My shop has overhear florescent lights. this lights create lots of noice on the AM band. what can I do to cut down this noise. Thanks, Bud

You're not gonna like the answer Bud. There are only a few options.

Use incandescent lighting for your bench and kill those over head florescent lights....maybe get a couple of those articulatined arm or gooseneck lamps.

OR:

Rewire your bench area so that your bench is powered from a different circuit than those lights.

Another nasty source of interference is dimmer switches. The dimmer the lighting, the louder the buzz they generate.

I was thinking though..........perhaps an isolated power supply for your project radio would eliminate the problem as well......not sure about that though. Hopefully some of the other members will jump in here.

wish I could edit posts.......... I believe the correct spelling is "articulated".......dang typos.

Bud,
As far as I'm concerned, flourescent lights are lightning in a tube. They constantly arc at the 60Hz line frequency. The only way to contain the RF energy is to turn them off or put a steel tube around them, but the darkness is hard to work under. Even in darkness, your neighbors wireless network, lights, microwave, TV, stereo, cell phone, cordless handset will still get in. Good AM is hard to come by, unless you live close to a 50KW power house that broadcasts your kind of entertainment.

marv

:My shop has overhear florescent lights. this lights create lots of noice on the AM band. what can I do to cut down this noise. Thanks, Bud

Place a .1 MFD condenser across the AC wiring on each fluorescent. See if this works. If not, purchase some 100 mH chokes from Radio Shack (ferrite rod with two layers of wire). Place one on each side of the AC line for each fluorescent. All components should be inside of the fluorescent housing. Try set-up with a .1 MFD condenser before and after the chokes, across the AC wiring. Experiment with just one before or just one after. See if one way or the other or both works best for you. You can also try two .1 MFD units in series on each side of the chokes, with their center junction tied to the metal housing of the fluorescent. Again, try this on the fluorescent side of the chokes, on the AC side of the chokes, and then on both sides, to see which way cuts out noise the most.

Thomas

Thomas,
As noted in a post several months ago, the flourescent tubes are only part of the problem, and its primarily radiated energy, not power line induced. I walked through my entire house with a portable AM set, and found a lot of contributing radiation sources. Maybe I should just work in the dark, and avoid the many mistakes I make in a well lit area. lol!!

marv

:Place a .1 MFD condenser across the AC wiring on each fluorescent. See if this works. If not, purchase some 100 mH chokes from Radio Shack (ferrite rod with two layers of wire). Place one on each side of the AC line for each fluorescent. All components should be inside of the fluorescent housing. Try set-up with a .1 MFD condenser before and after the chokes, across the AC wiring. Experiment with just one before or just one after. See if one way or the other or both works best for you. You can also try two .1 MFD units in series on each side of the chokes, with their center junction tied to the metal housing of the fluorescent. Again, try this on the fluorescent side of the chokes, on the AC side of the chokes, and then on both sides, to see which way cuts out noise the most.
:
:Thomas

True, true, but I have had a lot of luck with filters on the fluorescent line. As I said before, the filters must be experimentally applied. One filter doesn't necessarily work well in all cases. Start with one condenser. Elaborate from there.

Thomas

Thomas.
OK, here is my problem. As a matter of convenience with only 1 unswitchable wall outlet available in my garage and the need for 3 overhead shop lights, I devised a scheme to use 2 conductor zip cord extensions with the clamp on in-line swithes. The shop lights I purchased several years ago had 6 inch 3 wire power cords, so the safety grounds were never connected. I could take down the lights and install switches in each cover, which I did just yesterday at my radio workbench, but would have to purchase 2 new 3 wire extension cords just so I could test AM radios in a lighted garage, aside from the remainder of my home which is a plethora of RFI.

marv

:True, true, but I have had a lot of luck with filters on the fluorescent line. As I said before, the filters must be experimentally applied. One filter doesn't necessarily work well in all cases. Start with one condenser. Elaborate from there.
:
:Thomas

Ground the fluorescents. Try Norm's idea of a hardware mesh over the tubes (grounded to the metal chassis). Then try various filter techniques.

I can usually make fluorescents very silent. The solid state ones are the worst. Also, it's a good idea to make use of the external antenna wire on all radios, even if equipped with loops. I can get fairly static-free reception in my parents' basement, though, with tons of fluorescents and steel furnace pipes, and I haven't even done anything to their fluorescents. The one solid state unit towards one end of my dad's bench makes a bit of noise, but the others are pretty quiet. I'm sure that with some filtering, I could make things silent.

Thomas

Well Thomas,
Got a new one for ya. My DMM setting about 18 inches under a new shop lite on my radio bench, and measuring low value caps. ie 67pf, 82pf. With the light on, meter will dance as much as 5pf, but off the reading is rock solid. Just installed the light with the 3 wire cord set. I know that the DMM's must use an AC signal to measure capacitors, but why would 60Hz radiation interfere?

marv

:Ground the fluorescents. Try Norm's idea of a hardware mesh over the tubes (grounded to the metal chassis). Then try various filter techniques.
:
:I can usually make fluorescents very silent. The solid state ones are the worst. Also, it's a good idea to make use of the external antenna wire on all radios, even if equipped with loops. I can get fairly static-free reception in my parents' basement, though, with tons of fluorescents and steel furnace pipes, and I haven't even done anything to their fluorescents. The one solid state unit towards one end of my dad's bench makes a bit of noise, but the others are pretty quiet. I'm sure that with some filtering, I could make things silent.
:
:Thomas

Well, because it's AC. A capacitor meter measures capacitance by passing an AC frequency through it. The more the frequency passes through, the lower the value of the condenser.

Thomas

Wouldn't think 60 Hz would have much effect on a 67pf cap, but maybe the 24 inch leads are a contributor

marv

:Well, because it's AC. A capacitor meter measures capacitance by passing an AC frequency through it. The more the frequency passes through, the lower the value of the condenser.
:
:Thomas

Possible. 60 cycles probably wouldn't normally affect a 60 something pf condenser. What happens when your leads are moved around? Do they have thick enough insulation? The 60 cycles isn't affecting the condenser, though. It's simply radiating directly into the leads. I don't have much experience with capacitance meters (though I really want to buy a Solar one some day...old, with eye tube and meter, in a wooden box). However, I assume that a capacitance meter simply has a signal source and then a device that detects the signal passage (say, an amplifier, which drives the meter through a detector (diode) of sorts that converts the signal to DC for the meter). If this is the way the design works, then all that is needed is for stray alternating current to get into the detection lead. What happens when you grab each of the leads separately? Does one make the meter swing up?

T.

Thomas,
I just turn off the flourescent and use a flashlight for low values, since I know the symptoms. Various lead configurations ie over metal etc alters readings. I only use the leads for components still in circuit with 1 lead disconnected, but for new stuff, just prior to install, I'll use the socket on the instrument. I'm having too much fun with radios, and never cared much for power engineering antway. It doesnt have any effect on large values, and I suppose a less sensitive scale. I have a restored (myself) Solar CB in a mahogany case with the eye, no meter, but not for sale. It belonged to my older brother along with a Superior TV-11 tube tester, which became mine after his passing in '01. Sort of a family heirloom, if you will. The Solar is not as accurate or handy as my B & K, and a bit more bulky, except for high voltage tests. I'm just living with it.

marv

:Possible. 60 cycles probably wouldn't normally affect a 60 something pf condenser. What happens when your leads are moved around? Do they have thick enough insulation? The 60 cycles isn't affecting the condenser, though. It's simply radiating directly into the leads. I don't have much experience with capacitance meters (though I really want to buy a Solar one some day...old, with eye tube and meter, in a wooden box). However, I assume that a capacitance meter simply has a signal source and then a device that detects the signal passage (say, an amplifier, which drives the meter through a detector (diode) of sorts that converts the signal to DC for the meter). If this is the way the design works, then all that is needed is for stray alternating current to get into the detection lead. What happens when you grab each of the leads separately? Does one make the meter swing up?
:
:T.