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Am radio Hum

J

Jeff Dieterle

Jan 1, 1970
0
On higher humidity days I get a very loud hum on the bottom end of the am
band on the radio in my garage caused by the overhead fluorescent lighting.
Is this from the tube or the ballast? On less humid days the hum is still
there but not overpowering.
 
J

Jim Lacko

Jan 1, 1970
0
If you're sure that the hum varies with humidity, you might want to consider
the idea that one of the electric utility power company's pole insulators on
your street is cracked.

You can sort-of track it down by walking down the street with a portable am
radio in hand; the radio should buzz the loudest when you're next to the
pole with the faulty insulator.

To get it fixed, call them up and make a complaint, but when will they get
around to replacing the insulator is an altogether other matter.

Good Luck!
 
D

default

Jan 1, 1970
0
On higher humidity days I get a very loud hum on the bottom end of the am
band on the radio in my garage caused by the overhead fluorescent lighting.
Is this from the tube or the ballast? On less humid days the hum is still
there but not overpowering.
Hum as opposed to buzz?

Try grounding the fluorescent reflector.

It will probably be a ground problem somewhere in the circuit. Check
for an ungrounded outlet nearby. Hard to suggest a specific thing
without knowing exactly what the circuit looks like.

You seem to have localized it to the light - turning the light off
makes the hum go away . . . Ground the reflector to a known good
ground. The light may be the obvious source of the problem but
something else may be a contributing factor.

My wife had a turntable that would buzz at the power line frequency.
I tried everything I could think of including running a wire to a
stake in the ground.

It turned out to be the missing ground on the power transformer
supplying the house. I was out mowing the lawn one day and noticed
there was no ground on the pole. I worked in power line construction
and knew it is required. It looked like someone stole the copper. I
called the power company and told them about it - they added a ground
at the pole and the turntable buzz problem was fixed.

The ground is required for the lightening arrestors on the transformer
to work - there was no argument from the company they just added a
ground the next day. Pays to look around the pole now and then - a
lightening strike can vaporize the arrestors (a collection of broken
porcelain and carbon disks around the base of the pole). Power
company will fix that too - and if they don't you can lose every
electrical thing in the house and the house . . .
 
D

default

Jan 1, 1970
0
If you're sure that the hum varies with humidity, you might want to consider
the idea that one of the electric utility power company's pole insulators on
your street is cracked.

I like that idea.

He mentions the fluorescent lamp causing the problem so I'm thinking
closer to home rather than down the street.

We had a situation like that in a rental house in San Diego - The
insulator where the overhead wire came to the house was cracked in
half and the wire was resting on the metal lag that screwed into the
house.

Seldom rains in SD. But there was a case of "dry" rot around the lag
screw. Humidity gets high (another seldom thing) and the wood in the
area gets conductive. We did have reception problems - but Radio and
TV weren't that important so we didn't try to fix it.

Had a killer rain storm one day . . . I was taking a shower and the
water kept getting hotter I kept adjusting it lower. Until I was
showering with cold water and getting burned. If I moved further from
the shower head - it felt cold - that's when the light bulb went on
and I put together the reception problems and the shower. I carefully
stepped out of the shower and left it running - wasn't about to touch
anything.

Looked outside and the area around the insulator was steaming! Told
the building owner about it. He had half the electrical system
replaced (that insulator was the only thing not up to code). He
raised the rent - we moved.
 
J

Jeff Dieterle

Jan 1, 1970
0
I don't think it's a grounding issue because the fixtures are connected with
emt and that is grounded at the service panel. I have 3 banks of 8'
fixtures, 4 two-tube fixtures in each bank. Two of the banks cause no
problems. When I can get some of junk cleaned out of the garage I'll pull
the tubes one at a time till the hum dies,and start t-shooting at that
fixture.
 
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