KFF Homebrew Tips

 

 
 
 
KFF's Trailer Tower
 
This is just an introduction to my trailer tower project. As time and weather allow,
more and better pictures will be posted as well as details of the various antennas
and control systems.
 
Basically this thing was purchased as a used, stripped down light tower, much as
you see today at emergency sites or construction jobs. A 30 foot tower was still there,
and the cabinet that originally hold the big lights and reflectors, not much else.
 
Over about a two year time period, this was my main hobby, bringing it back to life
and modifying it for ham use:
 
 
 
Hand winches were added to raise the tower to vertical, brackets welded on to hold it there
when erect, racks attached for the big 6" PVC tubes that hold all the antennas, outrigger arms
constructed and brackets made to hold them in place.
Two of the  four outriggers can be seen in the picture above. The other two are on the other side.
When deployed, they fit into sockets at each corner of the bottom of the trailer chassis. Sticking
out at right angles, they provide a firm footing some 16 feet across at the four corners. Each of
the angled feet slide up and down in a socket at the end of the arms, allowing for leveling on
uneven terrain. The trailer came with locking wheels which is a real plus, once parked a lever is
pulled, locking the brakes on both wheels.
Inside the equipment bay is stored a complete set of US Army guys and anchors.
 
On the back shelf we permanently mounted a Coleman 4 kW genset, which we modified for
remote electric start. This is only needed for charging the batteries, and power amplifier for EME generally, although the local ham club likes to use the rig to power Field Day.
 
Not shown on the other side of the trailer are several 6" PVC pipes, these contain the
antennas as follows:
 
160/80/40M is a Butternut HF-2 vertical with LJE radial plate, designed as a raised radial
antenna. This means the radials are at 10 feet in height. If MF ops are desired while the tower
is being used for other bands, we have a home made drive-on wheel mount for ground mounting.
 
20-15-10 is a Mosley TA-33 jr, all of which fits in a single tube for transport.
 
Another tube holds a Cushcraft R5 for WARC and general purpose use.
 
6M is well represented by a home made Yagi, designed to be either 3, 4 or 5 elements
depending on the need. All the elements are marked for quick assembly and provided with
wingnuts to make it go fast. Each iteration is spaced optimally for the boom length in use.
I also have a really light duty 3 element 6M Yagi that mounts on the van, It can be assemble
and deploys in one minute, including the rotor. The mounts fit in the trailer hitch, while a
bearing for stability is supported by the luggage rack at roof height. This setup is also used
for mountain top Meteor Scatter on 2M with a 17 element Yagi.
 
 
 
2M- four 13 element Yagis. These can be deployed in several configurations for
Meteor Scatter, Terrestrial and EME.
The latter makes use of a home made H frame, power dividers by K0RL and phasing lines by
K5GW.  I designed and built the mast mounted preamp/switching system which is in a
waterproof NEMA box.
 
222 MHz- home made Yagi built in the Cushcraft style, with all home made brackets.
 
432- ditto 222.
 
Both 222 and 432 and one of the 2M Yagis can go horizontal or vertical polarization.
 
no 903 yet
 
1296 is a pair of long boom M2's. Can't improve upon that.
 
Various of my copper loops for VHF and other typical "mobile" antennas have places
to mount on several brackets spaced all around the trailer itself. Most of these are used
while on the road, plus coordination at the site.
 
Main rotor is a Bell housing type, with quick disconnect connectors on the rotor and
control box. The wire is 100 feet long to cover all types of operations, such as a
tent, motel room.
 
EME rotor is a Pelco pan-and-tilt motor, used for TV cameras, often called  a gun-mount.
Very heavy duty with Bodine motors and Boston gears. It has been modified with a
potentiometer on both the AZ and EL shafts to feedback positioning to the control box.
Quick disconnect connectors and 100 foot cable here too. The control box is home made,
with digital readout of AZ and EL, all controlled by a joystick. This motor can also be used
in the"autoscan mode" in which it goes back and forth all by itself, as in VHF contesting,
snooping for signals.
All the rotors have a pipe mounted to the bottom which fits into a socket at the top of
the tower, being clamped in with a wingnut arrangement. No tools are required to
set up the tower. Rotors are powered by 12V inverters providing enough 110 VAC for them
and a few small accessories.
 
Electric power:
 
Battery power from heavy duty batteries was planed and tried.  Our main goal was to have
13.8V available from the batteries even when the generator was not running. Various schemes
were tried, but all of the 2V cells tried leaked when subjected to rough trails. Right now,
one or more ordinary marine deep discharge batteries do the job, OK but not great.
 
Radios:
Since my main interest is VHF+, the radios carried are heavy into that area of the spectrum.
IC-736R's with different modules give good coverage and redundancy of 6, 2, 222, 432 and
1296. Most of the VHF/UHF power amps are TE solid state. EME amp is a homebrew 8877
but the generator can only muster it to about 800W.
HF radios are whatever we decide to bring, usually a small mobile rig like a 706 or FT100.
 

Happy Homebrewing, Geo>KFF