[TMC] SBT-1KV lives!

[Duncan M. Brown]

We got the AWA Museum's SBT-1KV put back together and fired up today.  Got
800 watts out on 75 M into dummy load. (Didn't try higher power because the
screen current meter was about to peg. Need to play with it a little more.)


We were about to put it on the air, but there is something funny with the
antenna relay; it is not passing ANT signal to RX.  (TX OK, passing 800W).
With TX unkeyed, took ANT coax off dummy load and tried to measure
continuity to RX BNC on bottom of AX-198: no continuity, but ANT coax reads
short to chassis!! ??  Schematic doesn't show any shorting contacts on
Antenna relay.  Won't be able to tear into it until I return to the Museum
next Tuesday.  Any ideas??

How do you key your TMC transmitters for PTT service?  We started out
following the PAL-1K manual's tuning procedure (Table 3-2): Turned on the
"Transmitter Voltages" switch and then the "Final Voltages" switch; checked
the voltages and idle current and then keyed the SBE exciter with the
microphone plugged into the SBE; dipped & loaded and got POWER OUT.  But
when we wanted to put it on the air, realized that the mic was just
controlling the exciter and not the whole TX.  Am I missing a jumper
somewhere that allows the mic to also key the TX voltages?

Also seems to be something funny with the ALDC contol on the RFD-1.  The
PAL-1K proceedure (Table 3-2) says to start with it set fully CCW; then
when all tuned up, to advance the ALDC control CW until drive is cut back.
But when I advance the ALDC control CW, output power goes UP!?? (carrier,
no modulation).  Got same results using INT or EXT ALDC.  Is this normal??
Manual is not very clear on ALDC setup; How do you set it up?

Feb 21-22 is the AWA AM  QSO Party
(http://www.antiquewireless.org/otb/amateur0109.htm  - scroll down). We
plan to be operating the SBT-1KV & GPR-92 on 20M with the call W2AN.  So
fire up thoes old rigs & make some AM noise!

Thanks & have fun, 

Duncan Brown, K2OEQ

AWA Electronic Communication Museum
http://www.antiquewireless.org/