[GreenKeys] Polar Relays- A question and a tale

[dave.g4ugm at gmail.com]

Bruce,

I don’t know about Russian equipment, but in the UK double current operation
was normal, but 80volt 60ma rather than 60volt,.

Dave

G4UGM 

 

From: greenkeys-bounces at mailman.qth.net <greenkeys-bounces at mailman.qth.net>
On Behalf Of Bruce Gentry via GreenKeys
Sent: 06 April 2021 19:23
To: greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] Polar Relays- A question and a tale

 

Did Soviet or DDR teleprinters have bistable selector magnets? I have and am
restoring a Russian/ East German R-155 receiver , which has a built in RTTY
demod. One of the several connection configurations gives a 60 volt signal
that reverses polarity for mark and space.� The tale is as follows: Over
fifty years ago when I was in high school, we were in a newly constructerd
and most up to date equipped building which included TV studios and other
audio visual gear. There was a full time studio engineer there who was
friends with a local broadcast engineer. They managed to get a metallic pair
telephone line from the radio station to the school, obstinsibly for remote
broadcasts. They devised a way to send the Associated Press signals from the
station to the school where we printed them on a model 15. The line carried
the station's audio which we listened to in the TV studio shop. A polar
relay was used in the demod at the school, most likely amplifying a low
level signal sent down the phantom on the audio line. The two engineers
refused to tell me how they were doing it. The school studio engineer was
very involved with RTTY at the time. There were lively debates in those days
about whether the� popular W2PAT demod was best with a polar relay or the
later 6Y6 keying tube.

���� Bruce Gentry, KA2IVY

On 4/6/21 12:56, Jim Haynes wrote:


It's good to see all this interest in historical artifacts like polar 
relays.� However they were not all that popular for RTTY. 

Some early demodulators, and this goes all the way back to the 1920s 
(U.S. Patent 1,705,211).� The mark frequency detector went to one 
winding of the polar relay and the space detector went to the other. 
So the decision of whether the signal was mark or space was made right 
in the relay itself.� In amateur use the W2PAT converter was published 
in January 1953 QST, page 44.� And the W2JAV converter was similar. 

Later on polar relays fell into disfavor because they added a mechanical 
element that required adjustment.� I remember a cover of RTTY magazine, 
May 1963 issue with a cartoon coat-of-arms "Knights of the Mark Three" 
showing a polar relay being assaulted with an axe.� Mark Three was a 
converter designed by the great RTTYer W6NRM.� Driving the selector magnet

directly from a tube, and later from a transistor, became the norm. 
The mark/space decision was made elsewhere in the demodulator.� Polar 
relays also disappeared from commercial and military designs. 

Polar relays built into the machine were always optional, needed if 
the machine had to receive polar signals or operate on low line currents. 
These are all conditions connected with wire-line circuits, not radio 
or local loops. 

����--- 

����"Ya can argue all ya wanna, but it's dif'rent than it was." 
����"No it ain't! No it ain't!� But ya gotta know the territory." 
������� Meredith Willson, The Music Man 
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