The use of a CPI LABS HF dipole kit at just one end of the path--results in typical signal improvements of 15 dB or greater at 3 MHz. When used at both ends of the path (manpack-to-manpack), signal improvements of 25 dB or greater have been noted when compared with two whip antennas. Use of this antenna will often result in high-quality communications where no signals at all were present with whip antennas alone.
This ultra-lightweight, rapid-deployment, tactical antenna is compatible with all HF manpack radios. It is also suitable for base station use where portability is desired. Configurations available from this one kit are: Half-wave dipole, inverted "vee," NVIS, sloping dipole, vertical dipole, quarter-wave vertical with counterpoise, and long-wire with counterpoise.
No operator training is necessary. The antenna wire elements are precision calibrated with frequency markers. Both elements are simply unwound to the desired frequency as indicated. The antenna can then be connected to a pole, tree, mast, or building, etc. by means of the supplied nylon support lines and attached throwing weights.
Four different models are offered, all of which provide continuous frequency coverage between 30 MHz and a lower limit of 1.5, 1.6, 2 or 3 MHz. A full range of accessories is also offered.
QTY DESCRIPTION
2
Antenna element on winding spool
1
10 m (33 ft) RG58/U coaxial feed line
1
BNC center junction/insulator assembly
1
Nylon carrying bag
In addition, your antenna kit may include one or more of the following optional items:
10 m (33 ft) RG58/U coaxial
feed line extension
Halyard rope assembly on
winding spool
Long wire adapter
Broadband impedance matching
network
Ground stake
Before attempting operation,
make sure all necessary components are included, and if previously used--in
proper maintenance.
The dipole antenna can be setup in a number of different configurations, depending on the supports available and desired radiation pattern.
The following procedure is common to all configurations:
1) Locate an clear area with natural or man-made supports to hold the antenna up. Two end supports will be needed for a dipole configuration, while only a single support is needed for an "inverted vee" or sloping dipole. The clear area must be large enough to accommodate the antenna without any physical obstructions. The length of this area will depend on which configuration you choose, and frequency of operation.
2) Attach both antenna elements to the center junction unit, as shown in Figure 1. Connect the BNC coaxial feed line to the center junction.
3) Unwind both antenna elements until you reach the desired frequency marker. Loop the antenna wire through the slot in the winding spool, as shown in Figure 1.
NOTE: The desired frequency marker should be placed as close as possible to the slot. It can be located on either side of the slot-- towards the center junction or back on the winding spool. The exact location is not critical.
4) Completely unwind the end support ropes from each winding spool. Throw the end weights over the trees or other structures used as the end supports.
5) Pull on the end support ropes until the center junction is between 5 - 10 m (17 - 33 ft) above ground. Be sure to leave some slack in the ropes, so that any movement of the end supports (trees, etc.) in high winds will be accommodated. Tie the ropes off so the antenna remains fixed in place.
IMPORTANT!
When erecting the antenna, do not exceed 12 kg (25 lb.) of static
load on the end support ropes. It is normal for the center point
of the antenna to sag downward, which will not adversely affect performance.
Use of excessive puling force will put undue stress on the antenna wire
insulation and other components, possibly shortening their lifespan.
At frequencies under 2.0 MHz, the antenna wire element becomes exceptionally long. To minimize excessive physical stresses and sag at the center point, an "inverted vee" configuration should be used instead of a standard horizontal dipole (see Figure 3). This configuration will result in better RF performance, since the feedpoint (point of maximum radiation) is placed high above ground. In addition, the halyard support will relieve the antenna wire from excessive stresses and increase life span.
CPI LABS offers an optional
halyard rope assembly for the HF Dipole Antenna Kit, which fits inside
the carrying bag.
1) Horizontal dipole
configuration
2) Center junction
5 m (17 ft) above ground
3) Average soil conductivity
Since actual conditions of use may vary greatly, the frequency markers should be used only as a general guide to antenna length. If the resonant frequency is found to be higher or lower than desired, simply wind or unwind each antenna element a uniform amount to make the correction. This type of correction is most often necessary when using the "inverted vee" configuration.
If the resonant frequency
is correct, but SWR is excessively high, this condition may be caused by
the influence of nearby objects, especially metallic ones (buildings, other
antenna wires, telephone lines, etc.) Try installing the antenna
in another location or different orientation. The antenna may also
be connected to an antenna tuning unit (ATU) if a good match to the radio
cannot be obtained by any other means.
Mounting the horizontal dipole
higher causes the vertical radiation angle to tilt down, towards the horizon.
This will favor long-distance communications, 160 km (100 miles) or greater.
NOTE: The inverted vee configuration should always be used for operation below 2 MHz. Refer to Section 3.1 for further explanation.
When using the inverted vee, two characteristics must be noted:
1) The angle between the two halves must be maintained at 90 degrees or greater, to prevent cancellation of the radiation.
2) Frequency marker calibration may be slightly inaccurate, depending on the height of the antenna above ground and the angle between the two antenna halves. It may be necessary to re-adjust antenna element length to compensate for these factors.
The major radiation pattern
of the inverted vee is broadside to the direction of the wire, same
as the horizontal dipole. However, the inverted vee also exhibits
a minor radiation pattern directly in line with each end
of the wire. These minor radiation lobes are generally low in
vertical radiation angle, which are useful for long-distance communications.
The antenna can be oriented to make best advantage of this combination
radiation pattern.
When using the sloper, three characteristics must be noted:
1) The "plus" sign (+) on the BNC center junction unit must be connected to the upper half of the antenna wire. This will increase the efficiency of the radiation pattern.
2) Slopers exhibit mostly low-angle radiation, which makes them good for long-distance communications, but generally poor for short-distance skywave (NVIS) operation. Use the sloper only when long-distance paths are necessary.
3) The sloper will
exhibit approximately 2 dB signal gain in the direction of the sloping
wire. Conversely, it will exhibit a significant null in the opposite
or rear direction. This directional pattern can be used to optimize
signal strength in one favored direction, or to minimize interference coming
from an undesired direction.
sales@shortwaves.com E-mail
us for pricing and additional information
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Updated July 1998