[GreenKeys] Polar Relays- A question and a tale

[Bruce Gentry]

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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