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Chapter 7 - Tuning
Understanding Trap Calibration
43
Hustler
®
Traps
44
Hustler
®
Trap Calibration - Resonance Adjustment Procedure
46
Tuning the 80 Meter Resonator Whip for the 5-BTV and 6-BTV
47
Understanding Trap Calibration
The Hustler
®
warranty states that adjustment of the traps will void the warranty. As described in this
manual, trap adjustment is usually required. When you purchased your Hustler
®
BTV from DX
Engineering, your warranty is safe.
Trap calibration adjustment will NOT void the warranty of a Hustler
®
antenna purchased from
DX Engineering. The antenna traps will not be harmed by performing this tuning procedure.
Note: For the purposes of these instructions the term “resonance” or “resonant frequency” is
defined as the point of lowest SWR and may be used interchangeably.
A high efficiency quarter-wave vertical requires a good radial system. Installations with few or no
radials are inefficient due to high ground losses. These losses are the reason that verticals with no
radials or few radials seem to exhibit a great SWR curve, which is a sure sign of an inefficient
vertical antenna. Therefore, removal of radials to achieve a lower SWR, or a broader SWR curve, is
not a tuning solution. DO NOT attempt to tune the vertical antenna by changing radials in any way.
A
fter Installing a Good Radial System, the Hustler
®
4-, 5- and 6-Band Trap Vertical
antennas, as supplied by the manufacturer, will normally resonate at frequencies much lower
than desired, and especially when installed on very good soil, saltwater or a metal roof.
Readjusting antenna resonance is easy. The traps were made to be adjustable so that retuning the
vertical for in-band resonance is not difficult. The trap sleeve position adjustment may be done the
same as on other parts of the antenna. You can loosen the stainless element clamp, make a trap
sleeve adjustment and tighten the clamp. Note that a slight movement of the trap sleeve will
produce a rapid change in the frequency of lowest SWR. Follow the procedure described below
carefully to make large frequency adjustments to any Hustler
®
BTV HF antenna.
Never Cut the Aluminum Tubing
-
You cannot properly adjust the frequency of the Hustler®
BTV antenna by cutting the traps or by cutting the aluminum tubing above or below the traps.
The right tool for the job -
An antenna analyzer is the best tool to use for adjusting any antenna
to the target frequency if it is connected directly to the feedpoint. Since that is never convenient,
use a six foot piece of 50Ω coaxial cable between the antenna and the analyzer and tune for
minimum SWR. Your body can affect the tuning if you are too close to the antenna. If the coaxial
cable length is too long, the analyzer SWR measurements may be incorrect.
When adjusting antennas, your primary goal is to move the low SWR point to your target
frequency. [Perfect analyzer impedance readings near 50 Ω resistance and X=0 or ±
j
0 reactance
