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The following is my opinion based on 8
years of ownership. Please follow the instructions and cautions detailed
in the SGC manuals.
The SG-235 antenna coupler is the
companion antenna tuner for the amplifier. The amplifier operates
into a 50 ohm load while the tuner will match antenna feed point impedance
from a wide range of antenna configurations. The SGC-235 operators manual describes a variety of land and marine
mobile antennas. Unlike conventional desktop antenna tuners, this
tuner is made for operation at the antenna feed point such as at the base
of a vertical, feed point of a long wire or dipole. It's water proof and the 12VDC power can be fed through
the coax with a few additional SGC options. SGC advises
shielding the tuner from direct sun and heat. The manual shows a
plastic bucket inverted over the SGC as a shield.
The tuner operates with little
noise, seems very fast, matches long wires over 50
feet in length and even longer ground radials.
CAUTIONS: The tuner is very RFI
sensitive as either will fail to begin to tune or will drop out during SSB
operation. Although the tuner is rated to run from 12VDC, I would encourage
13.5VDC. Read the following recommendations for reliable operation.
RESET is easy, simply remove DC and re-apply.
The SGC DC power injector blocks RF to
pass DC power to the tuner through the coax. Proper installation is
with the DC connections to the outside or away from the ends of the RF
coax.
On the average, the TUNED SWR is 1.2:1
or better, rarely higher.
Here are my recommendations for success
with this tuner when using the 80 through 10 meter bands. If 80 or 60
meters is not necessary, shorter radiator and ground plane wires are
possible.
The radiator should be at least 50 feet
#12 or larger stranded copper cable connected to the HOT output. A
larger diameter wire will lower the antenna Q and the feed point
reactance. A positive. If possible, I would try copper tubing
for the radiator. Best results have been obtained using a 35 foot
heavy duty AC extension cord.
A quarter wave counterpoise wire is only
valid above ground. When the wire touches the soil it is considerable
shorter. As an avid back packer, we use 31 feet for 40 & 60
meters. the ground radial should be at least
one length of #10 stranded copper cable connected directly to the SGC 235
large ground lug. A second length of 31 feet is almost
mandatory.
Pull the SGC coax straight away from the
tuner box, do not coil or wrap the coax or put coax near the tuner body
such as is possible in a portable emergency setup.
Install 5 to 8 Amidon
snap on type 31 ferrites around the coax/control cable about 2-3 feet AWAY
from the tuner box.
If the control box is removed, change
the internal jumper J-2 to NOT tune from memory. Another jumper on
the main board labeled PTT can be changed per your preferences.
Note that the SGC500 amp should be
disabled while tuning. Sometime in the future this function will be
automated but for now, the amplifier is switched OFF.
With these techniques, you will enjoy
many hours of operation.
Other: If the SGC fails to begin tuning
after about 5 seconds, remove the power to RESET and try again.
The SGC is a bit large to mount inside
my VW Westphalia so an original flavor LDG Electronics tuner is used.
I wrote a large post about wire antennas
on Yahoo Groups HFpack and encourage readers to
read the first 4 chapters of the ARRL Antenna Handbook. The handbook
contains information that applies to multi-band wire antennas. Topics
about feed points, wire length, on the ground radials and elevated radials
will improve SGC coupler performance.
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