KG6DI Athens OH Marathon
Glen Ebon APRS Digipeater
(Click individual images to enlarge to Hi-Res)
On location at Glen Ebon crossing. Telescoping mast extended 25 ft.
The antenna is a Diamond X-50 omni. that provides moderate gain
at both 2-meters and 70 centimeters. The antenna is installed
while the mast sections are collapsed but fastened to the base.
Then the sections are pushed up one at a time and the
hose clamp tightened. Each tube is marked with permanent ink
one foot from the bottom to indicate the maximum extension.
Ignoring this mark would make for a most memorable
public service event. This antenna system has performed well at
winds around 7mph with the mast extended to a height of 25'.
Three more feet can be gained by moving the pvc conduit up in
the angle iron. Higher winds call for less extension of the
tubes.
The base for the mast is 20" X 20" X 1/2" plate steel.
Welded to it is a 4'-6" length of 2" angle iron (steel) 3/8" thick.
The assembly weighs over 80 lbs. so dropping it on your
foot would also make for a memorable public service event.
The base is placed on a firm surface made level with lime stone
then driven upon with one of the truck tires to provide ballast.
The mast is made of 6063-T832 aluminum tubes 6' in length, 0.058
wall thickness. There are five concentric tubes in sizes 1",
1.125, 1.25, 1.375, and 1.5 and these are made to slide one
inside the other. DX Engineering supplies these with one end
split for use with a stainless steel hose clamp. The 1.5" tube
is inserted into a 4' length of PVC conduit. The conduit is
split at the top and bottom to hold the aluminum tube with hose
clamps. The conduit distributes the clamping force of the
muffler clamps that are used to fasten the mast assembly to the
base assembly.
The radios are mounted in an ammo box for easy transport, one
for voice and one for APRS. Also in the box is the TNC and GPS.
We built many of these
systems to track runner vehicle and support vehicles for the
Baker to Vegas Challenge Cup Relay in the California and Nevada
desert. For the Athens Marathon, it was used only as a voice
radio and digipeater.
All power and RF connections are made through bulkhead
connectors in the wall of the box.
A feature of prime importance is bringing
the TNC's serial port out to the front panel.
Copyright © 2010 - Robin J. Kinney KG6DI
