[MRCA] Identify Strange Item

[Ray Fantini]

Speculation, it’s a receiver that would have been used to decode subcarriers on microwave and satellite transmissions. In the old days before everything went to digital common carrier microwave and a lot of the old C Band satellite traffic carried subcarriers although most I remember were at higher frequencies, it was common to use both USB/LSB and have a different conversation on each sideband.
The weird thing was I always thought WJ had a lock on that business being there were tons of there stuff for decoding subcarriers, don’t know why but think most common carrier microwave used USB/LSB where the Satellite stuff was FM.
There are a lot of the selective voltmeters that are floating around on the surplus market that were used for setting the injection level of subcarriers on microwave channels back in the common carrier days but all the common carrier technology is long gone today.


Ray F/KA3EKH

From: mrca-bounces at mailman.qth.net <mrca-bounces at mailman.qth.net> On Behalf Of Doran Platt
Sent: Tuesday, March 16, 2021 3:34 PM
To: mrca at mailman.qth.net
Subject: [MRCA] Identify Strange Item

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My friend brought over a piece of gear that I cannot identify, nor fathom its actual end use.  He picked this, and an Eico novice tx at a junk store. Its is nomenclatured as "Transistorized Channel Selector" and apparently mfg by NSA's lab.  AC powered, 8 1/2" high rack mount assy.  It has a 5 band, slide-rule dial assembly not unlike an Eddystone or National (but not). The 5 bands go from 0-100 kHz.  It has a BFO selector USB, LSB, and AM, input and output gain conbtrols and a.c. power switch.  No other controls.  There is a nice schematic inside that tells it all... if one knew what it was really used for.  It has a single LPF input via 1/4" phone jacks. There is a 5 band LO going to a balanced mixer, thence to a Collins 455 mech filter.  Signal then goes thru a 455 kHz strip, a diode detector and crystal controlled BFO for USB and LSB.  Again, no front-end gain, no AVC, or pre-selection.  Input sensitivity to get a usable signal in the headphones is above perhaps .1v Anyone have any idea?  Maybe a back end for a VLF receiver system?
Jeep K3HVG
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