Click for homepage
Speech encryption device - wanted item

TSEC/KY-38 was a half-duplex manpack voice encryption device, developed by the United States National Security Agency (NSA) around 1964. The device is part of the NESTOR family of speech encryption devices and was heavily used during the Vietnam War. It is compatible with the KY-8 vehicular unit and the KY-28 aircraft unit. The KY-38 was succeeded in 1975 by the KY-57 [3].

The image on the right shows a US soldier with an PRC-77 manpack radio on his back, during the Vietnam War in October 1969. Below the radio set is the KY-38 voice encryption unit, which is about the same size as the radio itself. The handset is connected to the KY-38. The total weight of the kit must have been gigantic.

This photograph was obtained via Wikipedia, where it is attributed to the NSA [4]. Note how­ever, that the image as supplied by the NSA is mirrored horizontally and that the one shown on the right has been corrected. The image is part of this larger photograph made in Vietnam in October 1969 by SP4 Timothy F. Fease [2].

 Larger image

US soldier in Vietnam operating a PRC-77 radio with KY-38 voice encryptor. 16 October 1969 [2].

The KY-38 was introduced in 1964, together with the other members of the NESTOR family, the KY-8 and the KY-38. They were first used in the Vietnam War from 1965 onwards and were only available in small numbers. In total, approx. 30,000 NESTOR devices were produced, before they were replaced by VINSON family members like the KY-57 from 1975 onwards. The last NESTOR units were decomissioned in the early 1980s.

PRC-77 radio
The AN/PRC-77 radio was in fact a PRC-25 that had been given a solid state RF power amplifier, and was modified for the connection of digital voice encryption equipment, by adding a so-called X-MODE to the circuitry.

When in X-Mode, the filters in the audio path of transmitter and receiver are bypassed so that the full bandwidth of the set can be used.

 More about the PRC-77

PRC-77 military radio

Compatible devices
  • Vehicular Unit
  • KY-28
    Aircraft Unit
  • KY-38
    Manpack Unit
  1. Brooke Clarke, AN/KY-38 Secure Voice System
    Retrieved November 2016.

  2. SP4 Timothy F. Fease, Image of soldier with AN/PRC-77 and TSEC/KY-38
    16 October 1969. 53 Sig Bn. 3791-30/AGA69. 1

  3. Wikipedia, NESTOR (encryption)
    Retrieved November 2016.

  4. Wikipedia, AN/PRC-77 Portable Transceiver
    Retrieved September 2019.
  1. Declassified by USAPA, 30 January 1970.

Further information
Any links shown in red are currently unavailable. If you like the information on this website, why not make a donation?
Crypto Museum. Created: Saturday 01 October 2016. Last changed: Thursday, 19 September 2019 - 09:10 CET.
Click for homepage