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OPERATION
AFTER THE AMPLIFIER TO MEASURE POWER! IT IS EASY TO EXCEED LEGAL LIMITS
AND FAR EXCEED THE RATED LIMITS OF THE HF5B BY DOING SO.
The HF5B operates as a two element beam antenna on 10, 12, 15, and 20 meters. On 17 meters only the
driven element is active, and the element operates as a dipole. The direction of maximum signal on 10,
15, and 20 meters is off the driven element, with the second element acting as a reflector. On 12 meters
however, the second element is self-resonant above the driven element and acts as a director. Therefore,
maximum signal on 12 meters is off the back of the antenna. Because the second element is not in the
circuit on 17 meters, the driven element alone is active on that band, and no "front-to-back" will be
observed, although there will be noticeable "front-to-side" difference in signal strength.
There are no high impedance "traps" used to isolate sections of the elements in the HF5B design. As a
result, the entire element is active on all bands, except for the reflector, which is not used for 17 meter
operation. The U-shaped stubs and 3/8 inch tubes provide variable inductive reactance on their
respective bands, while the capacitors contribute fixed capacitive reactance on their respective bands.
The values of reactance are chosen to allow simultaneous resonances of the element on five bands
without the need for external tuners or mechanical switching. On 12 and 17 meters, the rod and coil take
the place of U-shaped stubs to provide the necessary inductive reactance. Impedance matching to the
short element on 20 meters is accomplished by placing a coil across the feed point. Fine tuning for the
best match is accomplished by compressing or expanding this coil slightly. To achieve maximum
bandwidth, the element "diameter" is increased by terminating the element in 6 foot spreaders and
connecting the spreads tips to the element’s center with the twisted wires.
Although the elements are only 12 feet 6 inches, efficiency is maintained by using the entire element
length and high-Q circuitry. Therefore, performance compared to a larger two-element beam is barely
compromised. Gain, front-to-back ratio, and front-to-side ratio are maintained in comparison to larger
beams, assuming the dual requirements of adequate operating height and a clear "field" are met. The
major compromises in a short antenna like the HF5B are a narrowed SWR bandwidth and a limited power
handling capacity.
CUSTOMER SERVICE
For service, please write to us including ALL PERTINENT INFORMATION. This means SWR
CURVES, COMPLETE DESCRIPTION OF YOUR INSTALLATION, AND DESCRIPTION OF
SYMPTOMS.
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