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2. Enhanced System: You may also install the MA160V over a more robust radial system (FIG-14B).
Benefits include a somewhat lower take-off angle plus higher radiating efficiency because of reduced ground
losses. In order to implement a larger system, you'll need more open space plus significantly more radial
wire than the 400 feet provided with the antenna. You'll also need to install some type of matching network
to compensate for the system's lower feedpoint resistance. The ARRL Antenna Book and many other
publications offer detailed instructions describing radial field construction and vertical antenna matching
techniques. Extra radial wire may come from any surplus source as long as it is jacketed or enameled and
strong enough to avoid breakage. Several matching options are possible including a shunt inductor, fixed-
ratio Ununn, transmission line transformer, or adjustable L-network. The best matching technique will
depend on factors like the transformation ratio needed and the amount of power you intend to run.
Generally, for a loaded antenna like the MA160V, a dense ground system with a large number of shorter
wires will perform better than a full-sized ¼-wave system with fewer radials. The layout described below
should work well. For best results, install as described:
[ ] Cut 16 primary radials of 50 to 60 feet in length.
[ ] Scrape or remove insulation at one end and install a #8 solder lug on each.
[ ] Lay these radials out in a symmetrical pattern around the base and connect each to the radial ring.
[ ] Check the feedpoint resistance with a handheld analyzer using the "vector impedance" function*.
[ ] Continue adding radials, filling in between the primary set, while periodically checking resistance.
[ ] If using a fixed-ratio matching transformer, add radials until you reach a convenient transformation value.
[ ] If using an adjustable network, add radials until you reach the point of diminishing returns (64 max).
* See notes below
Notes: When monitoring feedpoint resistance, disconnect the station feedline and connect the analyzer
directly to the antenna terminals through a short pigtail (making these measurements through a long feed
will transform readings to erroneous values). Also, note that shunt-coil matching systems will introduce
inductive reactance that lowers the system's resonant operating frequency. Readjustment of the stinger will
be needed to compensate for this downward frequency shift.
Housekeeping: When the radial installation is complete, inspect the base area for looped or hanging wires
that may pull loose or become broken at a later time. Trim or bury any excess (see FIG-14C). Also, confirm
that all radial ring screws are fully tightened.
Resonator Tuning: The telescoping stinger above the capacitive hat was designed to provide tuning over
the full 160 Meter band. However, tuning range may be impacted by external factors such as soil
conductivity, radial field irregularities, and proximity to other antennas or metallic objects. In the event you
experience difficulty tuning to the bottom of the band, attach a thin wire between the tips of two or three
capacitive hat rods to extend tuning range. Conversely, you may remove a hat rod to extend coverage at the
high end of the band.
FIG-14B: Example of High-Efficiency Radial System
FIG-14C: Dress Radial Leads, Check Hardware
Use
16 - 64
radials
of 50 to 60
feet each.
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