Help with eliminating gyro noise on radios

Help with eliminating gyro noise on radios

Does anyone have any experience with eliminating radio noise from the turn coordinator electric gyro?  It is not a big problem over the cockpit noise in flight, but with the engine shut down, there is a very noticable hum on either radio when the gyro is spinning.  I disconnected the gyro to verify it was coming from the instrument.

I know you can purchase RFI and EMI filters from Chief or Aircraft Spruce, but don't know which would be the right one to eliminate this kind of problem.  Where would I install such a filter, in the power line to the instrument or to the radios (or the audio panel)?  I would appreciate any help or advice.

Jon

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Re: Help with eliminating gyro noise on radios

Must likely the noise comes from the ground path sharing. If the ground path from the radios audio is the same as that of the gyros the gyros ripple current will be induced into the radios. Check the ground connections of the gyros, radios and audio panel. Verify they are not tied to the same ground wire.Gyros ground path should not be shared with any of the COM/NAV or audio panel ground connections.Also check for ground wires loose or oxidized connections.

Orv

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Re: Help with eliminating gyro noise on radios

Is the noise sound a steady hum or an intermittant static sound? Some turn coordinators have a dc to 3ph converter circuit inside. this can cause a rather high pitched hum. Other TC's have commutators and brushes which may arc and cause noise.  In either case if the instrument is in good operating condition it should not radiate noise.

I would be inclined to have the instrument checked out. I doubt if a common ground is the cause of the problem, as eventually all of the grounds are common.

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Re: Help with eliminating gyro noise on radios

Regarding the installation of a noise filter. It should be installed as close to the power connection to the instrument as possible. A noise filter will reduce noise being carried on the power wire but will not eliminate noise that is radiated from the instrument.

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Re: Help with eliminating gyro noise on radios

Hi All;

Since my first post, I did some more testing and determined that the radio noise is definitely coming from the TC, but not over the wiring.  Using my handheld radio, I turned the master switch on and picked up the same noise.  The pitch changed as the gyro spooled up, and when I shut off the master switch the noise stopped.  I called Mid-Continent, the manufacturer of the unit and they are sending me an exchange unit to try.  This is the new "B" model which uses an AC motor and internal line filter to suppress noise.  I'll post the results after I install the unit.

Jon

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Re: Help with eliminating gyro noise on radios

jplaxton00 Wrote:
-------------------------------------------------------
> Hi All;
>
> Since my first post, I did some more testing and
> determined that the radio noise is definitely
> coming from the TC, but not over the wiring.
> Using my handheld radio, I turned the master
> switch on and picked up the same noise.  The pitch
> changed as the gyro spooled up, and when I shut
> off the master switch the noise stopped.  I called
> Mid-Continent, the manufacturer of the unit and
> they are sending me an exchange unit to try.  This
> is the new "B" model which uses an AC motor and
> internal line filter to suppress noise.  I'll post
> the results after I install the unit.
>
> Jon

Keep in mind that the antenna on the handheld is next to the gyro while the antenna on the radios is outside the cabin environment. A well shielded radio will not pickup noise from the panel environment. Hope the new unit fix the problem.

Orv

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Re: Help with eliminating gyro noise on radios

I just installed the new "B" model gyro and it made a big difference.  No detectable gyro noise on the panel mounted or hand-held radios.  Unit is a lot more quiet also, but you can still hear the gyro spin up so you know it is working.

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