Narrative:

In our EMS helicopter we have been getting interference on 130.0 (VHF am), while using a patient heart monitor. The interference has been in the form of an approximately 1000 cps tone received over the VHF radio(south) (we have 2 in our helicopter). During a short flight from a hospital just north of XXX, to our hospital 13 NM west, the interfering tone was practically continuous and quite distracting to pilot's thinking, as well to his reception of tower transmission. Just after takeoff I contacted XXX tower, received instructions to squawk XXXX and clearance to depart the TCA at or below 2400', which I acknowledged and complied with. Now, however, the interference was so loud on tower frequencys (135.0 and 120.0 [ZZZ]) that I inadvertently turned my tower vol control so low that I could not hear XXX tower at all. My attention, since we were already west of XXX traffic, was directed at traffic approaching ZZZ from the northeast (crossing from right to left, ahead of me). As I was entering ZZZ's control zone 5 NM ene, I told XXX tower I was going to change to ZZZ tower, since I had traffic in sight on the approach to ZZZ 23L. Hearing no response, I shifted to ZZZ, told tower I had traffic in sight. Hearing no response, I glanced at VHF control, turned up vol and called again. They had heard first call and told me that our radio interference was not going out over the air. Since incident I am working with mfr to see how we can eliminate the problem of noise interference.

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Original NASA ASRS Text

Title: PLT OF EMS HELICOPTER HAD INTERFERENCE FROM HEART MONITOR DEVICE. TURNED VOLUME OF TWR FREQ TOO LOW TO HEAR TWR.

Narrative: IN OUR EMS HELI WE HAVE BEEN GETTING INTERFERENCE ON 130.0 (VHF AM), WHILE USING A PATIENT HEART MONITOR. THE INTERFERENCE HAS BEEN IN THE FORM OF AN APPROX 1000 CPS TONE RECEIVED OVER THE VHF RADIO(S) (WE HAVE 2 IN OUR HELI). DURING A SHORT FLT FROM A HOSPITAL JUST N OF XXX, TO OUR HOSPITAL 13 NM W, THE INTERFERING TONE WAS PRACTICALLY CONTINUOUS AND QUITE DISTRACTING TO PLT'S THINKING, AS WELL TO HIS RECEPTION OF TWR XMISSION. JUST AFTER TKOF I CONTACTED XXX TWR, RECEIVED INSTRUCTIONS TO SQUAWK XXXX AND CLRNC TO DEPART THE TCA AT OR BELOW 2400', WHICH I ACKNOWLEDGED AND COMPLIED WITH. NOW, HOWEVER, THE INTERFERENCE WAS SO LOUD ON TWR FREQS (135.0 AND 120.0 [ZZZ]) THAT I INADVERTENTLY TURNED MY TWR VOL CTL SO LOW THAT I COULD NOT HEAR XXX TWR AT ALL. MY ATTN, SINCE WE WERE ALREADY W OF XXX TFC, WAS DIRECTED AT TFC APCHING ZZZ FROM THE NE (XING FROM RIGHT TO LEFT, AHEAD OF ME). AS I WAS ENTERING ZZZ'S CTL ZONE 5 NM ENE, I TOLD XXX TWR I WAS GOING TO CHANGE TO ZZZ TWR, SINCE I HAD TFC IN SIGHT ON THE APCH TO ZZZ 23L. HEARING NO RESPONSE, I SHIFTED TO ZZZ, TOLD TWR I HAD TFC IN SIGHT. HEARING NO RESPONSE, I GLANCED AT VHF CTL, TURNED UP VOL AND CALLED AGAIN. THEY HAD HEARD FIRST CALL AND TOLD ME THAT OUR RADIO INTERFERENCE WAS NOT GOING OUT OVER THE AIR. SINCE INCIDENT I AM WORKING WITH MFR TO SEE HOW WE CAN ELIMINATE THE PROB OF NOISE INTERFERENCE.

Data retrieved from NASA's ASRS site as of July 2007 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.