Instructions: AMB_BKT_1-T©
www.repDesign.us
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Version: 20120725
b) For V/UHF (6m and above), the counterpoise (groundplane radials) are connected to the ground point bolt near the
antenna base and works best if slightly shorter than a 1/4 wavelength. For single band antennas, the length should
be "cut" for the band; for multi band antennas cut the radials for the lowest band. These can be made from stiff
wire or whip antennas or other radials sticking out from the base of the antenna. Four are recommended, and can
be approximately horizontal or sloping away from the antenna at up to a 45 degree angle. Our "NMO radial base”
includes removable groundplane radials for 135-512 MHz.
5) Some antenna and coax suggestions.
Coax connection. Generally, RG-58 size coax works fine for portable or fixed-base installations where the length
of the coax is typically less than 25 feet, especially if you run under 500 watts. You can use any coax you desire.
SWR adjusting device (if needed) for HF antennas, especially those mounted near the ground, to reduce the SWR
to an acceptable level at the antenna resonance point on 160m and 80m, and maybe also on 40m. You may need a
shunt load inductor, UNUN, or additional capacitance to reduce the SWR. Some of these devices need to be
installed at the antenna and if so should be weather resistant (like our SHUNT-100).
Ferrite bead filters to reduce HF antenna tuning problems and to help prevent RFI in devices connected to your
radio. For the HF bands, use Mix 31 or other types that are designed to filter the entire HF band. Do NOT use
unknown ferrites as they may not work at HF frequencies! You may want to install at least 3 ferrites, closely
spaced, over your coax / antenna motor cable as close to your antenna as possible. One of these should have the
coax wound 2-3 times around one of the ferrites (improves filtering at the lower frequencies). Also install ferrites
in a similar fashion on your motor/turns counter cable, and install one ferrite on the coax near your transceiver.
Some installations may require 10 or more ferrites on EACH cable, at the antenna end of the cables. A white paper
on this topic can be downloaded for free from our web page: http://www.repdesign.us/Download.html
Tuning an HF screwdriver / motorized antenna. You can tune your antenna using a DPDT, center off, manual
switch or one of the automatic tuning devices that powers your antenna motor and stops at the resonance point. Do
not confuse these with "antenna tuners", which add capacitance / inductance to match the antenna to the radio -
generally speaking these should NOT be used with "resonant" antennas except to fine tune an SWR that is slightly
too high and can not be reduced by improved grounding, improving the ground counterpoise, installing ferrite
beads or using a load inductor or other device.
Using untuned "whip" antennas as the vertical antenna radiator. You can use a "CB" whip which would only be
resonant on 11-10 meters. To operate other bands you will need some type of antenna tuner mounted directly
below the whip.
Spare parts, accessories, downloads and related products.
Let us know if you need spare parts or are looking for something that we do not yet provide –your idea could become a
new product! As a specialty company, we are looking for unique ideas to serve the amateur and two-way radio community.
Warranty Summary
All products include a two (2) week "return for any reason" and six (6) month manufacturing defects limited
warranty. If you should need to return your product please contact us IN ADVANCE to obtain a return
authorization number. Please refer to the complete warranty terms that are enclosed with your order; this is also
included on our web site.
