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Page Title: CHAPTER 6. FILTER, RADIO INTERFERENCE F-1 139/GRC-1 59(V)
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TM 11-5820-554-12
CHAPTER 6
FILTER, RADIO INTERFERENCE F-1 139/GRC-1 59(V)
blanker is 40.0 MHz with a
6-1. Introduction
minimum bandwidth of 1 MHz
Filter, Radio Interference, F-1139/GRC-159(V)(noise
and a maximum bandwidth of 2
blanker) (Collins 136B-2), hereafter referred to as the
MHz
noise blanker, converts noise to bias pulses for gating
Sensitivity............................ A pulse signal input to the noise
blanker of 100 microvolts will cause
the receive circuits of the Collins KWM-2/2A. This
a minimum of 35 db reduction of
action minimizes receiver output noise that results from
gain in the receiver signal path
radiated noise present on both the noise blanker and
Spurious response ................ Internal noise and signals introduced
receiver antennas.  Noise present in the 40.0-MHz
............................................ by the noise blanker are less than
portion of the spectrum occurs simultaneously with that
............................................ 1.0- equivalent signal.
Input impedance .................. Noise-blanker amplifier: 50 ohms
in the high frequency (3 to 30 MHz) portion. The noise
............................................ nominal 50 percent unbalanced.
blanker should be provided with its own separately
Output impedance.
Signal blanking circuit: high
tuned 40.0-MHz antenna. Although a 6-foot quarter
impedance.
wave, coaxial-fed whip is best in a mobile installation,
Controls............................... Installation of the noise blanker
in some instances a broadcast whip can be used with
............................................ requires the addition of an RF gain
............................................ control (furnished with the kit).
reduced performance.  This can be accomplished
Tube complement functions Three RF noise and pulse
without disabling the broadcast receiver if adequate
amplifiers, one IF input and output
isolation is provided (fig. 6-1)
amplifier
6-2. Tabulated Data
6-3. Installation
.
Power source
Companion receiver power supply.
Installation of the noise blanker is not authorized at the
Frequency range
The blanking gate of the noise
organizational category. It is installed at direct support
blanker passes IF signals in the
category(TM  11-5820-554-34-8).
range of 1.5 to 4.0 MHz in the
companion transceiver. The input
frequency range of the noise
6-4.
Items Comprising an Operable Filter, Radio Interference F-1 139/GRC-1 59(V) .
Dimensions(in)
NSN
Item
Qty
Height
Depth
Width
Weight
(lb.)
5820-00-960-8526
Filter, Radio Interference WF 81139/GRC-159(V) noise blanker
1
4 11/16
1 7/8
6 3/8
1
(Collins 136B-2).
6-5. Operation
Set the function switch to NB. After a sufficient warm-
up period, turn the noise blanker gain control clockwise
until the noise level indicated on the S-meter drops
sharply. This is the threshold point of most efficient
noise blanker operation. Additional noise blanker gain
is not desirable and will degrade performance. The
required noise blanker gain setting is not a set and
ELODOOIO
forget adjustment. Changing conditions, such as those
Figure 6-1. Suggested connections for using broadcast
encountered in driving from one area into another, will
whip for both broadcast receiver and noise blanker.
change
Change 1 6-1


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