In working through the logical troubleshooting process with him, we discov-
ered 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 capacitance 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 installation
worked fine.
Experiences like this have taught us to be fanatical about using the shortest
possible wire and no coax on the output of the coupler.
Another key lesson here is that even if you have a low capacitance lead, a
high capacitance antenna will not work well. If you have a whip type anten-
na, mounted on the back of a van, you will have a large portion of the antenna
running right next to grounded sheet metal. This causes a high loss to ground,
one reason why we do not recommend CB type whip antennas. The other rea-
son is the base insulation in ball mounts is inadequate for everything but
extremely low power.
L
L o
o n
n g
g ll e
e a
a d
d ll ii n
n e
e s
s .. If you have a Smartuner feeding a 9-foot antenna with a 1-
foot feed line located inside a hull or inside a vehicle, you have 10% of the
antenna where it will do you no good. If you have more than 5% of the anten-
na inside a grounded cabin, you will begin to lose performance.
A good rule of thumb is that under one foot of feed line is a good installation,
one to two feet aren't very good installations, and over two feet means you are
asking for trouble.
Ò
Ò O
O d
d d
d r
r e
e a
a c
c tt a
a n
n c
c e
e .. Ó
Ó The next category of antenna fault is what we call the Òodd
reactanceÓ problem. Although the Smartuner is an exceptionally well
designed product, you may from time to time find an antenna length which
just wonÕt quite work right. Generally this occurs when the Smartuner is hav-
ing a tough time making up its mind about which of two tuning solutions is
better. If it is a very close call, you can have an antenna which causes cycling
and just won't stay locked.
The solution in such cases is to add or subtract a couple of feet of wire from the
antenna. This generally cures the problem.
As part of your checkout of an HF system, you should operate on all channels
and frequencies which you plan to use on a regular basis to insure the coupler
and antenna which you have provided work well.
A
A n
n tt e
e n
n n
n a
a II n
n s
s u
u ll a
a tt o
o r
r. Sporadic operation may be caused by poor antenna
insulators. We have seen on sailboats, for example, people trying to save
65
© 1998 SGC Inc
SG-235 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