h. Rotate MHz and kHz tuning controls
to left until a stop is encountered
on MHz tuning control, and last
three digits displayed by VHF
COMM frequency indicator are
000. Note that 116.000 is displayed
by VHF COMM frequency indi-
i Rotate MHz tuning control to right;
note that second two digits from
left on VHF COMM frequency
indicator increase by 1 at each
detent position and the highest num-
ber obtained is 149.000.
j. Rotate kHz tuning control to right;
note that last three digits displayed
on VHF COMM frequency indica-
tor increase 25 kHz at each detent
k. Verify that COMM TEST switch is
firmly secured to front panel.
Check interconnecting cabling for evi-
Cables and connectors ----------
dence of fraying or excessive strain.
a. Check to see that mounting is secure-
ly fastened to aircraft frame.
b. Check to see that ground strap is
securely fastened to aircraft frame.
c. Check to see that resilient (shock)
mounts operate smoothly.
Set aircraft primary power switch to
Primary power ________________
a. Refer to appropriate air-
on and close circuit breakers that
supply 27.5 volts dc to radio set
and C1611D/U. Control unit panel
lamps should light.
Radio set power -------------- b.
Set control unit OFF-PWR to PWR.
VHF COMM frequency indicator
a. Tuning radio set to predetermined
frequency of local am. station.
Tuning action by radio set should
be completed in less than 4 seconds.
b. Set controls on aircraft C-1611D/AIC
b. Applicable aircraft manual
as required to operate radio set.
Press an aircraft push-to-talk switch;
tranceiver blower should operate.
Two-way communication opera-
Establish two-way voice communication
with local a.m. station to which radio
set is tuned. Check to see that trans-
mitted signals are received clear and
audible. Be sure that sidetone and
received signals are clear and au-
services chart once each periodic interval in ad-
4-8. Periodic Preventive Maintenance Checks
dition to the intermediate preventive mainte-
nance checks and services. The periodic preven-
Perform the preventive maintenance indicated in
the periodic preventive maintenance checks and
tive maintenance should be performed every 100