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Thread: Radio Noise

  1. #1

    Radio Noise

    Try this:
    Take the antenna off of a cheap am radio (many have a screw to take
    out), put the tuner anywhere in the middle of the band, while using
    ear phones. Take off the cowl and have somebody trusty holding the
    brakes while still tied down. Start the motor and use the radio as
    a "sniffer" around each of the plug wires, engine grounding strap,
    strobe(s), instrument panel, and rest of the plane. This will
    usually find emi emmitters, as most are broad-spectrum. (Taking the
    antenna off an Icom hand-held tuned to 121.5 is also how to find a
    single airplane with an ELT running on a crowded ramp.)

    If the am radio finds nothing, suspect unshielded wiring or
    similar. Pull all the breakers and start adding loads one by one
    till something happens. Oh, and some naive technicians will ground
    shielding at BOTH ends, which is a no-no.

    Bob
    A&P, Aero Eng

    (--- In musketeermail@yahoogroups.com, Paul Werbin
    <paulwerbin@y...> wrote:
    >
    > I have just finished up with the third visit from some Bendix
    King - Honeywell engineers trying to eliminate noise that is
    interfering with my radios and Datalink. We have tried all the usual
    things- turning off alternator, Txpdr, scope, etc etc etc in flight
    and on the ground. The noise seems to appear upon takoff on an
    occilloscope. The engineer guys are baffled and are suggesting
    replacing the electrical bonding straps on the control surfaces.
    >
    > Has anyone out there had similar problems and found something
    specific to out airframes? It doesn't seem to be usual culprits...
    >
    > Thanks for any help.
    >
    > Paul
    >
    >
    >
    >
    > ---------------------------------
    > Yahoo! Sports
    > Rekindle the Rivalries. Sign up for Fantasy Football
    >
    > [Non-text portions of this message have been removed]




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  2. #2

    Radio Noise

    Two additional thoughts on my last post:
    1) When I mentioned adding loads one by one, that included running
    the engine on each mag, singly.
    2) When using a hand-held with the antenna removed to find a running
    ELT, you need to get within about 5 feet of the elt antenna on each
    plane.
    Bob
    --- In musketeermail@yahoogroups.com, "Bob Swaim" <dswaim1119@c...>
    wrote:
    > Try this:
    > Take the antenna off of a cheap am radio (many have a screw to
    take
    > out), put the tuner anywhere in the middle of the band, while
    using
    > ear phones. Take off the cowl and have somebody trusty holding
    the
    > brakes while still tied down. Start the motor and use the radio
    as
    > a "sniffer" around each of the plug wires, engine grounding strap,
    > strobe(s), instrument panel, and rest of the plane. This will
    > usually find emi emmitters, as most are broad-spectrum. (Taking
    the
    > antenna off an Icom hand-held tuned to 121.5 is also how to find a
    > single airplane with an ELT running on a crowded ramp.)
    >
    > If the am radio finds nothing, suspect unshielded wiring or
    > similar. Pull all the breakers and start adding loads one by one
    > till something happens. Oh, and some naive technicians will
    ground
    > shielding at BOTH ends, which is a no-no.
    >
    > Bob
    > A&P, Aero Eng
    >
    > (--- In musketeermail@yahoogroups.com, Paul Werbin
    > <paulwerbin@y...> wrote:
    > >
    > > I have just finished up with the third visit from some Bendix
    > King - Honeywell engineers trying to eliminate noise that is
    > interfering with my radios and Datalink. We have tried all the
    usual
    > things- turning off alternator, Txpdr, scope, etc etc etc in
    flight
    > and on the ground. The noise seems to appear upon takoff on an
    > occilloscope. The engineer guys are baffled and are suggesting
    > replacing the electrical bonding straps on the control surfaces.
    > >
    > > Has anyone out there had similar problems and found something
    > specific to out airframes? It doesn't seem to be usual culprits...
    > >
    > > Thanks for any help.
    > >
    > > Paul
    > >
    > >
    > >
    > >
    > > ---------------------------------
    > > Yahoo! Sports
    > > Rekindle the Rivalries. Sign up for Fantasy Football
    > >
    > > [Non-text portions of this message have been removed]




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