Maintenance
38
Keep an eye on dry gas usage. A sudden increase in usage indicates a leak in
the system. Troubleshoot per
Chapter 8
.
De-Icer Check
Periodically (we suggest at the end of each winter season), check the condi-
tion of the de-icer wiring with an ammeter; compare the legs of the system
with each other and with initial readings taken at installation. If an ammeter is
not available, resistance readings of each leg will suffice.
Paint
The radiators should never be painted (a coating of paint affects VSWR), and
they need no surface protection, since they are made of copper and brass.
This includes Teflon or other "ice-prevention" coatings.
It is not necessary to paint the feedline, although no harm will result from
doing so.
Radiator Removal for
Repair
If a radiator is damaged, it may be removed and returned to the factory for
repair. The system can then be sealed with a pressure cap, and operation of
the antenna can resume with proportional power reduction and increased
VSWR.
CAUTION
Operating with missing bays may not be possible with some transmit-
ters or antennas that have only a few bays, since some transmitters will
not operate into loads with high VSWRs. If in doubt, contact your sales
representative at Shively Labs.
For example, the removal of one radiator from a six-bay antenna that has
been trimmed to a VSWR of 1.05 : 1 or less will cause the VSWR to increase
to 1.2 : 1. The gain will drop to 83% of its former value. Power output should
also be dropped to 83% of normal output.
NOTE
O-rings and flange hardware are provided as spare parts with every
antenna. If a new O-ring is not available, the used one may be reused
temporarily; lubricate it with a light coat of petroleum jelly when rein-
stalling it, and replace it with a new O-ring when replacing the radiator.
Remove a radiator as follows:
a. Release gas pressure.
b. Remove the radome if applicable, and the radiator, in the reverse sequence
of installation (
Chapter 2
and
Chapter 3
).
CAUTION
When installing a pressure cap on a baymount flange, be sure that the
pressure cap is recessed to clear the feedline inner conductor.
c. Reseal the baymount flange with a standard-size pressure cap. If you don't
have a pressure cap to fit this system, call Shively and we'll rush you one.
d. Re-purge the system after removing or replacing a radiator (or any other
time its seal is broken). If the exposure is brief and in clear weather, a purge
of one volume should be sufficient (see
Purging the System
on page 25).
e. Operate the system with power reduced in proportion to the bays removed.
