Picking Up Unwanted Radio Signal Through System

0 Members and 1 Guest are viewing this topic. Read 3960 times.

Bob in St. Louis

  • Volunteer
  • Posts: 13259
  • "Introverted Basement Dwelling Troll"
Re: Picking Up Unwanted Radio Signal Through System
« Reply #20 on: 17 Jan 2015, 10:01 pm »
I have no intelligence to offer (so you can stop reading, unless you're in the mood for a neat story).

About 40 years ago, my family and I moved to a house in Wentzville Missouri near highway 70 (Major thoroughfare across the country). One night, not long after we moved in, we heard voices throughout the entire house. It raised the hair on the backs of our collective necks. All wide eyed and in pure shock, almost like God himself was talking, none of us had a clue as to what we just heard. The "voice" happened may times over random days and at weird times for many years. One day, My Father figured out that it was truckers with "hotrod" CB radios traveling down highway 70 that were being picked up by the whole house intercom system. Funny thing was, the "system" didn't have a head unit (was removed before we moved in), but every room in the house had an in-wall speaker. Somehow the the signal was "just right" the house picked it up and broadcast it in every room. It was pretty creepy, especially when you were a small child.


rodge827

Re: Picking Up Unwanted Radio Signal Through System
« Reply #21 on: 17 Jan 2015, 10:07 pm »
 Bob, That's crazy and creepy for sure!  :lol:


Speedskater

  • Full Member
  • Posts: 2733
  • Kevin
Re: Picking Up Unwanted Radio Signal Through System
« Reply #22 on: 17 Jan 2015, 10:55 pm »
All cables, be they signal, control, speaker or AC power can act as interference antennas (some are transmitting most others are receiving).  It is good to twist all unshielded multi-conductor cables. Now it's 2015 and almost any new product in your home (or your neighbors) has the potential to transmit interference.

Jim Brown is the go-to expert when it comes to interference. His day job is audio consulting but his hobby is Ham radio, so he knows both sides of the story.

Start with:
"RF Interference in Audio Systems"
http://www.audiosystemsgroup.com/AES-RFI-SF08.pdf

"RFI, Ferrites, and Common Mode Chokes For Hams"
don't let the 'Hams' fool you, much applies to audio systems.
http://www.audiosystemsgroup.com/RFI-Ham.pdf

50 more good papers:
http://www.audiosystemsgroup.com/publish.htm

dB Cooper

Re: Picking Up Unwanted Radio Signal Through System
« Reply #23 on: 17 Jan 2015, 11:23 pm »
Yeah, you could try wrapping the ICs in aluminum foil and touching one end of the foil to the ground connection on the IC cable.
Sounds a lot like....shielding.  :roll:

DaveC113

  • Industry Contributor
  • Posts: 4352
  • ZenWaveAudio.com
Re: Picking Up Unwanted Radio Signal Through System
« Reply #24 on: 18 Jan 2015, 12:12 am »
Sounds a lot like....shielding.  :roll:

Thanks for the sarcasm!  :thumb: I do make cables for a living and I'm actually quite good at it.  :green:  I make shielded cables for phono use on a custom basis, so I have made quite a few shielded cables. Most of the time though, it's not necessary and adds bulk, stiffness, complexity and expense to cables all while slightly dulling the high frequencies. Shielded cables that have the least effect on the sound end up being quite large in diameter. Anyway, there's plenty of highly regarded cables both shielded and unshielded. I am trying to make cables that are high value so I don't want to add complexity and expense if it's not required. This also follows my KISS principle.

I suggested doing this so he doesn't have to find or purchase shielded cables to see if the cables are the culprit... but as I said, if it wasn't picking it up before it's not likely to be the problem.

The cause can be mysterious, as I said it happened to me and simply cycling the power off and back on got rid of it.  :scratch:

Folsom

Re: Picking Up Unwanted Radio Signal Through System
« Reply #25 on: 18 Jan 2015, 12:29 am »
Huge changes in potentials can make RF and noise spew from a shielded system. Why with gear on/off? That I'm not sure, could be coincidental.

dB Cooper

Re: Picking Up Unwanted Radio Signal Through System
« Reply #26 on: 18 Jan 2015, 04:39 am »
Thanks for the sarcasm!  :thumb: I do make cables for a living and I'm actually quite good at it.  :green:  I make shielded cables for phono use on a custom basis, so I have made quite a few shielded cables. Most of the time though, it's not necessary and adds bulk, stiffness, complexity and expense to cables all while slightly dulling the high frequencies. Shielded cables that have the least effect on the sound end up being quite large in diameter. Anyway, there's plenty of highly regarded cables both shielded and unshielded. I am trying to make cables that are high value so I don't want to add complexity and expense if it's not required. This also follows my KISS principle.

I suggested doing this so he doesn't have to find or purchase shielded cables to see if the cables are the culprit... but as I said, if it wasn't picking it up before it's not likely to be the problem.

The cause can be mysterious, as I said it happened to me and simply cycling the power off and back on got rid of it.  :scratch: