[Collins] Collins military S line

[Dr. Gerald N. Johnson]

I believe S-line and KWM-2 were used at US Embasies also.

The MARS station at Ft. Belvoir had two shifts of regular army troops 
running phone patches from Nam. They weren't hams. When I was there I 
used the station on 80 emters to work my dad once a week and I also took 
care of the station radios. The newest station had a KWM-2A and Kenry 
@K-3 linear which the seargent in charge (a ham) didn't know how to tune 
properly so it was only putting out a couple hundred watts. He had tuned 
for plate and grid currents but not for maximum output. Another station 
had a Viking 500 and then the S-line and that's were I found a useful 
mod to the screen supply of the 30S-1 for better CW signals. It had the 
monitor scope and I could see the amplified envelope didn't follow the 
keying. Adding 350 mfd to the 30S-1 scree supply fixed that and gave it 
great punch. That had to be done to the 208U-10 a few years earlier to 
make them handle CW for a Swedish order.

One evening, that rig needed work and the band to Nam was dead so I was 
able to use the new rig on 80 meter CW and when I finished tuning I had 
to back it down to 1.5 KW out. After an hour of high speed CW, the phone 
patch crew wouldn't let me leave until I made a new tuning chart for the 
PA. Next week they said Nam stations said, "We see you finally got the 
final turned on." I had to fix the Henry amp once too. Set screw in a 
sprocket that coupled the input and output bandswitches worked loose. I 
had to make an extended spline wrench to reach it.

While that was a MARS activity the operators were not volunteers but 
active duty troops. Sort of mixed between military and MARS. I was not a 
MARS member at that time, but was a conscriptee on active duty. The 
latest station equipment (including a big LP that wasn't up yet) had 
been purchased with a grant of money from Saigon PX profits so it wasn't 
strictly military property. The distinctions were a little fuzzy.

The phone patch station had at least two phone lines and two operators 
so as each troop in Nam got to call home and approached the end of his 
allotted time, the second op would be placing the call and preparing the 
called party for the radio operation so little propagation time was 
wasted setting up the call, on the air switching was rapid. And if the 
called party didn't answer they went on to the next on one the daily 
list. They had the capability of several frequencies to make that 
halfway around the world path work, generally near ham bands.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.

On 7/6/2014 11:31 PM, L Ritta wrote:
>
> Hello All
>
> I have an interesting question about the Collins S line and it's use in the
> US military.
> I understand it was used for Mars, but was it used in combat for tactical
> communications.
> If not what was it's primary mission?
>
> 73's Lee
>
>