8
THEORY OF OPRATION
resonance.
In order to minimize conductor and IR losses on 80 and 40 meters where the antenna is physically shorter
than a quarter wavelength and thus operates with lower values of radiation resistance, large diameter self
supporting inductors and low loss ceramic capacitors are employed.
Because the 20 meter radiation resistance is several times greater than that of conventional "trap" designs
of the same height, an electrical quarter wavelength of 75-ohm cable is used as a "geometric mean"
transformer to match the approximately 100 ohms of the 20 meter feedpoint impedance to a 50-ohm
feedline of any convenient length.
If operation is desired on 160 meters, the 17 and 12 meter bands, or even 6 meters, add-on kits requiring
no "surgery" are available from your Butternut dealer. NOTE: The A-17-12 and A-6 adapters are
provided with the HF9V-X.
ELECTRICAL AND MECHANICAL SPECIFICATIONS
Shipping weight: 12 lbs/5.4 kg (HF6V-X) 14 lbs/6.4 kg (HF9V-X)
Height (adjustable): 26 ft/7.8 m
Feedpoint impedance: nominal 50 ohms with included matching line
SWR at resonance: 1.5 or less—all bands
SWR bandwidth for 2:1 or less: entire 10, 15, 20 and 30 meter bands; 250-300 kHz on 40 meters,
30-100 kHz on 75/80 meters
Power rating: 1500 watts PEP 80-10 meters; 400 w PEP on 30 meters
Wind loading area: 1.5 sq ft/0.15 sq m
GUYING
The antenna is designed to survive winds of up to 80 mph/125 kph without guying given the absence of
ice-loading or heavy wind driven rain or sleet. In areas of frequent heavy winds a set of SHORT guys
can be used to reduce the stresses that wind loading will impart to the lower sections of the antenna.
It should be noted that light nylon twine is totally unsuitable as guying material because it has too much
stretch per unit length, although the heavier sizes of nylon rope (or even sash cord) may be suitable if
used in short runs. Polyethylene rope may be used, but because some grades tend to deteriorate fairly
rapidly, periodic inspections should be made.
A single set of guys placed just above the 30 meter circuit will be quite effective, provided that the guys
retain a slight amount of slack and do not come off at too steep and angle. At angles of less than 45° the
guys begin to exert a downward compressive force on the structure that can be more of a threat to
survival than lateral wind loading on an unguyed structure.
Under no circumstances should guys be placed higher than 1/3 of the way up the antenna. The upper 2/3
of the antenna has little more than its own weight to support, so these sections may be allowed to bend
with the wind with no serious risk of damage. It is the lower 1/3 of the antenna that must support both
the weight of the upper sections and the wind loading on them and are thus more likely to receive damage
in severe winds.
