Astro Communications Lab. / ACL SR-209
Astro Communications Lab., Gaithersburg, Maryland

Swiss Army Communication Sets
Synoptic Table
Army Receiving Sets
Exxx Designations
E-600 / Autophon E39
E-601 / Zellweger E41
E-602 / Autophon E44
E-603 / Autophon E45
E-604 / Autophon E46
E-606 / Velectra
E-627 / Autophon
E-628 / Autophon
E-629 / Collins 51J-4
E-645 / Siemens E311
E-646 / Zellweger
E-648 / ACL SR-209
E-649 / Watkins-J.
E-653 / Telefunken E863
E-655 / Racal RA1217
E-656 / Racal RA1772
E-657 / Telefunken E1501
E-658 / R&S EK070
E-659 / Watkins-J. WJ-8888
E-660 / Teletron TE704C
Equipment List
Army Manuals
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about / contact

überarbeitet am 21.4.2012

In the sixties, the Swiss Army acquired a few samples of the VHF / UHF surveillance receiver SR-209 made by the American company Astro Communications Laboratory, Inc., Gaithersburg.
The receiver got the Swiss Army designation E-648 and has been in use mainly for military air traffic control, it was replaced by the E-649.
ACL SR-209

Analog frequency dial,

AM (A3), CW (A1), FM (F3)

30 - 100 MHz (VHF), 0,5-1 / 1-2 GHz (UHF)

Selectivity -6 dB
20 / 100 kHz, 3 MHz


RF Gain, panoramic spectrum display

In contrast to most sets found as international surplus, the Swiss Army variant has been built into a 19" rack desktop cabinet with double units height, so the cabinet has not only room for one but for three "tuning heads".
The receiver has a modular construction, beside the basic receiver unit, there are a panoramic display unit and the tuning heads, tuning units with their individual tuning knobs and dial, even with individual I.F. strips which will make the set extreme versatile with different I.F. bandwiths from 10 kHz - 8 MHz.

On the main unit, you switch on the receiving system and select the respective tuning head, the receiver can demodulate transmissions in CW (the BFO is active in CW mode and with I.F. bandwidths below 250 kHz), AM, FM and PAM (pulse modulation). Next to the instruments for signal strength and FM signal center, you find the control for the RF Gain, the AF and Video signal gain and a headphones jack.
In the ACL Signal Display Unit, a small cathode ray tube will act as panoramic monitor to display the signal levels in a band segment, you can control the display signal level and the width of the band segment displayed. Even very short transmissions will appear as peaks in the display, the operator can tune the receivers center frequency to the signal peaks to identify the content of unknown transmissions.

In my set, which has seen use with the Swiss Army, there are tuning heads SH-201P to cover the military VHF band and the UHF/SHF tuning heads SH-204P and SH-205P to cover the 0,5 - 2 GHz range.

When you have a look to the block diagram, you will find that the signal coming from the tuning had will be fed to one of the intermediate frequency strips, which are different corresponding to the I.F. bandwidth: I.F. module A3 (I.F. bandwidth > 250 kHz), A4 (50 - 250 kHz) or A5 (I.F. bandwidth below 50 kHz); after the detector module A6 it will reach the AF amplifier A8 gelangt; the CDR / Squelch amplifier A9 will control the squelch / muting level and the video amplifier in module A7 feeds the panoramic monitor unit.

The following tuning heads have been available from the manufacturer:

  • SH-201P: 30 - 100 MHz
  • SH-202P: 90 - 300 MHz
  • SH-203P: 250 - 500 MHz
  • SH-204P: 490 - 1000 MHz
  • SH-205P: 990 - 2000 MHz

further literature:
d/e: ACL SR-209 at www.radiomuseum.org

© Martin Bösch 21.4.2012