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The SG-235 is supplied with a standard 25 feet of cable.
If necessary, the coupler can be installed up to 100 feet from the transmetter.
However, SGC does not recommend installing the Smartuner more than 100
feet from the transmitter because two losses must be considered.
¥ The first loss in long distance installations is normal attenuation of
the radio signal coming from the transmitter to the antenna via the coax. (The
longer the coaxial cable run, the higher the loss.) The amount of loss depends
on frequency. At 2 MHz, the loss is approximately .5 dB, while at 30 MHz the
loss in 100 feet of coaxial cable is over 2 dB. (A 100 watt transmitter at 30 MHz
would actually deliver about 70 watts to the antenna after running through
100 feet of coax.)
If you are seeking the utmost performance at 30 MHz and you cannot avoid a
run of 100 feet, or longer, we recommend using a larger low-loss type of coax
such as RG-8 (foam dielectric) or Belden type 9943 coax. Both of these will re-
duce attenuation to under 1 dB per 100 feet at frequencies below 30 MHz. You
should be aware that this heavier cable is less easy to work and may be quite
expensive.
¥ The second loss which must be considered is that in the DC power and
reset control line. At any distance other than the 25 foot cable which is sup-
plied by SGC, we recommend that the DC voltage at the antenna coupler be
measured. (If the coupler voltage drops below 10 volts, the coupler may not
operate properly.) For this reason, SGC recommends that if distances are
great, the input DC voltage at the transmitter site be adjusted to provide for +12
to +14 volts at the coupler site.
We do specifically advise against use of a different power supply than the one
used to power the radio because of the danger of creating ground loops.
Ground loops may cause oscillation of the final amplifiers or other undesired
side effects. If you decide to use a separate power supply mounted at the anten-
na coupler location, please be advised that SGC does not provide technical sup-
port in this area.
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-235 Manual