Correlation Between Thumbwheel Switch Settings and Electrical Frequency Synthesizer RF Output Frequencies

TM 11-5820-695-35

synthesizer rf output frequency, and the overall block

(1) Thumbwheel switch setting (first three digits).

diagram description of the electrical frequency

synthesizer.

b. Correlation Between Thumbwheel

Switch

Settings and Electrical Frequency Synthesizer RF

Output Frequencies. The thumbwheel switches on the

front panel of electrical frequency synthesizer select and

indicate a specific operating frequency in the 4400.0

MHz to 5000.0 MHz range. Any frequency in this range

can be selected. The electrical frequency synthesizer rf

output frequencies from 284.375 MHz to 303.11875

MHz correspond to Radio Set AN/ GRC-144 operating

frequencies from 4400.0 MHz to 4699.9 MHz. This rf

output frequency range (284.375 MHz to 303.11876

MHz) is repeated for operating frequencies from 4700.0

MHz to 4999.9 MHz.

An electrical frequency

synthesizer rf output frequency of 303.125 MHz

corresponds to a thumbwheel switch setting of 5000.0

MHz. Thus, the thumbwheel switches provide for the

selection of 6001 different operating frequencies in 0.1

MHz steps. The 5000.0 MHz frequency down to and

including the 4400.0 MHz frequency is a range of 600.1

MHz. The four thumbwheel switches provide a direct

reading of five digits in MHz. The first thumbwheel

switch (on the left) sets the first two digits of the Radio

Set AN/GRC-144 operating frequency. The last three

digits of the operating frequency are set respectively by

the remaining three thumbwheel switches. The chart

below lists the electrical frequency synthesizer rf output

frequency (frequency A) resulting from the thumbwheel

switch settings for the first three digits of the Radio Set

AN/GRC-144 operating frequency. It also lists the

additive frequency increments resulting from setting the

thumbwheel switches for the remaining two digits (fourth

and fifth) of the operating frequency. The fourth digit

additive frequency is listed as frequency B. The fifth

digit additive frequency is listed as frequency C.

Therefore, when the last two (of five) digits are set at a

number other than zero, the frequency electrical

synthesizer rf output frequency (F.) is the sum of

frequency A and the two additive frequencies B and C

(F,= Frequency A + Frequency B + Frequency C). For

example, assume that the thumbwheel switches are set

to an operating frequency of 4765.9 MHz. From the

chart below, the corresponding electrical frequency

synthesizer rf output frequency (F.) is calculated as

follows:

Frequency A (first three

= 288.125000 MHz

digits showing 476)

Frequency B (fourth digit

= 0.312500 MHz

showing 6)

Frequency C (fifth digit

= 0.056250 MHz

showing .9)

= 288.493750 MHz

2-32