CHAPTER 6. FILTER, RADIO INTERFERENCE F-1 139/GRC-1 59(V)

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

4 11/16

1 7/8

6 3/8

(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