A computer analysis of a conical monopole for use at naval high frequency direction finding receiving sites.

194 Pages·1.5 MB·en_US

by  Lemos, Panayiotis Petros.;Adler, Richard William.

DUDLEY KNOX LIBRARY
NAVAL POSTGRADUATE SCHOOI
MOMTPnpy CA 93943-5101

NAVAL POSTGRADUATE SCHOOL
Monterey, California
THESIS
A COMPUTER ANALYSIS OF A CONICAL MONOPOLE
FOR USE AT NAVAL HIGH FREQUENCY
DIRECTION FINDING RECEIVING SITES
PARTI
by
Panayiotis Petros Lemos
December, 1992
Thesis Advisor: Richard W. Adler
Approved for public release; distribution is unlimited.

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tV TITLE (Include Security Classification) A COMPUTER ANALYSIS OF A CONICAL MONOPOLE FOR USE AT
NAVAL HIGH FREQUENCY RECEIVING SITES PART
I
12. PERSONAL AUTHOR(S)
LEMOS, Panayiotis Petros
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Master's Thesis FROM TO 1992 December 75
16 supplementary NOTATioNThe views expressed in this thesis are those of the
author and do not reflect the official policy or position of the Depart-
ment of Defense or the US Government.
17 COSATI CODES 18 SUBJECT TERMS (Continue on reverse if necessary and identify by block number)
FIELD GROUP SUB-GROUP antenna; HF; conical monopole; direction finding
19 ABSTRACT (Continue on reverse if necessary and identify by block number)
The Naval Security Group (NSG) High Frequency Direction Finding (HFDF)
sites use large circularly disposed antenna arrays (CDAA) with moderate
to high gain beams. Omnidirectional coverage is presently obtained by
combining 8 to 120 elements of the CDAA. Recent measurements of site
performance reveal that most HFDF sites suffer from high noise levels.
Much of the noise is generated in the RF distribution system. This
noise contaminates the CDAA omni signals, greatly reducing their effec-
tiveness. One proposed solution to the problem is to use a semi-remotely
located broadband conical monopole (CM), which does not connect through
the noisy RF distribution system. A proof-of-performance comparing the
CM and CDAA omnis is commencing at NSG.
In this thesis, the performance of the model 2012AA Conical Monopole
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ADLER R.W. 408-646-2352 EC/Ab
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Antenna is studied in the presence of finite ground using the Numerical
Electromagnetics Code (NEC-3). Ground constants used in this study
were obtained for two locations where the CM are installed; Northwest,
VA, and Winter Harbor, ME. The performance of the combined antenna/
ground system was simulated over a frequency range from 2 to 30 MHz
(HF), for various ground constants with particular emphasis on the
,
elevation plane radiation patterns
The study concludes that the CM operates effectively in the fre-
quency range of interest with some exceptions. These occur at
frequencies where there is probable transitional range where the mode
of operation of the antenna is transferred from that of an inverted
cone to that of a broad monopole.
Finally, this study confirms that in order for an antenna/ground
model to provide a representative and effective simulation, the ground
constants in the vicinity of the antenna should be carefully measured
and averaged over an adequate number of samples.
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