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Running of the power leads inside a steel conduit is highly
recommended to obtain both audio and radio frequency shielding
near the transmitter.
To assist in keeping RF currants in nearby audio equipment te
a minimum,
a good ground at these frequencies is mandatory.
One of the best known methods of doing this is the installation
of a sheet of copper or a ground system beneath the complete
transmitter layout.
RF usually shows up in one of two ways,
feedback or high noise,
or both.
It should be pointed out that
even a small amount of unshielded wire makes a vary efficient
antenna at FM frequencies,
for transferring RF to the grids whore
it is rectified and passed on as noise and feedback.
It is
preferable to have a single common ground point from the trans-
mitter copper shield to a good ground.
Since heat
is developed in the transmitter,
it will be necessary
to provide a means of exhausting air expelled through the top
outlets of the unit to the outside.
An air duct leading to the
outside should be provided,
and provisions made for utilizing
this heat in the winter if desired.
There are several kilo-
watts of heat dissipated,
and if allowed to recirculate back
through the transmitter, the forced air coeling will become very
inefficient and can causo damage to tubes and other co;Iponents.
The duct work where the transmitter is used should not intro-
duce any back pressure.
UN2ACKING AND RIi;ADYING FOR OPERATION
The FM-20Bis carefully checked and packed at the Gates plant to
assure its safe arrival at its destination in proper mechanical
a
nd electrical condition.
Tests of many different kinds are made at the factory,
and the
unit is operated for several hours on the customer's operating
frequency to assure correct adjustment of proper operating con-
ditions.
Immediately after the FM-20Bhas been received and unpacked it
should be carefully checked for mechanical damage.
If damage
is noticed in any section of the equipment a claim should be
filed immediately with the delivery transportation company and
the necessary replacement parts ordered from the Gates Radio
Company.
It is good precautionary practice to completely go over the
equipment to check for loose connections,
loose components,
broken insulators,
etc.,
that might have become.loosené'd or
damaged in shipment.
Make sure all relay contacts are free and
in good mechanical operation.
Make sure all mech
n
nicgl connec-
tions ara tight,
The power contactors are either tied down or
blocked sufficiently to keep them from vibrating during ship-
ment.
These should be checked and the shipping material re -
6/22/61
-5-
FM- 20B
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