Specifications

SG-231 MANUAL
SGC Inc. SGC Building, 13737 S.E. 26th St. Bellevue, WA. 98005 USA
© 11/00 SGC, Inc. P.O. Box 3526, 98009 Fax: [phone] Tel: [phone]
E-Mail: [e-mail] Website: www.sgcworld.com
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Figure 4.5.11 Vessel insulated back stay
Radiation
75 feet
Porcelain
isolator
Vessel
insulated
Backstay
Ground
connection
Porcelain
isolator
Coupler
The insulated backstay antenna requires two porcelains isolators. The coupler must be
placed as close as possible to the base of the backstay antenna. Proper grounding of the
coupler is very important. Connect the RF ground terminal of the coupler to all of the
metal parts or structures of the boat (keel, engine, etc.).
4.6 Apartment Loop Antenna
Loop antennas can be used very effectively in small apartments, offices, and rooms.
Radiation for a loop antenna is always efficient but highly directive. Therefore, the
orientation of the loop is very important. Generally, the vertical loop antenna with
horizontal radiation is much preferred for a general application throughout the 1.8 to 30
MHz band. However, loop antennas can be effective when mounted horizontally to the
ground to radiate vertically and provide efficient short-range communications on
higher frequencies. Generally HF connections are difficult to establish in the distance
range of 50 to 250 miles. In a large room (such as 20 x 30), we would recommend the
installation of a single wire loop antenna mounted on the ceiling with the coupler
against the wall directly below the antenna. The wire gauge should not be less than 16
AWG with insulation.
When operating in a small room, install a small multiple wire loop (six loops) on a
rectangular configuration three by four feet (as illustrated in Figure 4.6.1). This
configuration allows operation from 1.8 to 60 MHz, and the SG-231 will tune and load
all frequencies well below a ratio of 1.4:1 VSWR. Directivity will be high from 3 to 12
dB depending upon the frequency. If this is a problem, two loops at 90 degrees can be