Revised 14 June 2003
E-6
Antenna Settings for 2D-40A Mounted at 140 feet
(one full wavelength)
Frequency
(MHz)
Delta
(inches)
Tip Length
(inches)
6.948
0
50.5
7.015
-5
45.5
7.084
-10
40.5
7.154
-15
35.5
7.224
-20
30.5
7.296
-25
25.5
Fig 3-E
Tip Lengths vs Frequency (140 Feet)
If the antenna is to be installed at this height (approximately one wavelength), the sliding
shorts used to adjust tuning and matching for the array should be preset as follows:
The
tuning
(rear) shorting bar should be set to a distance of 25.3 inches back from the
element end of the parallel line on which the shorting bar slides. Note that this distance
is to the center of the shorting bar and does not include the length of the straps that
connect the parallel tuning line to the element.
The
matching
(front) shorting bar should be set to a distance of 39.75 inches back from
the element end of the parallel line on which the shorting bar slides. Note that this
distance is to the center of the shorting bar and does not include the length of the straps
that connect the parallel tuning line to the element.
All of the above adjustments apply only to an antenna which has element half-lengths
(center of boom to end of element
without the tip installed
) of 358.5 inches for the
front element and 386 inches for the rear element. If your antenna's element half-lengths
not including the adjustable tip section
differ from these values, please consult the
factory.
The tune-up procedure to use for an antenna mounted at 140 feet is exactly the same as
shown above for 70 feet. But the starting settings for the tuning shorts and the element
lengths for a particular frequency should be taken from Figure 3-E rather than from
Figure 2-E.
