64
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 pro-duct, you may from time to time find an antenna length which
just wonÕt quite work right. Generally this occurs when the Smartuner is
having 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 check-out 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
money by expecting the fiberglass hull to act as an insulator and not using a
lower insulator. The hull is not a good insulator and a thin layer of wet salt
water will degrade the ground further. Similarly, mobile HF users who rely on
a poor quality ball-mount find these are especially prone to arc over inside
the ball mount where it is difficult to detect.
The point we are making here is simply this: you should have a leakage path
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
© 1998 SGC Inc
SG-230 Manual