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Spiral cone antenna
93491-2
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Wideband surveillance antenna · 1 - 10 GHz
93491-2 is a wideband UHF/SHF
conical log spiral antenna,
made by Stoddard Electro Systems in Gardena (California, USA).
The antenna covers 1 to 10 GHz and is intended for calibrations,
EMC measurements and surveillance purposes.
It is housed in a grey/blue polyester cone enclosure.
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The antenna is about 375 mm long and has a diameter of 130 mm
at its widest point (i.e. the rear). It has the shape of a cone,
with a sharp tip at the front, as shown in the image on the right.
Close to the rear end is a mounting hole that can be used to
put the antenna on a (wooden) tripod or suspend it from the ceiling.
At the rear is an N-type socket that should be connected to a suitable
receiver
or measuring device.
In many surveillance applications the
antenna is used complementary to the (larger)
63490-1 that covers the 200 MHz to 1 GHz frequency range.
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The design is based on the ETS-3102 — made by ETS-Lindgren in Austin
(Texas, USA) — but is more rugged, as the semi-rigid feedline that forms
an essential part of the construction, is fully
covered by the enclosure, whilst on the original ETS-3102 it runs over
the outside surface [D].
The spiral cone antenna was developed by John D. Dyson in 1958,
and is described in great detail
in US Patent 2,958,08,
complete with full mathematical backgrounds [2].
Additional information can be found on Wikipedia [1].
Antennas of this type can be used over a very wide frequency band
and their impedance is more or less constant over the entire range.
For this reason, they are extremely useful for monitoring the frequency
spectrum and for other surveillance applications.
Because it is circularly polarized, it can receive fields in any direction
(horizontal and vertical).
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Known spiral log antennnas
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Device Dual element conical spiral antenna Model 93491-2 Dimensions 375 x 130 mm Ø Weight 500 grams Frequency 1 - 10 GHz Impedance 50 Ω Connector N-type (female) Max. power 50 Watt Peak power 100 Watt VSWR 1.6 : 1 Pattern Directional Polarization Circular (right)
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- John D. Dyson, An unidirectional equiangular sprial antenna
Technical Report No. 33, 10 July 1958.
- John D. Dyson, A theoretical study of the equiangular sprial antenna
Technical Report No. 35, 12 September 1958.
- A Survey of the Very Wide Band and Frequency Independent Antennas —
1945 to the Present — John. D. Dyson, 16 August 1961.
Journal of Research of the National Burau of Standards (now: NIST).
Volume 66D, No. 1, January-February 1962.
- Model 3100 Series Conical Log Spiral Antennas, User Manual
ETS-Lindgren, September 2002. Revision C, March 2013.
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© Crypto Museum. Created: Thursday 22 March 2018. Last changed: Sunday, 16 October 2022 - 09:17 CET.
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