Retransmission Operating Procedures (cont)

(4) Use the retransmission interference charts

receiver frequencies that are likely to interfere with each

(fig. FO-1) as a guide in selecting frequencies that will

other. To use the chart, find the axis for all transmitter

not interfere with the radio that is continually in close

frequencies selected to use and go up to each receiver

proximity to the other. These charts are used to

frequency in use; change any receiver frequencies that

determine interfering frequencies that should not be

intersect at a darkened interference line. An example of

selected for use by retransmission configuration ARC-

using the chart is given below.

131 radio sets. The black areas indicate mutually

Example: Two ground stations desire to com-

interfering frequencies. For example, there would be

municate with each other through retransmission station

interference between 31.45 MHz and the following: 53.70

on 35.85 MHz (station 1) and 49.75 MHz (station 2).

(10 kHz), 54.45 MHz (10 kHz), 55.45 MHz (10 kHz),

This will require that FM-1 and FM-2 transceivers in the

57.30 (10 kHz), 60.15 (10 kHz), 61.55 MHz ( kHz),

AN/ASC-15A(V)1 and (2) be tuned to those frequencies.

etc.

Since 10 MHz exists between frequencies it will only be

(5) Observe the recommended minimum

necessary to check for interference on the

frequency versus distance restrictions given below.

retransmission interference chart figure.

(7) Transmitter frequency at 35.85 MHz will not

Minimum antenna distance separation

interfere with a receiver at 49.75 MHz. However, as

(whip antenna)

shown by the chart, a transmitter frequency at 49.75

Minimum Frequency

Between

MHz will interfere with a receiver at 35.85 MHz and

separation

Between

ANIARC-131

therefore, the two retransmission frequencies are not

required

AN/ARC-i31

radios on LOW

acceptable.

10 MHz

56 feet

5 feet

f In the event of an emergency situation wherein the

(6) On the retransmission interference chart,

TSEC/KY-28 is likely to be captured by the enemy

transmitter frequencies are plotted in MHz along the

forces, set the ZEROIZE switch on the C-8157/ARC to

bottom of the chart from left to right; receiver frequencies

up and open the access door on the TSEC/KY-28. Both

in MHz are plotted along the left-hand side of the chart

of these actions will zeroize the TSEC/KY-28 and make

from bottom to top. The heavy dark lines running

further cipher communication impossible.

through the chart are intersects of transmitter and

3-18