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Old 1st December 2008, 09:25 PM   #1
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Lightbulb build a STEREO weathers fm cart!

In case you don't know what an fm pick up is -
Weathers FM Cartridge


Anyways, it turns out Paul Weathers filed a patent for a stereo FM cartridge. View Patent

And here's an RF circuit for an RF Condenser Microphone which work on the same principal. RF Circuit Does the RF Circuit need to be modified for an fm cart?


Seeing as how people build custom microphones, why not a cartridge? Anyone feeling inspired?


PS Putting something like this together is over my head but building it looks pretty straightforward. Any ideas?
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Old 1st December 2008, 10:47 PM   #2
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I spent a year trying to get that to work (the Weathers mono was an astonishing cartridge) with no success. I hope someone more clever than me can succeed.

Of course, you need to make a wooden arm, too.
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Old 2nd December 2008, 12:38 AM   #3
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My all time favorite audio comment....

>For bachelors, or people with unnaturally good control over the spouse and children, the Weathers is excellent.<

There's probably a reason no one has made an attempt at repeating this. After all we now have $600,000 current out tube amps.
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Old 2nd December 2008, 01:50 AM   #4
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FYI: Figure 5 is for the more common stereo 45 degree record pressing.

The second design is for the less common "hill and dale" stereo.

It seems crosstalk was a problem with these carts? Any solutions?

SY, it would be great if you could share any valuable learning experience you gained from your attempt!
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Old 2nd December 2008, 01:50 AM   #5
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To answer my own question someone suggested FM Multiplex technology on another forum, like radio stations use. No idea how that works.

Or could you use different frequencies for the RF circuit : like tuning into different radio stations and eliminate crosstalk altogether? More questions than answers, I know.

Again, way over my head.
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Old 2nd December 2008, 01:50 AM   #6
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Quote:
My all time favorite audio comment.... >For bachelors, or people with unnaturally good control over the spouse and children, the Weathers is excellent.<
lol Mine too.

I think the Weathers was sensitive because it was a lightweight table, it was run by small clock motors.

What I'm trying to do is build the FM pickup it is famous for but for some reason a stereo version was never produced...
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Old 2nd December 2008, 02:08 AM   #7
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A single frequency two reciever system would probably work fine. The theory is easy to work out, the mechanical contrivance is another thing. The FM multiplex analogy is probably inappropriate since on an LP the left-right info is not modulated onto a higher frequency.
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Old 2nd December 2008, 03:33 AM   #8
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heh... cool

I remember the Weathers name but didn't connect the RF pickup with it.

Getting the noise down might be an issue... by modern standards.

Otoh, it is pretty cool.

have to look at the patent... and the bies.de site is excellent... geez, nice work there!

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Old 2nd December 2008, 10:04 AM   #9
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Default Brainstorming!!!!!

Quote:
The FM multiplex analogy is probably inappropriate since on an LP the left-right info is not modulated onto a higher frequency.
True. But I think the idea was to apply it to the low noise oscillators. You need two in the same cartridge for stereo but they can't interfere with each other. Right?

Quote:
the mechanical contrivance is another thing
-Maybe a simpler solution is if you can attenuate both channels with a simple foil enclosure then the foil would reflect any unwanted interference between left and right.

Basically, what's the best solution to this problem Paul Weathers ran into 50 + years ago?

Any radio hobbyists want to chime in?
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Old 2nd December 2008, 11:46 AM   #10
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My problem was moving mass versus delta C. If I got delta C to something I could reasonably demodulate, the mass got too big. The other issues (demodulation, EQ, matrixing, separation) were pretty simple.
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