Operator's Preventive Maintenance Checks and Services Chart for Coupler, Antenna CU-2004/U

TM 11-5820-554-12

p. As the transmitter frequency is moved about

m. If it is still impossible to obtain a unity swr,

in normal operating procedures, watch the swr, and

connect the antenna to the terminal marked SHUNT,

if it becomes excessive, begin the tuning procedures

and connect a jumper from the terminal marked

again.

SERIES to ground. Then repeat h, i, and k above at

q. A combination of ANT OUTPUT C and

the same tune adjusting ANTENNA OUTPUT C

SERIES COIL settings may optimize the minimum

along with the controls in h and i above.

reflected power indication.

A number of

n. If a unity swr cannot be obtained with any of

combinations of settings of the above controls may

the above combinations, the antenna impedance is

produce resonance. In general, the highest dial

probably beyond the range of the antenna coupler.

setting for ANT OUTPUT C producing resonance

However, the coupler should handle almost any

will produce the best results.

reasonable antenna with the exception of very short

r. Make a log of the settings for each frequency.

antennas at low frequencies (less than 1/8

If there are no changes in the antenna system, it

wavelength below 7 MHz). Where unity swr cannot

should be possible to return to a given frequency by

be obtained, use the minimum Swr that can be

setting up the dial numbers without having to go

obtained. If the swr cannot be made less than 2.5 to

through the entire tuning procedure.

1, the antenna length should be either increased or

decreased until a better match can be made.

12-5. Operator's Maintenance

o. Note that on the higher frequencies (20 to 30

Instructions

MHz), the setting of the various controls becomes

quite critical. When tuning adjustments are made,

Operator's maintenance instructions are covered in

adjust the controls slowly so that the proper setting

paragraphs 3-19 through 3-22. Cleaning is covered

will not be passed over too quickly to be noticed.

in paragraph 3-24.

12-6. Operator's Preventive Maintenance Checks and Services Chart for Coupler,

Antenna CU-2004/U

B-Before

Interval

Item

Item to be inspected

Procedure

Equipment is not

No.

ready/available if:

Rf connectors

Check for damage or corrosion.

Connectors cause SWR to be

unable to be corrected.

12-7. Organizational Maintenance Instructions

Organizational preventive maintenance instructions are covered in paragraphs 3-26, 3-26, and 3-27. Touchup painting is

covered in paragraph 3-29.

12-8. Organizational Preventive Maintenance Checks and Services Chart for Coupler,

Antenna CU-2004/U

W-Weekly

M-Monthly

Q-Quarterly

Interval

Item

Item to be inspected

Procedure

No.

Tuning unit.

Terminate tuning unit in dummy load. While

changing control settings observe VSWR. SWR

will remain constant. If not, check tuning unit

components.

Change 6 12-3