[ARC5] SCR-522 components

[D C _Mac_ Macdonald]

I converted the transmitter so my newly Novice licensed wife (WN6DFR) could get on 2m phone.  I probably bought a simple 2m converter to use with my HQ-145X.  I still have that transmitter in the rack cabinet in the garage.  Unfortunately, the matching RA-62 power supply was a casualty (like a hole lot of other stuff) in the infamous Oklahoma City F-4 tornado that nailed our house and neighborhood and 68 people on 3 May 1999.  I used Lafayette (IIRC) Vernier dial mechanisms to tune each of the four tunable stages.


Anybody interested in acquiring this antique?  HAR!


* * * * * * * * * * *
* 73 - Mac, K2GKK/5 *
* (Since 30 Nov 53) *
* Oklahoma City, OK *
* USAF, Ret'd 61-81 *
** FAA, Ret'd 94-10 *
* * * * * * * * * * *

________________________________
From: arc5-bounces at mailman.qth.net <arc5-bounces at mailman.qth.net> on behalf of Mike Everette via ARC5 <arc5 at mailman.qth.net>
Sent: Tuesday, August 8, 2017 14:35
To: Cliff Miller; ARC5 at mailman.qth.net
Subject: Re: [ARC5] SCR-522 components

Believe it or not, the receivers were much easier to convert than the transmitters.  QST and CQ published articles on doing this during the late 40s and early 50s.  It was not that difficult to make them tunable and bandspread the tuning to cover the 2 meter band.  Notice, I didn't say it was quick and dirty; this did require some disassembly of the equipment and of the receiver front end to avoid breaking the ceramic shafts in the tuning capacitors when removing plates to accomplish the bandspreading.

My 522 receiver, so converted, had a squelch-opening sensitivity of about one microvolt on AM.  I later grafted an FM bandpass filter, second IF and detector from a Motorola packset receiver into it, using the first 2 stages of the 12 mc IF in the 522 as intended and rewiring the third one into a crystal-controlled converter using a 12SA7 to take that IF down to 455 kc. The result had amazing sensitivity, less than 0.3 uV if I remember right, but was very susceptible to drift from air currents in the room.

Putting the receiver section into a case from a BC-375 tuning unit helped somewhat.

I learned a lot from the 522.

73

Mike

WA4DLF

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