[GreenKeys] Polar Relays- A question and a tale

[Henning Treumann]

Especially Russia did use extensively double current (polar relay) RTTY
systems. Every Russian terminal unit has got a double current output for
teleprinters or land lines.

Germany (East and West) usually used single current systems
Only for long distance subscriber lines, double current , hence systems
with polar relays were used.
But a polar relay is used in every TW39 Telex control (dialling unit) to
detect the reverse of polarity at a call in Europe.

Henning  DF3OE
i-Telex 925302, 92612 ...
www.i-telex.net



Bruce Gentry via GreenKeys <greenkeys at mailman.qth.net> schrieb am Di., 6.
Apr. 2021, 20:23:

> 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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