Hello Top Banders,
I usually just lurk here, but thought I'd share a little info on my
approach to operating 160 M mobile.
I built a multi-band HF station in a 2006 Toyota Tacoma truck that has
served me well since 2006 on the top band. Primary use has been in the
WA State Salmon Run contest. The station was built as follows:
I ripped out the plastic storage compartments behind the rear seat of a
double cab Tacoma and installed a 1/4" Al plate to vertically mount the
main radio, amplifier and power distribution components. A second
glass-mat type deep cycle battery was also installed behind the rear
seat and linked to the front battery with 00 gage welding cable and a
200 amp smart solenoid. The positive run is 200 amp fused on each end.
A manual engagement switch allows the second battery to be available to
start the engine or run a winch when needed. The body was bonded to the
frame with many braided, tinned 1" flat cables. This included body
sub-components and the engine and exhaust system. The coil-over-plug
ignition coils were flame-sprayed with a 95/5 Al/Zn at an aerospace
flame-spray house in San Diego. Type 31 ferrite suppressors were placed
on critical electrical systems such as the air bag, active restraint,
fuel injectors, throttle body servo and computer systems.
I selected a Hi-Q 5-160RT antenna for 160-10 meters use. I built and
potted a remote-controlled vacuum latching relay (Kilovac K43R) to
select from two different output taps of a W2FMI UNUN (18 and 32 ohms).
I built an antenna mount for the Hi-Q antenna which is made of two
layers of 1/2"x2" 304 SS mounted into the rear transfer bar for the
heavy duty trailer hitch assembly. There is a turnbuckle between the
frame and the antenna mount to support the cantilever beam design and
dampen vibration. The Hi-Q antenna has a lengthened lower mast section
and fiberglass struts to provide support for lateral thrust. The
antenna uses a Hi-Q quick disconnect mount and military-grade electrical
quick disconnects for the motor and selsen lines inside the antenna.
There is also a six inch air-core choke wrapped with about 30 turns of
RG-213 feedline. N-connectors were used for all exterior unions to
provide better weather resistance. The control line from the antenna is
suppressed with more type 31 ferrite chokes internally and external to
the antenna.
The antenna is fed about 600 watts from a Metron MA1000b SS amplifier.
VSWR is monitored at the amplifier output with a Comet remote sensing
meter. The amp is excited with an early vintage Icom 7000 with two
external small muffin fans mounted on the radio body top to keep the
class A driver stage cool. Radio control head is mounted immediately
behind the stick shift. Inside the center arm rest, controls are
located for transformer impedance tap selection, the antenna contactor
position (a modified Ameritron SDR 100) and the Metron amp. It is
relatively quick to change bands and tune manually.
I use a two foot extension above the antenna's five inch coil to a large
two-dimensional top hat with a three foot whip above the hat for the 160
meter band. Overall antenna length is about 11 1/2' long. The system
matches perfectly on all bands 160 to 15 meters, with a slight bump on
ten meters with the Hi-Q. The 18 ohm impedance tap from the W2FMI
factory potted transformer (CWS Bytemark Corp.) is only needed for
operation on 160 meters.
Many times people have had trouble believing my 160 meter signal was
mobile (when propagation on the band is good). Having 600 watts
available for this band is a BIG help. The tuning is critical and only
about 3 kHz wide at resonance for 160 meters mobile with the five inch
coil Hi-Q antenna. The VSWR ratio is quite stable when in motion with
this set-up, as long as you don't transmit under overpasses or next to
other large metal structures. The system has been in operation now for
about four years now without any mishaps. It is relatively quiet RFI
wise while in motion (S3 noisefloor typical) and the 7000's noise
blanker and noise reduction circuitry is most helpful as well.
I hope this description is of some use to the mobile community on top band.
73
Paul WN7T
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160 meters is a serious band, it should be treated with respect. - TF4M
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