[ARC5] SCR-522: Rethinking The Old Gal

[David Stinson]

Once, I was disdainful of the SCR-522 VHF rig.  Not because of its 
history, which is quite significant, but for aesthetics, calling it an 
"ugly black lump of a radio."  And it is.

But I'm recently reminded of high school dance days- how there was 
always the "plain girl" who sat with a friend and never got asked to 
dance, so a fella would eventually feel bad that she's being left-out 
and ask her to dance.  To his surprise, once she got past her 
justifiable reticence, he finds she can "cut a rug" with the best of 
them, and surprise- she's really quite a nice and fun person.  Some 
life-long marriages have started this way.

Well, I recently took out the SCR-522 for "a dance," trying to complete 
some earlier work now that I have some better test gear available and 
half-an-hour of time every few days.  Once properly restored and 
carefully aligned, the "plain girl"  surprised me. The manual specs the 
receiver sensitivity at around 3 microVolts, 6 as "acceptable."  Given 
the 9000-series tube front-end and the state of the VHF art in 1943, 
that's about right.  Well, this lady is doing about 1.5 microVolts for a 
good usable signal.  The local UNICOM on 122.8 sounds excellent. 
Transmitter is good as well.
Rigs works peachy on the BC-1303 tester, but the Antenna relay won't 
throw when connected to the BC-602.  Still working on that issue.

https://youtu.be/NRHB9DlARXM

On crystal substitution using that DDS gizmo-  This rig requires more 
drive than the SCR-274 VHF.  Square waves at about 10V peak needed for 
the receiver.  Higher than that and the receiver stops working.  The 
transmitter requires an even harder whack- 18-20V peak, and the DDS 
connection at the transmitter crystal socket causes a ground loop with 
60 Hz gremlins.  For some reason, the transmitter will self-oscillate 
with the DDS connected and less than 12-15V drive, probably from the 60 
Hz crud.
Luckily, I have crystals close enough to etch to where I need them.

This "plain girl" has won me over.  I don't want to marry her, but a 
"dance" now and then is fun.

GL OM ES 73 DE Dave AB5S



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