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Chuckaluphagus
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My cat is a radio transmitter?

Thu Oct 18, 2018 7:55 pm

Nope, I'm not wearing a tin foil hat, but I am having a confounding audio experience.

As I'm petting my cat here next to my desk, I'm producing static discharge from my hand to her ear every time I bring my hand back up to pet her again. And every time the static zap happens, I feel it in my hand and my speakers go "pop".

To be clear, my cat is not part of the audio setup. She's not even in contact with any part of the audio setup. She is sitting on an ottoman that's right up against the wooden table upon which the stereo receiver sits, and the distance between them is only about 10 inches (25 cm), but ... seriously?

I figure my cat isn't really transmitting, but that instead I have a really, really weird antenna being formed somewhere in the web of cables and speaker wire that currently connect my desktop and laptop computers to the same receiver, and I'm picking up the radio noise of the static zap. I just moved my entire office around a few months ago, and therefore also redid the whole audio setup, but this is the first time I've encountered this phenomenon here or elsewhere. My cat seems blasé about the whole thing, of course.
 
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Re: My cat is a radio transmitter?

Thu Oct 18, 2018 8:01 pm

ESD discharges emit noise into the RF regions, and pretty much any wire that feeds an audio circuit can act as a crude AM radio antenna and inject it into the amplifier circuit.

The same effect can be observed with analog radio (and analog TV, when that was still a thing) during a thunderstorm.
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Re: My cat is a radio transmitter?

Thu Oct 18, 2018 8:05 pm

When the static discharges happen, you and your cat are acting as transmitting antennae, and radiating low-energy broadband radio noise. Something in the maze of cables is acting as a receiving antenna and picking this interference up.

Sounds like time to upgrade to some cables with better shielding, and/or add some ferrite rings to the cabling where they enter/exit the various components!

You could try selectively disconnecting the desktop and laptop connections to see if one or the other is the culprit.

Interesting experiment: Try grounding yourself to the desktop case while petting the cat. Does that make it better, worse, or have no effect?

Edit: Geeky trivia: You can get an NE-2 style neon lamp to flash with static electricity. I remember playing around with this as a budding electronics/computer geek when I was young.
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chuckula
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Re: My cat is a radio transmitter?

Thu Oct 18, 2018 8:35 pm

The most primitive spark gap radios operated on similar principles.
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Re: My cat is a radio transmitter?

Fri Oct 19, 2018 6:56 am

chuckula wrote:
The most primitive spark gap radios operated on similar principles.


Winner!!!

Your cat is acting is like a spark gap transmitter! :D
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Re: My cat is a radio transmitter?

Sun Nov 04, 2018 4:40 pm

Chuckaluphagus wrote:
Nope, I'm not wearing a tin foil hat, but I am having a confounding audio experience.

As I'm petting my cat here next to my desk, I'm producing static discharge from my hand to her ear every time I bring my hand back up to pet her again. And every time the static zap happens, I feel it in my hand and my speakers go "pop".

To be clear, my cat is not part of the audio setup. She's not even in contact with any part of the audio setup. She is sitting on an ottoman that's right up against the wooden table upon which the stereo receiver sits, and the distance between them is only about 10 inches (25 cm), but ... seriously?

I figure my cat isn't really transmitting, but that instead I have a really, really weird antenna being formed somewhere in the web of cables and speaker wire that currently connect my desktop and laptop computers to the same receiver, and I'm picking up the radio noise of the static zap. I just moved my entire office around a few months ago, and therefore also redid the whole audio setup, but this is the first time I've encountered this phenomenon here or elsewhere. My cat seems blasé about the whole thing, of course.


Can you borrow me your cat for a weekend? Have a bad connection right here

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