MANAGING HF CIRCUITS USING CHIRPSOUNDERS (Cont)

TM 11-5820-917-13

f. In setting up network operations, establish procedures for simultaneous

changing of sounder sweep limits of the RCS-4B and its associated TCS-4B's if

such becomes necessary. often, particularly during daytime or the occurrence of

strong Es, operation of 2-30 MHz sweeps will be desired. However, best nighttime

sweep limits will generally be 2-16 MHz.

g. Before setting up the network, all operators should agree on several frequen-

ties (say one in each MHz band from 2-7 MHz for path lengths under 2000 km) which

will serve as emergency fallback frequencies in the event of any comm loss of outage

in the network. All should agree on a pattern for monitoring these frequencies when

required (e.g. monitor the 2-MHz frequency for the first minute of a 5-minute period,

the 3-MHz frequency for the second minute, etc). These frequencies should be used

under the following conditions:

(1) For any communication within the network before the frequency manage-

ment system is operational; or

(2) To "bootstrap" the network. (After initial synchronization or an unex-

pected outage, the RCS-4B site operators transmit the frequency change instruc-

tions to start normal network operations on the best propagating emergency channel.)

h. Set up a procedure for regular network contact or "radio checks" even if no

traffic is being passed. This can often alert network operators of equipment problems

before the equipment fails to pass operational traffic.

i. In setting up operating frequencies for each circuit, the RCS-4B operator

should select a primary and an alternate. The alternate channel should be lower in

frequency than the primary. The alternate is used if (a) equipment problems pre-

clude tuning to the primary frequency, (b) sudden interference or jamming renders

the primary frequency unusable, or (c) a sudden outage catches the network by

surprise.

When a

circuit is operating via the Es mode, operators at both ends of the

circuit should

be aware of the situation, an the alternate frequency should be

selected from

the bank of frequencies propagating via F-mode. Avoid operation

within 30% of

the Es MOF.

k. In setting up a duplex circuit, the transmit frequency from the RCS-4B

site should always be lower than the receive frequency. In this way, frequency

change instructions can be transmitted even with outage in the higher frequency

channel.

l. To avoid unnecessary confusion, all operators should agree on a procedure

for frequency changing that accounts for possible tuning problems. For example,

allow a set maximum time limit to establish contact on a new frequency. If contact

is not made, agree to return to the old frequency to assess the situation. If con-

tact cannot be re-established on the old frequency after another set period of time,

agree to go to the alternate frequency. If that fails also, then a pattern for moni-

toring the emergency frequencies should be used.

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