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joewho
Premium Member
join:2004-08-20
Dundee, IL

joewho

Premium Member

[Electrical] laptop power supply

Using a small laptop in the garage to pipe music to the stereo. When it's plugged in all the radio stations have static. Since we live on low ground, I ran a wire to the attic and the stations all come in clear, just to get static from the laptop. Any helpful advice? The connection on the stereo for the antenna is a cable (rg) types, but no threads, you just push it on, and it didn't work. I wrapped black tape around the outside, so just the center pin connects and it works good, but it's a mickey mouse way to go.

SparkChaser
Premium Member
join:2000-06-06
Downingtown, PA

SparkChaser

Premium Member

If you unplug the power supply and run on batteries, does the interference go away?

You're talking FM band radio?

Where's the antenna cable go to, the attic? Is there and antenna there?
joewho
Premium Member
join:2004-08-20
Dundee, IL

joewho

Premium Member

Unplugged, everything is fine. I keep forgetting about it, wonder what happened, then remember to unplug the computer.

Ran the cable wire to the attic, without antenna, and all the stations came it, but while up there I found some little antenna and connected to it. A little better yet, but could do without it. We live near a river, so were down low. But about 40 miles from chicago.

cowboyro
Premium Member
join:2000-10-11
CT

cowboyro to joewho

Premium Member

to joewho
Move the power supply and/or laptop further away.

SparkChaser
Premium Member
join:2000-06-06
Downingtown, PA

SparkChaser to joewho

Premium Member

to joewho
^^^^this

Or try another outlet.

Ungrounding the coax you have a wire running through the house and picking up anything that's on the power lines. Ideally you should have a coax running up to an FM antenna in the attic.

davidg
Good Bye My Friend
MVM
join:2002-06-15
00000

1 edit

davidg to joewho

MVM

to joewho
it is a ground loop, you either have a bad ground or a different ground or a bad cable.

one other thing I've seen cause this is a hot/neutral swap at the outlet. we used to carry a shaved 2 prong adapter so if we ran into this setting up a sound board for an even we could just flip the adapter around. all you have to do is shave the wide prong to the same width as the narrow prong.
joewho
Premium Member
join:2004-08-20
Dundee, IL

joewho to SparkChaser

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to SparkChaser
Spark, the way it's set up, stations come in. Not using tape on the stereo, I get nothing. That's the ground? Essentially, I should take off the tape and find something for the other end of the rg cable to screw into? So, it would be grounded at both ends?
I really don't like this type of plug. You can't use a radio antenna wire that you just pin to the wall.

There are 2, 4 plug boxes in the garage. Same issue with either box, I use an electric heater, guitar amplifer and other electronics. Only the computer ps and cordless drill charger cause the issue. Thanks for the replies.

I just wonder, if I use the plug properly and somehow ground one wire to a nail or something like that? Is that the principle here?

StillLearn
Premium Member
join:2002-03-21
Streamwood, IL

StillLearn to joewho

Premium Member

to joewho
When the laptop is running off of battery, there is no interference, right?

Consider using an AC RFI/EMI filter. This can be done with something like the method in »www.ky-filters.com/ac.htm or you could buy a plug-in filter for the purpose. I don't find an inexpensive commercial filter to suggest, but they are probably available.

nunya
LXI 483
MVM
join:2000-12-23
O Fallon, MO

1 recommendation

nunya to joewho

MVM

to joewho
It's not a ground loop. It's RFI. The same thing happens with commercial ballasts and FM radio.

SparkChaser
Premium Member
join:2000-06-06
Downingtown, PA

3 edits

SparkChaser to StillLearn

Premium Member

to StillLearn
said by StillLearn:

Consider using an AC RFI/EMI filter. This can be done with something like the method in »www.ky-filters.com/ac.htm or you could buy a plug-in filter for the purpose. I don't find an inexpensive commercial filter to suggest, but they are probably available.

I think the interference is conducted and the toroid won't do much. A line filter be worth a try.

Edit: It's been decades since I worked on an antenna. If you google FM antenna you'll see some you can make or buy. Just don't make the one with the twin lead, from the sound of your problem you need the coax. Maybe tschmidt See Profile will chime in he playing with antennas these days.

Edit2: I previously ask if this was AM or FM. I'm not sure I got an answer. An experiment here doesn't give me much FM interference

Thespis
I'm not an actor, but I play one on TV.
Premium Member
join:2004-08-03
Keller, TX

Thespis to joewho

Premium Member

to joewho
The hum is coming from your laptop power supply. It's a common problem when using the onboard sound card in laptops. The best solution is a USB audio device. A passive DI box with a ground lift switch and some adapters would also solve the problem.
»www.amazon.com/s/ref=nb_ ··· +d%2Caps
A power supply without a ground pin might also do the trick.

Termites
@174.64.136.x

Termites

Anon

Use Quad Shielded wire.
Hellrazor
Bah Humbug
join:2002-02-02
Abyss, PA

Hellrazor to nunya

Member

to nunya
said by nunya:

It's not a ground loop. It's RFI. The same thing happens with commercial ballasts and FM radio.

Have that fun with my t5 fixtures and my radio in my office at work. The weirdest thing I found is placing the radio directly under the light stops the interference. Since the t5 are indirect lighting fixtures, there must be more metal on the bottom or something.
TheMG
Premium Member
join:2007-09-04
Canada
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TheMG

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said by Hellrazor:

Have that fun with my t5 fixtures and my radio in my office at work. The weirdest thing I found is placing the radio directly under the light stops the interference. Since the t5 are indirect lighting fixtures, there must be more metal on the bottom or something.

If the radio has a typical vertical whip antenna, the weakest reception is at the tip of the antenna, whereas the strongest reception will be horizontally on any side of the antenna.

By placing the radio directly below the light, you're essentially putting the interference source in the spot where the antenna has the weakest reception of that interference.