12.2m
9.1m
3m
~
"A" Models
TO TRANSCEIVER
ANTENNA PORT
/ r[H~'INAliON
r~N~~~,~~Cp~:~~R'-
RECTANGULAR CONFIGURATION
DELTA CONFIGURATION
Fig. 1.
Fig. 2.
3m
----L
"8" Models
DIAMOND CONFIGURATION
INSTAllATION CONFIGURATIONS
The recommended mounting
configuration is a Delta Loop as
shown in Figure 1. Alternative
configurations such as shown in
Figure 2 may also be used. The
efficiency with alternate mounting
arrangements remains essentially the
same as long as the total wire length
is maintained and the aperture of the
antenna is kept as large as possible.
For example, we do not recommend
erecting the antenna in the Delta Loop
configuration with shorter center
masts than those shown in the
diagrams. Because of the reduced
aperture at the two ends, the radiation
efficiency would be much lower.
Regardless of the mounting
configuration, the recommended feed
point for the antenna is at the top
center. This keeps the maximum
current and maximum radiation at the
highest point in the antenna. The load
is located at the bottom and can be
mounted on the center mast.
EFFICIENT DESIGN
One of the secrets of the new
antennas is the special balun that
transforms the 50 ohm coaxial feed
impedance to 800 ohms over the
entire HF range. A special dual
transformation balun is used that
provides an efficient broadband
transformation and is rated for
continuous operation at 1000W. The
load resistance is 800 ohms and the
100W load is constructed from series
connected 5W non-inductive resistors
mounted in a weatherproof tube. The
kilowatt load uses three 250W 17
ohm non-inductive wire wound
resistors mounted on a heatsink and
a second balun is used to make the
down transformation to 50 ohms.
We have been able to use the 50
ohm down transformation on the
kilowatt antenna to make direct
efficiency measurements. A
wattmeter was connected in series
with a 50 ohm load so that the power
dissipated in th5l load could be
measured directly. If the small losses
in the balun and wire resistance are
neglected, this gives us a direct
measure of the efficiency of the
antenna system. We found that the
maximum loss (at 2MHz) was 5.6dB
for the shorter antennas and 4.5dB
for the longer model. At 8MHz the
efficiencies of both models were
similar with losses of about 3dB.
Above 10MHz losses are very small,
ranging from 0.5 to 2dB.
The high impedance of the antennas
has enabled the use of 1/16 inch
(1.6mm) stainless steel cable in place
of copper wire. The additional
resistance introduces negligible
losses but the resulting antenna is
exceptionally strong and should not
deteriorate even under severe
environmental conditions.
RADIATION CHARACTERISTICS
Our field tests show that the antenna
is an excellent performer for short or
medium ranges. When the antenna
length is close to a half wave dipole,
the performance and radiation
pattern is very similar to the dipole.
As the frequency increases the
radiation pattern follows the pattern
of a long dipole. Lobes develop off
the ends of the antenna and at the
top end of the range the radiation
pattern will change from broadside to
end-fire with some gain and directivity
when compared with a dipole. While
a half wavelength resonant dipole will
outperform this antenna, the
difference in performance will be
difficult to measure over short to
medium distances. We recommend
the new antennas for ranges up to
2500 Km.
The antennas are supplied partially
assembled (for ease in shipping) and
are complete with all material except
masts. All antennas are supplied
complete with 30m (100 ft.) of RG213
coaxial cable and the appropriate
connector installed (PL259 or Type N,
as required). An optional mast kit is
also available.
25
20
ill
!2.'5
'"
'"
'3
z
a:
:J1O
tu
a:
5 10
FREQUENCY (MHz)
VSWR ABB 100
Specifications subject to change without notice.
25
20
ill
~5
'3
z
a:
~10 __
a:
25
20
30
5 10
FREQUENCY (MHz)
VSWR ABB 1000
30
20
10 15 20
FREQUENCY (MHz)
EFFICIENCY ABB 1000 A
30
& B
PL 3/89
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