2182 kHz Shunt Fed Antenna Analysis
This antenna is designed for 2182 kHz (47 CFR 80.369.a). The tower is a Rohn 45G, that is shunt fed
with a 4" aluminium pipe separated at an exact distance to provide the appropiate inductive coupling. The radiation
pattern is omni-directional with a nice, low launch angle for the electromagnetic energy radiating from the antenna. The
tower is a quarter wave at the fundamental frequency. Thus, "unity" is achieved.
The question that we presented to the NEC 4 software was: If the antenna's shunt fed mechanisms were fed through a
tuner for a multiple range of frequencies, how would the antenna load? The only way to find out was the model the
antenna with the SSB radio frequencies used for distress communications. These frequencies are: 2182.0 kHz, 4125.0 kHz,
8291.0 kHz, 12290.0 kHz and 16420.0 kHz (47 CFR 80.369 (2)(b)).
The results were quite pleasing. Each of the frequencies all radiated omni-directionally at a low angle of radiation. However,
one variation was noted. There is some phasing of the signal on the 8 mHz frequency compared to the 12 mHz frequency.
The 8 mHz signal radiates 180 degrees away from the 12 mHz signal.
Please note, we are attempting to radiate a tower designed for 2182.0 kHz on frequencies not intended for its original
design. You can't have everything. However, it does radiate well when looking at the total picture.
We also modeled the 3023.0 kHz and 5680 kHz frequencies (47 CFR 80.1077(6)) on this same antenna. These two
frequencies are specifically designated for: "Land stations engaged in coordinating search and rescue operations."
The shunt fed vertical fed through a tuner exhibited omni-directionally (top view) with a low launch side angle (side view).
Both of these characteristics are desirable for long-range communication.
Malloy Communications supports the tower with Phillistran guying cable. Phillistran is a synthetic strand that has the
same tinsel strength as 1/4" high tension metal cable (6500 psi).
If you have any questions, please feel free to contact us.