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Am radio Hum

Discussion in 'Electronic Repair' started by Jeff Dieterle, Sep 8, 2006.

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  1. 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.
  2. Jim Lacko

    Jim Lacko Guest

    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!
  3. default

    default Guest

    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 . . .
  4. default

    default Guest

    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

    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

    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.
  5. 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
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