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||The Multee Antenna
Two-band operation may be obtained on 1.8/ 3.5 MHz or on 3.5/7 MHz
within the confines of the average city
lot by using the multee antenna . Dimensions are given for either pair
of bands in the drawing.
If built for the lower frequencies, the top portion will do little
radiating on 1.8 MHz; it acts merely as top loading
for the 52-foot vertical section. On 3.5 MHz, the horizontal portion
radiates and the vertical section acts
as a matching stub to transform the high feed-point impedance to the
coaxial cable impedance.
Since the antenna must work against ground on its lower frequency band,
it is necessary to install a good ground system.
Minimum requirements in this regard would include 20 radials, each 55 to
60 feet long for the 1.8/3.5-MHz version
or half that for the 3.5/7-MHz version. If not much area is available
for the radial system, wires as short as 25 feet
long (12 feet for 3.5/7-MHz) may be used if many are installed, but some
reduction in efficiency will result.
With suitable corrections in length to account for the velocity factor,
300- TV twin-lead may be substituted
for the open wire. The velocity factor should be taken into account for
both the vertical and horizontal portions
to preserve the impedance relationships
ARRL Antenna Book