|
|
|
|
|
|
|
CIA NRP EC
Covert listening device with DSBSC audio masking
- this page is a stub
SRT-57 is a covert listening device (bug),
developed around 1967
by the Dutch Radar Laboratory (NRP) for the
US Central Intelligence Agency (CIA),
as part of a long-term research contract under the codename
Easy Chair.
The device works at a spot frequency in the 230-250 MHz band and
features audio-masking by means of
double-sideband suppressed-carrier (DSBSC) modulation. It has
a built-in switch receiver that operates in the same RF band,
with separate on/off signals.
|
The device was developed during the course of 1967 and was presented
as an evaluation kit to the CIA in October 1967. It consists of an RF unit
(transmitter) with built-in switch receiver, an audio modulator with
subcarrier modulation of which the 20 kHz subcarrier is suppressed (DSBSC),
and an external demodulator for this signal type was supplied that could
be retrofitted to an existing SRR-40 surveillance receiver.
The image on the right shows the complete kit as it was provided to the CIA.
At the right is a spare 20 kHz crystal, for subcarrier re-insertion .
|
|
|
The the switch receiver allows the bug to be remote controlled
and is 'borrowed' from the earlier
Pied Piper research project,
that resulted in the evaluation version of the
SRT-40 target element (bug)
and SRR-40 listening post receiver.
A complete SRT-57 evaluation kit consists of the following:
|
- SRT-57 RF unit with switch unit
- SRT-57 modulator with 20 kHz DSBSC
- Patch cable for testing above modules
- Demodulator for existing SRR-40 receiver
- Spare 20 kHz crystal (for subcarrier insertion)
- Operating manual
|
Supply +3.7 V DC Current 95-100 µA Subcarrier 20 lHz Input 500 µV RMS at 4000Ω Output 230 mW p-p, or 56 mV RMS into 25kΩ Response 300-5000 Hz ±3dB Suppression > 30dB Compression yes
|
Supply +4.05V (on) Switched +3.7V (on), +0.15V (off) Current 1.96 mA (on), 24µA (off) Frequency 230-250 MHz Output ≥ 1 mW (on) Impedance 50 Ω Pulling 0.3 MHz p-p (VSWR = 2) Sensitivity 0.27 kHz per mV Index 0.75
|
- Manual for SRT-57 evaluation equipment
NRP, October 1967.
|
|
|
|
Any links shown in red are currently unavailable.
If you like the information on this website, why not make a donation?
© Crypto Museum. Created: Sunday 27 November 2022. Last changed: Tuesday, 13 December 2022 - 09:26 CET.
|
 |
|
|
|
