SG-2000 MANUAL
87
The SGC Building, 13737 S.E. 26th St. Bellevue, WA. 98005 USA
©1995, SGC, Inc.
TEL: (206) 746-6310 FAX: (206) 746-6384
In other words, unless you are planning extraordinary abuse of a vehicle, a shock
mount is not necessary. But if you run back country roads with 5 inch deep
chuck holes which cause a vibration factor over 3, a shock mount is required.
In addition to shock and vibration considerations, the mobile environment brings
with it two additional issues which need to be addressed before satisfactory
operations will be attained.
One is the ground system; the other is ignition noise.
14.2
Mobile Grounds
“They don't build 'em like they used to” is certainly true about today's auto-
mobiles. Not only do they have more wires, which can pick up stray RF, but
there are also generally fewer welds which means the ground system presented
by the vehicle may not be of high integrity. As a result, ground loops may occur,
and in some situations, reduced radiation efficiency due to a smaller ground
system. Here are some guidelines which will eliminate some ground issues.
1.
Keep all wire runs as short and direct as possible. This means keeping the
path direct. It is especially important to keep the antenna wire from the
SG-230/SG-235 coupler as short as possible to the external mobile antenna
(the SG-303 is recommended). Because the hot wire off the antenna
coupler terminal is where the antenna begins, if you have 12" of antenna
wire inside the vehicle, and you are using a 9 foot whip, 10% of your
antenna is inside the vehicle where it will not radiate and will be
susceptible to noise from vehicle systems.
2.
Use the largest wire size practical for power wiring. SGC recommends
that power lines from the battery to the radio be at least #6 gauge
stranded wire and that the ground of the battery be cleaned periodically
to make as good a connection as possible. Wire runs will cause loss. SGC
does not recommend any 12 VDC run of more than 25 feet.
3.
The ground from the radio chassis, from the coupler ground post, and
from the battery minus terminal should all be attached in two places,
preferably using braised wire of #0. The connection to the vehicle chassis
should be cleaned of paint and should be scraped to reveal raw metal. If
corrosion is likely to be a problem, you may fasten the ground system
very tightly using self tapping sheet metal screws and large copper
washers (to give maximum surface contact) then lightly dust the area
with Krylon™ matte finish or other clear varnish type finish to provide
some corrosion protection.