Topband: Anyone purchased the ARRL book on Short Antennas for160???

[Charlie Cunningham]

Thanks, Richard!

Yes, that's exactly the paper I was trying to remember  for Dale Long
HH2/N3BNA last evening. In my "senior moment" I couldn't remember it late in
the evening. Perhaps it was you that sent me that link recently! Thanks so
much, Richard!!  Have a good day !!

73,
Charlie, K4OTV

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Richard
Fry
Sent: Wednesday, January 22, 2014 8:19 AM
To: topband at contesting.com
Subject: Topband: Anyone purchased the ARRL book on Short Antennas for160???

C. Cunningham wrote:
>If you get up to 4 symmetrical elevated radials there's not much to be 
>gained by adding more. There's been a lot of work done in the broadcast 
>industry using elevated radials to replace deteriorated buried radial 
>fields that shows that pretty clearly. It was published in some IEEE 
>transactions some years ago.

Probably this refers to the paper of Clarence Beverage titled "NEW AM 
BROADCAST ANTENNA DESIGNS HAVING FIELD VALIDATED PERFORMANCE."  It is 
available as a PDF download from http://www.commtechrf.com/downloads.asp .

Below is a quote from that paper showing that the __measured__ groundwave 
field at 1 km radiated by a base-insulated, 1/4-wave vertical using four 
elevated radials was within 0.14 decibels of that from a perfect 1/4-wave 
vertical monopole driven against 120 x 1/4-wave buried radials.

The r-f loss resistance of 120 x 1/4-wave buried radials used in a monopole 
antenna system typically is less than 2 ohms in the MW and low-HF bands, 
regardless of the conductivity of the earth in which they are buried.  The 
use of four elevated 1/4-wave radials in this system produced almost 
identical performance to using a full set of 120 x 1/4-wave buried radials.

"The first permanent use of an elevated radial ground system appears to be 
at WPCI, 1490 kHz in Greenville, South Carolina. This installation, designed

by William A. Culpepper, involved replacing a standard buried system with a 
four wire elevated system consisting of #10 solid copper wire, one quarter 
wave in length, and supported on treated wooden posts which keep the radials

4.9 meters above ground. The antenna radiation efficiency, based on field 
strength readings on the eight cardinal radials, was 302 mV/m at 1 kilometer

versus the predicted FCC value of 307 mV/m. The WPCI installation was unique

in that the tower was base insulated but the radials came right up to the 
tower, 4.9 meters above ground and terminated in insulators. The tower was 
fed from the tuning unit, through a piece of coax to the 5 meter point on 
the tower where the center conductor of the coax was attached to the tower 
and the shield to the elevated radials. This feed system resulted in a 
higher feed resistance than would normally be expected. Data on this 
facility was taken from the FCC files."

Guy Olinger wrote:
>Be careful not to extrapolate very specifically qualified broadcast 
>experience into ham radio. Originally FCC spec radials still make the close

>foreground earth appear VERY conductive, which is NOT an advantage one will

>have putting up two or four radials over plain old dirt, unless one is 
>talking about midwest USA 30 millisiemen super dirt.

A monopole system using ~ four evenly spaced, horizontal, elevated radials 
or an "FCP" does not need (or use) a highly-conductive region ("FCC spec 
radials") around the base of the vertical radiator, because in such antenna 
systems the r-f currents flowing on its vertical and horizontal wires to 
produce radiation do not travel through the earth.

Note that the system described in the quote from Clarence Beverage's paper 
(above) was installed/tested near Greenville, South Carolina -- a region 
having earth conductivity of not more than 4 mS/m per the FCC M3 
conductivity map, and probably less than that.  Yet it produced almost 100% 
radiation efficiency as measured by a broadcast consulting engineer using a 
calibrated field intensity meter.

Such characteristics would apply to the use of elevated radial systems by 
ham radio operators as well as they do for AM broadcast stations.

R. Fry
Broadcast Systems Engr (retired) 

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