Particularly in automobiles and aircraft, a single ground connection
w
w ii ll ll
n
no
ott d
do
o. It is mandatory that at least two ground bolt connections are used.
II n
n a
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c c
c u
u r
r a
a tt e
e a
a s
s s
s u
u m
m p
p tt ii o
o n
n s
s .. The fifth situation to check for is what we call
Òdangerous assumptionsÓ about the ground system. When you bond from the
antenna coupler to copper or iron water pipes, you might make an assump-
tion that the water pipes are a good ground. But in many installations,
copper pipes are used in the building but a plastic main connects to the
municipal system outside the service entrance. So much for a good ground.
1
10
0..2
2 A
An
ntte
en
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na
a F
Fa
au
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s
The key to getting the most out of your Smartuner is to realize the antenna
begins right at the high voltage screw on the SG-230 case. In other words,
this is the feed point of your antenna system. Failing to install your coupler
accordingly will result in unsatisfactory operation. With this concept in
mind, you can easily avoid some of the common troubles with a properly
planned installation.
C
C o
o a
a x
x ii a
a ll c
c a
a b
b ll e
e o
o n
n o
o u
u tt p
p u
u tt .. Coax on the output is probably the single most
commonly asked question about the coupler and is the most misunderstood.
Let us reiterate: The Smartuner was not designed to feed a piece of coax.
S
S tt r
r a
a y
y g
g r
r o
o u
u n
n d
d c
c a
a p
p a
a c
c ii tt a
a n
n c
c e
e .. Stray ground capacitance is the next largest
cause of malfunctioning installations. If you have a long lead wire from the
coupler to a feed-through (on a wall or bulkhead), you significantly
increase your chance of problems. Wire running parallel to a grounded
surface may represent a significant capacitance to ground and, just as with
coax, this will cause problems.
To give you an idea how these two points can cause problems, let us relate an
incident which happened in late 1992. A Smartuner user had a coupler
installed in a mobile ham radio installation. The coupler could not find a
lock on several bands. After going through his installation carefully, the
user called SGC for technical support. This user was nearing wits end.
In working through the logical troubleshooting process with him, we dis-
covered that he had used coaxial feed line from the insulator on the coupler
to the antenna feed point. Because he had read about the dangers of capaci-
tance to ground in an earlier edition of this manual, he did not have the coax
shield grounded. We had him remove the ungrounded braid and the instal-
lation worked fine.
63
© 1998 SGC Inc
SG-230 Manual
SGC Inc. SGC Building, 13737 S.E. 26th St. Bellevue, WA 98005 USA
P.O. Box 3526, 98009 Fax: 425-746-6384 Tel: 425- 746-6310 or 1-800-259 7331
E-mail: [email protected] Web site: http://www.sgcworld.com