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Author Topic: Mystery Antenna  (Read 692 times)

Curt Sorensen

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Mystery Antenna
« on: January 29, 2021, 04:36:27 pm »

Hi,

I'm looking at blueprints from 1969 that shows five TV studio and two theater floor plans. The largest studio is 100'x60'. All seven spaces have  each a "100 KC Loop Antenna" that travels around the rooms about eight feet off the walls. There is nothing visible, so presumably they are either buried in the concrete floors, or were never installed. I can't find anything Google-wise that gives me a clue. So curiosity makes me ask, what could they be for?

Thanks for playing,
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Curt Sorensen
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Mac Kerr

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Re: Mystery Antenna
« Reply #1 on: January 29, 2021, 05:00:44 pm »

Hi,

I'm looking at blueprints from 1969 that shows five TV studio and two theater floor plans. The largest studio is 100'x60'. All seven spaces have  each a "100 KC Loop Antenna" that travels around the rooms about eight feet off the walls. There is nothing visible, so presumably they are either buried in the concrete floors, or were never installed. I can't find anything Google-wise that gives me a clue. So curiosity makes me ask, what could they be for?

Thanks for playing,

They are wire loops used as antennas for a hearing assist system. They are commonly laid under carpet.

Mac
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Curt Sorensen

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Re: Mystery Antenna
« Reply #2 on: January 29, 2021, 05:54:13 pm »

Hi,

That surprises me as it was 1969. Also, I see the use in a theater, but less likely in a TV studio. Wireless IFB perhaps, but again, in 1969?  I don't mean to doubt you, I just thought things weren't very advanced then, I know I wasn't.

Thanks,
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Curt Sorensen
Madison, Wisconsin

Brian Jojade

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Re: Mystery Antenna
« Reply #3 on: January 29, 2021, 07:41:20 pm »

Hi,

That surprises me as it was 1969. Also, I see the use in a theater, but less likely in a TV studio. Wireless IFB perhaps, but again, in 1969?  I don't mean to doubt you, I just thought things weren't very advanced then, I know I wasn't.

Thanks,

Induction Loop systems were first put in place in the late 30's.  They are technologically super simple devices.  Essentially a loop of wire in the room connected to a regular amplifier that emits the audio signal which can then be picked up by anyone in the room with a simple device that could fit in a pocket with headphones attached.  Behind the ear hearing aids came into play in the 70's which meant no need for the extra box in your pocket.

Note that these are NOT radio systems. It's simple induction of the signal, making it a super simplistic system that just works.
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Brian Jojade

Philip Roberts

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Re: Mystery Antenna
« Reply #4 on: January 29, 2021, 10:57:07 pm »

Induction Loop systems were first put in place in the late 30's.  They are technologically super simple devices.  Essentially a loop of wire in the room connected to a regular amplifier that emits the audio signal which can then be picked up by anyone in the room with a simple device that could fit in a pocket with headphones attached.  Behind the ear hearing aids came into play in the 70's which meant no need for the extra box in your pocket.

Note that these are NOT radio systems. It's simple induction of the signal, making it a super simplistic system that just works.
If it's a Induction loop system why would it be labeled "100 KC" aka 100 kHz? Of course it's possible that it is standard induction loop and the drawing is simply wrong.

Philip
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Mike Caldwell

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Re: Mystery Antenna
« Reply #5 on: January 30, 2021, 11:01:56 am »

If it's a Induction loop system why would it be labeled "100 KC" aka 100 kHz? Of course it's possible that it is standard induction loop and the drawing is simply wrong.

Philip

I noticed that to, was it a low band AM system or a just a misprint.

Henry Cohen

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Re: Mystery Antenna
« Reply #6 on: January 30, 2021, 11:38:34 am »

If it's a Induction loop system why would it be labeled "100 KC" aka 100 kHz? Of course it's possible that it is standard induction loop and the drawing is simply wrong.

"KC" = kilocycles [per second]. Very common terminology in electrical engineering up through about the 1970's/1980's.
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Henry Cohen

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Henry Cohen

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Re: Mystery Antenna
« Reply #7 on: January 30, 2021, 11:44:50 am »

I noticed that to, was it a low band AM system or a just a misprint.

If an induction loop, neither AM, FM or any other electric field modulation. The current and voltage amplitude in the wire is modulated and the resulting magnetic field is detected by the receiving telecoil or other detector.
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Henry Cohen

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Russell Ault

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Re: Mystery Antenna
« Reply #8 on: January 30, 2021, 12:25:49 pm »

If it's a Induction loop system why would it be labeled "100 KC" aka 100 kHz? Of course it's possible that it is standard induction loop and the drawing is simply wrong.

I noticed that to, was it a low band AM system or a just a misprint.

I was wondering that too. Given that it's unlikely any of these loops come close to being large enough to efficiently transduce a 100 kHz RF signal, and that the only signal in that frequency range (in ITU region 2, anyway) that might have been remotely interesting is the NIST clock (at 60 kHz), and that 100kHz exactly was in use for Loran-C at the time, it seems unlike it was intended for an RF application.

My personal WAG is that it is an induction loop, and that 100 KC was written either by someone who didn't quite grasp the intended application or for someone who didn't quite grasp the intended application (i.e. "Hey, whadda we doin' buryin' this {expletive} cable in the {expletive} floor for?" "It's an induction loop." "What the {expletive} is an induction loop?!" vs. "It's a 100 kilocycle loop antenna". "Oh. For a radio. Huh. Okay.").

Or maybe it's a bandwidth spec. Even for a speech-only system you'd want at least 6 or 7 octaves of bandwidth, so what's 3 or 4 more?

WAGs are fun! :D

-Russ
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Re: Mystery Antenna
« Reply #8 on: January 30, 2021, 12:25:49 pm »


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