10
Meter Beacon Page
(Under
construction)
The KA9SZX beacon is
located in Champaign, Illinois. It
operates at a power level of one-watt on 28.215 Mhz. The beacon came about from helium balloon flights that were flown
in the Midwest using 100mw beacons wrapped in insulated bags and sent up to
100,000 feet on tether of helium balloons.
These transmitters were mostly backup transmitters to allow trackers to
find the balloon in the event that other transmitters on board would fail. During one balloon flight the 100mw
transmitter was heard in Pennsylvania and California while it was lying in a
creek bed in western Indiana.
This got me thinking
if 100mw could be heard why not try something a little more permanent. I thought that one-watt would be a good
benchmark for such a beacon. My
experience being limited in what kind of transmitter could be used I
constructed a transmitter that had flown on a previous flight. But after assembly I had a severe oscillator
loading issues (would shift frequency as it was being keyed) that after several
attempts to correct it I threw in the towel and went with a small transmitter I
had seen in 73 Amateur Radio Today called a Wave Bender by it’s author Charles
Rakes, KI5AZ. It used a 7400 IC and two
2N3904 NPN transistors. It was built
dead bug style on a piece of copper and worked with about 250mw of power
out. The ID’er came about from
conversations with Steve Look, KA9SZW.
Steve thought it would be great to make an ID’er that could be placed in
a small package such as a balloon or the nose cone of a rocket and not have it
draw very much power. What he came up
with was a small ID’er that only draws 3ma and can store a huge beacon message
in a 8 pin Xilex IC. You can order one
pre-programmed from Steve’s company Monticello Micro
The antenna for the
beacon was a Cushcraft CX-1000, a 5/8 wave CB antenna retuned for 28.215 Mhz
mounted on a 10 foot pole in the back yard.
The KA9SZX/B came on
the air on January 19, 1992 and has mostly been on the air since then. It has gone thru several changes over the
years. I had only planned to keep the
Wave Bender running long enough to get another transmitter but comments and
QSL’s from it were pretty amazing so we kept the transmitter on line for over 4
years finally replacing it in July 1996 with a CB/Car alarm transmitter. This transmitter spent it’s early life in a
TV live van. During a rewire of the
truck it was pulled out and was going to be tossed in the trash. I saved it and brought it home.
The Wave Bender had
been a good transmitter but I wanted to make some changes. I wanted the one-watt of power that had been
my original intention. I also wanted to
get away from keying the crystal itself for improved frequency stability. I modified the car alarm transmitter so
that the oscillator had it’s own supply and the driver and final were to be
keyed. The modulator IC and transformer
were removed and a adjustment cap was added to the oscillator circuit to
fine-tune the frequency. This
transmitter was placed in a used rack mount box and a power supply was built
into the box for the beacon and ID’er.
Power can be set on this transmitter and has run at the five-watt level
on certain occasions. At one watt
nothing gets warm in the transmitter or power supply and at five watts only the
final heat sink gets warm but never hot.
My only maintenance
is to check the crystal every three months for drift and to check power
output.
I will be adding
pictures to this site in the next few weeks so you can see what the beacon
looks like and will also be adding a QSL section. In the mean time if you do hear the beacon you can e-mail me at:
Mark Garrett, KA9SZX