DX Engineering 4-BTV, Руководство по установке

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Chapter 9 - Reference Information
Elevated Mounting of the Hustler
®
BTV Antenna 49
The Quarter-Wave Vertical on a Metal Roof 50
What Trap Do I Have? 52
Hustler
®
BTV Replacement Parts Diagram 53
Weatherproofing Coaxial Cable Connections 54
Lightning Protection - For Any Installation 54
Hustler
®
BTV Specifications 55
Elevated Mounting of the Hustler
®
BTV
In some situations, an elevated or roof-mounted vertical installation is the only option. Elevated
installations are more difficult. In all but certain metal roof elevated installations, resonance-tuned
radials must do the job of collecting RF currents. Imagine all of the quarter-
wave resonant length wires attached to the base of the antenna, spreading
radially (away from the base of the vertical in all directions). For best DX
performance, these radials should slope down from the vertical at a 45
degree angle. You can connect the ends of the long radials to support poles
or trees. Use the same care as you would for a dipole antenna, keeping the
ends insulated and clear of any metal. We recommend four resonant radials
per band to enhance low angle radiation. If you must elevate your antenna,
Pre-Cut Radial Wire Sets are also available from DX Engineering.
An antenna analyzer such as the MFJ-259B or an SWR meter is used to make resonant, elevated
radials. For the Hustler
®
BTV series and most other quarter-wave vertical antennas, it is best to start
with the highest band, usually 10 meters. Determine the frequency within the 10 meter band where
you want the vertical to resonate. Construct two radials, as if you were making a dipole, to resonate
on that frequency. Next, make two more radials the same length. Then, connect all four to the base
of the vertical or the Radial Plate. Fan them out symmetrically from the antenna.
Using the information in Chapter 7, tune the 10 meter section of the vertical for the lowest SWR on
the same frequency as your radials. Repeat this procedure for the remainder of the bands your
antenna covers, going from the highest frequency band to the lowest frequency band. In an elevated
vertical installation, do not ground the radials, the mast, or the vertical mount. Grounding them will
probably detune your resonant radial system!
Be careful - The vertical will be high above the ground, be aware of any overhead power lines that
may touch the vertical antenna or radial wires. The vertical should be at least its own height plus 10
feet away from any wires or obstacles so if it falls, it cannot come in contact with electrical power
lines (remember the 10 foot safety rule). Contact with power lines can be fatal! Proper guying of
your elevated vertical requires planning. Find good guying anchor points before installing your
antenna.