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RF and Microwave Components
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PROGRAMMABLE ATTENUATORS
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- Quartzlock dB line attenuators answer the need for high
performance, close tolerance, wide range attenuation.
Ease of use, reliability and repeatable results have
been achieved using latest techniques in cascaded pads.
THIS TIMESAVING RF LAB TOOL IS EQUALLY AT HOME IN
PRODUCTION TEST. Each attenuator stage is identical in
construction employing high reliability, high frequency
relays to direct the signal, which is routed either
direct or via an attenuator pad. Transmission line
techniques have been used throughout in order to
facilitate high frequency performance including surface
mounted components which exhibit far less parasitic
reactances than conventional resistors. Finish is
alachrome 1200.
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AE30-300
Antenna (H field loop)
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The principle of operation is that an rf voltage appears
across the terminals of a loop when it is placed in an
electromagnetic field. This voltage is proportional to
frequency for a given field strength. Therefore at Very
Low Frequencies, the voltage is very small, and requires
greater amplification. The new TL Loop uses a unique
feedback system to optimise the amplification factor.
The method uses a loop constructed of transmission line
in which the line is also part of the feedback system.
The antenna is broadband and requires no adjustment
other than orientation since it has deep broadside nulls
for "Vertically polarised ground waves. There is no null
in the vertical direction, as with whips, so that short
hop high angle sky wave reception and long hop low angle
reception can both be excellent. Best results are
obtained with a clear site. No radio frequency grounding
of the antenna is required.
A perfectly lossless antenna picks up more ambient
noise, due to atmospherics, interference, etc., as one
goes down in frequency. Such high levels of signal and
noise can be considerably attenuated without seriously
affecting the overall signal to noise ratio. In other
words a smaller less efficient antenna can be used just
as effectively coupled with a low noise amplifier.
Active antennas therefore do not produce high signal
levels but nor do they need to, S/N is what counts. It
is preferable that the antenna is positioned vertically,
just above ground in an open area. Being an antenna
which responds to the magnetic field component, it is
highly immune to capacitively coupled local interference
which is a common problem of active whips, and local
interference can be reduced either by nulling or by
relocating the antenna far away.
The antenna is highly portable yet may be permanently
installed outdoors. Permanent support is easily arranged
by attaching the loop to a circular hoop on a short
pole. The power requirements are 12V at 50mA. This is
fed via the coaxial cable from the receiver using an
'isolating T' section.
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Predictable Performance
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Computer optimised design
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Extremely broadband 10kHz
-30MHz
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Sensitivity set by received
background noise
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High linearity
complementary push pull amplifier
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Good response to high angle
and low angle DX
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Deep broadside nulls for
ground wave signals
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Easy to Use
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Mount near ground level
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Encapsulated for outdoor
use
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Very compact size: 1.3m
diameter
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Easily transported
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Noise Immunity
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Immunity to electrical
field interference
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Easily located away from
local interference sources
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Isolated from mains borne
interference
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Survives RF fields of 13V/m
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No Tuning
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No inconvenience
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No band changing elements
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Narrowband/ VLF version
30-300KHz
Applications
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