THE 2
METER
1KW AM
TRANSMITTER
- The 2 meter AM 1KW transmitter,
is a restored Air traffic
control transmitter, which sports a pair of Eimac
- 4CX250B tubes in the final amplifier
stage. The front panel is 24 inches
wide and 14 inches high, and the deck is
- 27 inches deep. I got this at the
Syracuse Ham-Fest in 1986, I wondered
if it could be moved to the Amateur band,
- there was no paper-work with it, no
power supplies, just the R.F. deck.
- I took a couple of days to
"BUZZ" out the wiring in the unit and determine
what I actually had to work with. The deck
- was really clean, so tracing
circuitry wasn't all that hard. I traced input
and output circuitry and determined the
- input/output would tune from 100
Mhz to 170 Mhz (Lucky). The input circuit is a balanced type with split
stator
- cap across the input coil which is
made of # 14 silver plated wire. The
output is tuned lines across a capacitor that looks
- like it can handle the high RF volts
at 2 meters with "plate modulation".
- I bought surplus an AC/DC 250VDC
100MA which is in a small package, and
a linear not a switching power supply
- for the bias supply (adjustable). I
then built a 0 to 500 VDC supply for
the screen circuit, and a 2500 VDC adjustable
- high voltage power supply
(solid-state) for the 4CX250 screen and plate
circuits and the modulator.
- This rig is driven by the Heathkit VHF-1
which is only used as drive and frequency control exciter for the Final
Amp.
- The amp is wide so I had to fabricate
a rack mounting scheme to allow it
to be mounted in. The rack holds the AMP.
- a panel with meters for grid, screen,
and plate currents. High voltage
is monitored for plate and screen.
- The amp and all power supplies and
metering and control circuitry, fit
in a rescued 24 inch wide cabinet, which
- is big enough to hold everything, and
of course is caster mounted so I
can move it with a "sincere" push!
- The cabinet:
Front view of Rack Cabinet.
Rear view of Rack Cabinet.
