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Author Topic: Is it the "on-ness" that makes noise?  (Read 256 times)
K7NHB
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Posts: 226




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« on: December 24, 2005, 06:01:03 PM »

I've read that lights with dimmer controls, Fluorescent lamps, and wall warts create RX noise. Sorry if this is so dumb, but do they have to be On or just exist in the AC line to cause a problem?

I mean obviously, if something is switched out, it electrically doesn't exist. But these day, merely "off" doesn't mean it is out of the circuit.

I can hear a large noise spike on my battery MW radio about 2500 KHz, but could not trace to anything specific when walking around the house. When I went outside, about 10 feet from the house, the radio was quiet.

So I figured that because the outside antenna was 20 feet from the house, I wouldn't be picking up any of that "interior" noise anyway.

Is that right or should I spend the time to trace the noise source down? When I opened a switch on the circuit breakers, the noise went away, so it is findable. But if it is from built in light fixtures, I can't do much about it anyway.

Thank you for your comments and advice.
73,
Paul
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N6AJR
Member

Posts: 9913




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« Reply #1 on: December 24, 2005, 06:55:44 PM »

some of these make noise all the time, find it and replace the offender and enjoy..
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AA8LL
Member

Posts: 400




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« Reply #2 on: December 24, 2005, 07:09:18 PM »

Some things are always on, like doorbell transformers, aquarium heaters, furnace thermostats, and switching power supplies for modern lighting and electronics.  Why don't you connect to your outside antenna and see if the noise bothers your normal operating?  There was a teenaged ham on here a few years ago that had under-cabinet "puck" lights installed in the family kitchen.  They completely wiped out his hf operation but the noise went away by turning them off.  The family didn't want to turn them off when he was operating.  They were purty.  If you are an adult and don't live in an institution, you can make the noise stop if you are persistent.  If it bothers you, find it, and fix it.
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K7NHB
Member

Posts: 226




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« Reply #3 on: December 25, 2005, 12:12:17 AM »

Thank you for the replies. I went around the house with the radio again and found that though the torch lamps (dimmer) and dimmer dining room light make noise, they only make noise when On - that can be controlled.

Unfortunately, the 15 inch Compaq LCD monitor, used for digital modes, also genrates noise - at least when run from it's AC (switching supply) line. I can run it from batteries and put some chokes on the monitor line. Had to  take my "ham software" computer off line for a while - so I"ll be sure to check that too.

If I can drop the noise level down and S unit or two - who knows what I'll find underneath.

73,
Paul
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WD8PTB
Member

Posts: 671




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« Reply #4 on: December 25, 2005, 05:03:24 AM »

Almost everything electronic makes noise. Lisen to the offending signal on your radio and have someone unplug the suspected item. Moving your ham antenna away from the house will help a lot.Our touch lites made noise all the time,even if the light was off. Usualy flat panel monitors are quieter that tube type. Good luck; Don WD8PTB
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HA5RXZ
Member

Posts: 380




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« Reply #5 on: December 25, 2005, 05:21:29 AM »

1) the torch lamps (dimmer) and dimmer dining room light make noise, they only make noise when On. First you can try putting a 220v rated capacitor across the dimmer, MAKE SURE of the rating when you do this, if in doubt, ask. You can also try an RF choke in series with both leads, the rating of the choke in amps depends on your lighting load.

2) Unfortunately, the 15 inch Compaq LCD monitor, used for digital modes, also genrates noise - at least when run from it's AC (switching supply) line. The first thing you need to do is find out if it is the power supply or the monitor which is creating the RF noise, test by running the power supply into a resistor as a dummy load. The easiest cure for this is to run the AC power cord and/or the monitor power through a ferrite ring a few times to form a common mode choke. If that doesn't work then try earthing the chassis of the LCD monitor to AC ground through a 10K ohm resistor

Happy Christmas!

HA5RXZ
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KL7IPV
Member

Posts: 984




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« Reply #6 on: December 25, 2005, 03:12:44 PM »

Quote:
"2) Unfortunately, the 15 inch Compaq LCD monitor, used for digital modes, also genrates noise - at least when run from it's AC (switching supply) line. The first thing you need to do is find out if it is the power supply or the monitor which is creating the RF noise, test by running the power supply into a resistor as a dummy load. The easiest cure for this is to run the AC power cord and/or the monitor power through a ferrite ring a few times to form a common mode choke. If that doesn't work then try earthing the chassis of the LCD monitor to AC ground through a 10K ohm resistor "

You can also change the refresh rate for the display. Go to the control panel and then to display and settings to find the refresh rate. It may be changeable from 60Hz to 72Hz or another that wont eat your radio.
Good luck
Frank
KL7IPV
 
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K1CJS
Member

Posts: 5981




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« Reply #7 on: December 25, 2005, 05:03:06 PM »

Don't forget to check your electronics around the house.  Some of the TVs, Disk players, radios, heck--just about any home electronic unit IS ALWAYS ON, on standby.  Most of these things are RF quiet, but if something starts to go it can cause noise on the house wiring.

I had a small cheapo TV that I found to be the cause of some RF even when it was off-that is, on standby.  When it was unplugged the noise vanished.  Oh, and don't forget cordless phones, sometimes those things are the worst!  Good luck!
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WA9SVD
Member

Posts: 2201




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« Reply #8 on: December 27, 2005, 01:42:32 AM »

ANYTHING that uses a remote will be in the "always on" category.  But many "wall warts" are not a major problem; they are just a transformer and a rectifier and perhaps a capacitor to filter the DC.  However, items such as computer printers, scanners, routers, ethernet hubs, WiFi terminals, cable boxes, cable modems, DSL modems, battery chargers, and any battery operated device with a "smart charger" can be a potential problem.   All you can do is eliminate one at a time, including the not-so-obvious items, like the lawn trimmer that has a charger, the electric drill charger, you have to consider and eliminate everything.  Good luck!
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