An MD80's TCAS processor severely disrupted VHF radio reception on frequency 128.0.

Attributes
ACN	811078
Time
Date	200811
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 12000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : zzz.tracon
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 210 flight time total : 14000 flight time type : 7500
ASRS Report	811078
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	aircraft equipment other aircraft equipment : vhf reciever other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : regained aircraft control
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Upon switching to frequency 128.0 the frequency was broadcasting a noise which can only be described as someone keying the microphone next to a running vacuum cleaner. I attempted to contact approach but was able to understand very little of what was said. We attempted to use the #2 radio but encountered the same problem. Suspecting electronic interference I made a PA telling the passenger to turn off all electronic devices immediately. This did not help. I returned to the previous frequency and reported the problem. I was instructed to return to frequency 128.0 as there was not problem on their end. The same interference was still quite evident however I was able to understand the controller and continued to an uneventful landing. After gate arrival I removed power from the right electrical bus and the problem went away. It was obviously a component of our airplane that was causing the problem. The following are the logbook entries related to this problem. Isolated to TCAS processor interference replace TCAS processor. Performed required checks.

Original NASA ASRS Text

Title: AN MD80'S TCAS PROCESSOR SEVERELY DISRUPTED VHF RADIO RECEPTION ON FREQUENCY 128.0.

Narrative: UPON SWITCHING TO FREQ 128.0 THE FREQUENCY WAS BROADCASTING A NOISE WHICH CAN ONLY BE DESCRIBED AS SOMEONE KEYING THE MIC NEXT TO A RUNNING VACUUM CLEANER. I ATTEMPTED TO CONTACT APCH BUT WAS ABLE TO UNDERSTAND VERY LITTLE OF WHAT WAS SAID. WE ATTEMPTED TO USE THE #2 RADIO BUT ENCOUNTERED THE SAME PROB. SUSPECTING ELECTRONIC INTERFERENCE I MADE A PA TELLING THE PAX TO TURN OFF ALL ELECTRONIC DEVICES IMMEDIATELY. THIS DID NOT HELP. I RETURNED TO THE PREVIOUS FREQUENCY AND RPTED THE PROBLEM. I WAS INSTRUCTED TO RETURN TO FREQUENCY 128.0 AS THERE WAS NOT PROBLEM ON THEIR END. THE SAME INTERFERENCE WAS STILL QUITE EVIDENT HOWEVER I WAS ABLE TO UNDERSTAND THE CTLR AND CONTINUED TO AN UNEVENTFUL LNDG. AFTER GATE ARR I REMOVED POWER FROM THE R ELECTRICAL BUS AND THE PROBLEM WENT AWAY. IT WAS OBVIOUSLY A COMPONENT OF OUR AIRPLANE THAT WAS CAUSING THE PROBLEM. THE FOLLOWING ARE THE LOGBOOK ENTRIES RELATED TO THIS PROBLEM. ISOLATED TO TCAS PROCESSOR INTERFERENCE REPLACE TCAS PROCESSOR. PERFORMED REQUIRED CHECKS.

Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.