E-648
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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.
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". 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 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:
further literature: © Martin Bösch 21.4.2012
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