Yaesu FT-920, Operating Manual, Page: 10 / 98

FT-920 Operating Manual
8
Transceiver Location
To ensure long life of the transceiver’s components,
be certain to provide adequate ventilation around the
cabinet of the FT-920. The cooling system of the
transceiver must be free to draw cool air in from the
side of the transceiver and expel warm air from the
rear exhaust port.
Do not install this transceiver on top of another heat-
generating device (such as a linear amplifier), and
do not place equipment, books, or papers on top of
the transceiver. Place the radio on a hard, flat, stable
surface. Avoid heating vents and window locations
that could expose the transceiver to excessive direct
sunlight, especially in hot climates.
Grounding
The FT-920 HF transceiver, like any other HF com-
munications apparatus, requires an effective ground
system for maximum electrical safety and best com-
munications effectiveness. A good ground system can
contribute to station efficiency in a number of ways:
r
It can minimize the possibility of electrical shock
to the operator.
r
It can minimize RF currents flowing on the
shield of the coaxial cable and the chassis of
the transceiver; such currents may lead to ra-
diation which can cause interference to home
entertainment devices or laboratory test equip-
ment.
r
It can minimize the possibility of erratic trans-
ceiver/accessory operation caused by RF feed-
back and/or improper current flow through logic
devices.
An effective earth ground system make take several
forms; for a more complete discussion, see an ap-
propriate RF engineering text. The information be-
low is intended only as a guideline.
Typically, the ground connection consists of one or
more copper-clad steel rods, driven into the ground.
If multiple ground rods are used, they should be po-
sitioned in a “V” configuration, and bonded together
at the apex of the “V” which is nearest the station
location. Use a heavy, braided cable (such as the
discarded shield from type RG-213 coaxial cable) and
strong cable clamps to secure the braided cable(s)
to the ground rods. Be sure to weatherproof the con-
nections to ensure many years of reliable service.
Use the same type of heavy, braided cable for the
connections to the station ground bus (described
below).
Inside the station, a common ground bus consisting
of a copper pipe of at least 25 mm (1”) diameter
should be used. An alternative station ground bus
may consist of a wide copper plate (single-sided cir-
cuit board material is ideal) secured to the bottom of
the operating desk. Grounding connections from in-
dividual devices such as transceivers, power supplies,
and data communications devices (TNCs, etc.)
should be made directly to the ground bus using a
heavy, braided cable.
Please note that some types of external power sup-
plies (not of Yaesu manufacture), while otherwise
being suitable for use with the FT-920, may be de-
signed such that the Negative (black) DC output ter-
minal is “floating” (not connected directly to ground).
This may cause erratic operation, especially when
transmitting, due to the potential for ground loops to
form between your antenna system, your station
ground, and your power supply. This potential sus-
ceptibility is not unique to the FT-920, and the prob-
lem can usually be solved by directly grounding the
Negative DC terminal to the power supply chassis,
which can then be bonded to earth ground; check
first with the power supply manufacturer, though, to
be certain that this grounding technique is accept-
able to them.
Do not make ground connections from one electrical
device to another, and thence to the ground bus. This
so-called “Daisy-Chain” grounding technique may
nullify any attempt at effective radio frequency ground-
ing.
Inspect the ground system — inside the station as
well as outside — on a regular basis so as to ensure
maximum performance and safety.