7235 Watson-Watt HF DF Antenna
The 7235 is a compact, active antenna system
used for direction finding of signals in the MF and
HF bands. It is packaged in a small, but rugged,
plastic housing that is suitable for fixed or
mobile installations.
The 7235 is optimized over the range of 500 kHz
to 20 MHz and operates over the frequency
range of 300 kHz to 30 MHz. It is designed for DF
systems using the Watson-Watt DF method.
In this system, the azimuth angle of arrival
of a vertically polarized signal is determined
by measuring and comparing the phases and
amplitudes of the received signal at the outputs
of two loop antennas which are oriented at 90
degrees to each other.
DF elusive HF and MF signals with
a small but powerful solution.
The 7235 consists of two identical receiving
loop antennas arranged in a “crossed loop”
configuration. Because loop antennas that
operate at low frequencies tend to be very large,
the 7235 uses an active magnetic loop design
to minimize the physical size of the antenna. The
7235 contains two multi-turn loop antennas
that are wound around high permeability ferrite
rods to increase the effective area of the loop,
and thereby increase the antenna sensitivity
at low frequencies. The signal output of each
loop is buffered by a high-dynamic-range active
amplifier to improve the antenna noise figure.
In addition to the two active loops, the 7235
system includes a low-profile active monopole
antenna (Model 7031). The signal from this
third antenna is used as a reference in the DF
algorithm to eliminate the 180 degree angle of
arrival ambiguity that is inherent in crossed loop
DF antennas.
K E Y F E AT U R E S
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Compact MF/HF DF antenna suitable
for mobile applications
Rugged and waterproof
0.3 to 30 MHz frequency range
10 degree RMS DF accuracy
Ferrite-wound, active crossed loop
design provides excellent sensitivity in
a small package
High-dynamic-range amplifiers
minimize IMD spurious
Ideal for use in TCI Series 700 SMS/
DF systems
7235 Summary Specifications
T C I I N T E R N AT I O N A L , I N C .
3541 Gateway Blvd.
Model 7235
Specifications
Fremont, CA 94538-6585 USA
TEL: 1-510-687-6100
USA: 1-800-824-8074
FAX: 1-510-687-6101
Configuration
Dual loop antennas (crossed) with matching networks and dual 30 dB low noise
amplifiers
Frequency Range
300 kHz - 30 MHz*
Sensitivity
0.2 microvolt/meter (typical for 0 dB SNR output in 1 Hz bandwidth, 2-30 MHz)
RF Outputs
Two BNC connectors from crossed loops, one Type N from 7031
Reference Antenna**
Power
+ 18 to +24 VDC,
Dual loop: 500 ma max.,
Single loop: 250 ma max.
Size
12” x 15” x 6.5” high (295 x 370 x 165 mm)
(two loops and two amplifiers in single enclosure)
Weight
18 lb (8 kg), dual loop
13 lb (6 kg), single loop
Optional Configuration
Single loop/amplifier per enclosure packaging (suitable for certain mobile
applications in which each half of crossed loops must be separated)
www.tcibr.com
* 7235 operating range is 300 kHz to 30 MHz and is optimized over the range of 500 kHz to 20 MHz.
** Refer to 7031 data sheet for companion reference antenna specifications.
Simplified Block Diagram of 7235 Dual Crossed Loop HFDF Antenna
M AT C H I N G
N ETWORK
30 dB RF Amps
M AT C H I N G
N ETWORK
Company proprietary
Data and specifications subject to change without notification.
Not for distribution without prior permission from TCI.
7235-11-11-15
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