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Conical spiral antenna
23473-G2
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Wideband surveillance antenna · 1-12 GHz
23473-G2 is a wideband UHF/SHF spiral antenna, invented in 1959 by John
D. Dyson in the US, and currently manufactured by BAE Systems (US).
The antenna is commonly used for intercept and surveillance purposes,
for example as part of an airborne intercept station, or a mobile bug
sweeping system, like the Micro-Tel MSR-902C.
It is also known as NSN 5985-00-921-6898.
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The unit – shown on the right – is a dual element unidirectional
conical spiral antenna with right hand polarization,
that is fed at the tip of the cone (not at the base). It comprises
the S, L and X band and is suitable for frequencies between 1.0 and
12 GHz. The cone is approx. 13.5 cm long (5.25") and is 5 cm wide
at the base (2").
Although initially developed for mounting under an airplane,
the antenna has meanwhile become a popular item in the
technical surveillance and countermeasures (TSCM)
trade, in particular for finding UHF/SHF
covert listening devices (bugs).
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The antenna was developed by John D. Dyson in 1958, and is described
in US Patent 2,958,08
complete with full mathematical backgrounds [2].
It was introduced to the Army on 21 December 1965, where it received
National Stock Number 5985-00-921-6898.
According to the packaging,
the antenna shown here, was manufactured in the first quarter of 1968.
According to the public NSN database, the 23473-G2 is still being manufactured
today (2017) and is still an ITAR item 1 that has to be
demilitarized when it is no longer needed (i.e. destroyed),
to avoid its reuse [3].
Nevertheless, antennas like the 23473-G2 do appear for sale regularly
on public auction sites such as eBay, commonly for several hundred dollars.
In the past, the price for a single (new) 23473-G2 antenna was between
US$ 1,750 and US$ 2,720 [4]. It is currently (2017) available from BAE Systems
for no less than US$ 4,035 [5]. Theoretical backgrounds of the spiral antenna
can be found in a series of publications
by John D. Dyson in the late 1950s and early 1960s.
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ITAR = International Traffic In Arms Regulations.
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Known spiral log antennnas
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Device Dual element conical spiral antenna Frequency 1 - 12 GHz Band S, L, X Connector TNC Impedance 50 Ω Feedpoint Top Polarization Circular Right Part # 23473-G2 Stock # 2RM-5985-921-6898-E313 NSN 5985-00-921-6898 Date 1968 Q1 Length 6.000 inches Diameter 1.969 inches Mounting 4 holes of 0.125 inches, threaded
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© Crypto Museum. Created: Friday 20 October 2017. Last changed: Sunday, 16 October 2022 - 09:14 CET.
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