[ARC5] "Heath" AircraftTransmitter 0 Update

[Robert Nickels]

Here's a quick update on my "high power" Heath HT-4 transmitter.

Like Daves HT-4B3, it basically worked-as is.   The tight space and wire 
harness made it a little difficult to noodle out the fact that the B- is 
separate and switched to ground via the T/R relay, but it came right up 
on 3885 with tweaking of the tuning cap,  and is putting out the rated 6 
watts into a 50 ohm load.    (Took another little while to realize that 
someone had reversed the wiring or rotated the antenna switch, as the 
"Fixed" and "Trailing" antenna outputs are reversed).   Modulation is 
full and communications quality with a Shure carbon mic.  Total current 
from the 250 volt supply is 90 ma dead carrier, peaking to 130 or so on 
voice peaks.

It's going to be fun to put this baby on the air!   It's designed to run 
on 6 volts DC - the filaments obviously don't care, but the relay buzzes 
when operated on AC.  I think an old 5 volt regulated power supply can 
be cranked up do the job.   The open area on Daves chassis is where the 
T/R relay mounts, but it and the additional filter cap were eliminated 
on the battery version.  Neat that it provides antenna switching for the 
receiver too.   Also, mine has a slide switch assembly that changes from 
6 to 12 volt operation.  A reversible metal plate locks the switch in 
place so it can't be inadvertently changed.

If you read the link that was posted, you discovered as I did that 
these  transmitters were designed for Heath President Howard Anthony by 
friends who worked for Southwest Airmotive,  and were built in the 
fledgling Heath plant on Territorial Rd. in Benton Harbor.   I think we 
have two examples that prove they both did a great job!

73, Bob W9RAN