Tommy Posted November 18, 2014 Report Posted November 18, 2014 Hi everyone! My KX175BE TSO radio suffers from a constant middle pitch static noise - only on higher frequencies - anything higher than 120MHz. Changing RPM or any other electrical components have no impact on it EXCEPT when I turn on my AvMap (charged thru the cigarette lighter charging port), the noise gets significantly less. Transmission and receiving are both normal Just wondering what would've be the likely causes? Thanks
FBCK Posted November 18, 2014 Report Posted November 18, 2014 I have an 1981 231 and had a similiar issue with 155, I had the voltage regulator replaced with a Zeftronics one and the high pitched noise went away.
Mooneymite Posted November 18, 2014 Report Posted November 18, 2014 Is it present on the ground and in flight? Is it present when the engine is not running? (Hopefully on the ground ) Is it present when all headsets are disconnected (on speaker)? Tried disconnecting all mic's? Can you easily switch antennas? You might see if the noise moves with the antenna connection. Keep trying various combinations of radio/mic switches, see if it makes any difference. I once had a persistent "rattle-sound" in my headset that turned out to be a VOR mixer switch....static can also be associated with broken grounding straps. Good luck. 1
bonal Posted November 18, 2014 Report Posted November 18, 2014 Could be tennitus, Its driving me CRAZY 3
Jerry 5TJ Posted November 19, 2014 Report Posted November 19, 2014 One Possibility: Is the AvMap connected to the audio panel and is there a chance that when it is powered on the audio line is loaded down, causing less speaker/headphone amplitude from the KX170? Another thought: The KX170BE selects Comm (and Nav) frequencies with a multi-section rotary switch that programs a clever but antique digital phase lock loop synthesizer. Make careful note of the frequencies (MHz and KHz knobs both) of the affected channels. That may point your avionics technician towards a problem with the frequency synthesizer. For instance there is a change (M0 bit) between 119 and 120 MHz so if the noise is present at and above 120 but not at 119 it could be that switch wafer contact giving problems. 2
Tommy Posted November 19, 2014 Author Report Posted November 19, 2014 Hmm.. lots of possiblity! Back to the hangar I go! Thanks guys!
WardHolbrook Posted November 19, 2014 Report Posted November 19, 2014 Hi everyone! My KX175BE TSO radio suffers from a constant middle pitch static noise - only on higher frequencies - anything higher than 120MHz. Changing RPM or any other electrical components have no impact on it EXCEPT when I turn on my AvMap (charged thru the cigarette lighter charging port), the noise gets significantly less. Transmission and receiving are both normal Just wondering what would've be the likely causes? Thanks I see you're in Australia, that could be problematic. Those units were never meant to be operated upside down. 5
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