pattern, its skywave performance is not wonderful. High-angle lobes
don't develop until the tower height exceeds 180 degrees. They become quite
troublesome above about 215 degrees, at which point the station becomes
subject to close-in "phasing" under sky-wave conditions because the skywave
intermittently cancels the groundwave even in areas of relatively high
groundwave field intensity. Nevertheless, the skywave performance of a
series-fed 54-degree stick is inferior to that of an otherwise similar 80-
or 90-degree stick. I find it hard to imagine how the Paran's vertical
pattern could improve a lot on the 54-degree situation and still maintain an
efficiency of just 281.7 mV/m/kW@ 1 km.

--
Dan Strassberg, dan.strassberg@xxxxxxx
eFax 707-215-6367




_______________________________________________
IRCA mailing list
IRCA@xxxxxxxxxxxxxxxx
http://arizona.hard-core-dx.com/mailman/listinfo/irca

Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers

For more information: http://www.ircaonline.org

To Post a message: irca@xxxxxxxxxxxxxxxx