The KY-8 was one the of the NESTOR family of crypto devices strictly for vehicle mounting.  They were bulky, quite heavy and mostly unreliable, but in it's heyday, it was about the only portable SECVOX (secure voice) system available to the military for use in the field. Numerous quantities were issued to the various US forces -- Army, Air Force, Navy and Marine personnel and hauled through many a battle.

KY-8 photo courtesy NSA

Joe Martin, expands on this, "This piece of  equipment played a key role in the EC-47 missions in
Southeast Asia, of which I was a part for most of 1970-71. We (the USAFSS Morse intercept operators) passed the target call sign, location, and other relevant info to the ASA troops on the ground via KY-8 or, God forbid, by "one time" pad if the secure voice failed.  A KY-8 malfunction was not cause for abort, but nobody looked forward to having to use the pads. In 270+ missions, I recall having to do it only once.

This is the KYB-6/TSEC base unit, an assembly of TSEC/KY-8. (Photo by Ralph Simpson)

The senior radio operator (if 2 operators only) or "Airborne Mission Supervisor" (if there was a
linguist and analyst aboard) received the KY-8 keying "paddle" as part of the leather satchel of classified stuff that was picked up prior during the  USAFSS pre-flight brief. This device was, as I recall, somewhat wider than a  man's hand, about an inch thick, and maybe 6 or 8 inches in the other dimension. It had some 30-odd (again as I recall) adjustable length serrated flat bar "fingers", maybe .25 X .125 in the cross section and protected by a [spring loaded, sliding?] "hood", that were set to the prescribed positions  for that day's encryption. The paddle fingers were inserted into a mating receptacle in the KY-8 and if all went well, we were ready for scrambled voice communication. The system took a bit of getting used to, mainly due to  the delay between microphone keying and the system 'kicking in". One also  had to be careful not to key the mic until a second or two after the other guy went silent, lest the signals somehow "clash", resulting in a "beep and  a rush" (as we called it) rather than the intended transmission.

After the Cambodian "incursion" in 1970, we also used the KY-8 to transmit target transmitter locations  to "Rustic" FAC aircraft which, on a lucky  day, would provide "real time" feedback for us - -no doubt one of the VERY few  examples of that in the entire history of SIGINT".

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Mike Harris was was former Marine who trained at the Marine Basic Electronic School at MCRD San Diego. He recalls some of his experiences with the KY-8.

"Because the Marine Corps did not have a school for crypto training, we were sent to Fort Monmouth NJ, an Army base. The classrooms locked like blockhouses Windows were fitted with bars and loud music was played on the outside. We took no material in or out. When our day was finished, we left everything on our desks.

We were all promoted to E-4 (NCO s) before we were sent to our assigned posts.  This was done to keep us from pulling mess and other kind of duties and allowed us to focus on the class work.

One of the fun and challenging courses involved tracing a logic signal through a circuit of logic gates. The course would give you several inputs on the left side of the schematic and the task was to move those signals through the system and determine the signals on the output.

I was eventually stationed with 2/5 combat battalion at An Hoa which was about 25 miles south of DaNang.

Each morning I would pull the clam shell unit from the box and set the code. The most common repair needed was to repair the control cable which the operators would tug on it to move the machine. To do this, the person I replaced left me a hand written drawing showing me which wire went to each connection inside the connector shell. It was a very tight fit and required good eyes and a steady hand with a soldering iron. I always kept a spare cable to be able to swap out if there was a failure. This unit was kept inside the battalion commanders bunker. At this time the battalion commander was Lt. Colonel Ernie Cheatham.

The other most common problem was keeping the KY-8 box cool, The solution was to leave ice on the top of the box."
 
 

KY-8 manual photo courtesy E-bay

Installing the KY-8 as an interim shipboard VHF/UHF  secure voice system.

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References and Credits:

1) Joe Martin A292X1(at)hotmail.com
6981st Scty Gp, 1967-69
6994th Scty Sqn, 1970-71
2) Ralph Simpson <ralphenator(at)gmail.com>
3) Nick England <navy.radio(at)gmail.com>
4) Mike Harris

June 1/22

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