Wesley brown Posted March 17, 2015 Report Posted March 17, 2015 Has anyone had their plane produce a wave or noise from the cockpit that when both radios are receiving a transmission it gets choppy and barely readable? I thought I would use my backup handheld and it sounded exactly the same! How could this be? We traced all the light and powered them off one by one. Checked the alt filter and found it to be broken and a new one didn't change a thing? This plane has a avionics hub and I hope it's not that because tracking that down would be tough. People say my transmission is crystal clear and air traffic control hears me just fine. It's only when I am trying to hear them that there is a wavy pattern in the transmission that makes it seem broken and barely readable. Any help on tracking this gremlin would be appreciated ! Quote
Hank Posted March 17, 2015 Report Posted March 17, 2015 Do you hear it in your headset? Check the wiring where the headset plugs in. Is it in your (left side) headset, or in both? That could be a bad connection somewhere besides the jack. What radios and intercom do you have? Those could make a difference, too. I hear a beep every time the LED on the belly flashes. It is much reduced in volume from the old Whelen high voltage flasher. Quote
Piloto Posted March 17, 2015 Report Posted March 17, 2015 Since you could hear it in your handheld have you tried turning off your cell phone, magneto, alternator field or another possible source. José Quote
Awqward Posted March 17, 2015 Report Posted March 17, 2015 Dumb question, but do you have an iPad charger plugged into the cigarette lighter socket? Quote
Bob - S50 Posted March 17, 2015 Report Posted March 17, 2015 Were both radios tuned to frequencies that were only slightly different? For example 121.5 and 121.4?  Bob Quote
Rhumbline Posted March 17, 2015 Report Posted March 17, 2015 I had a similar problem. With the engine running and changing rpm and selecting individual magnetos it was confirmed that the source of the trouble was ignition noise. The mags were due for overhaul anyway and I replaced the ignition harness (unquestionably original) at the same time and reception on both radios is now clear as a bell. 1 Quote
Yetti Posted March 17, 2015 Report Posted March 17, 2015 learned something this weekend that the p leads need to shielded. The shield at the ferrule will become un soldered.  Some people will do a work around and run another ground wire from the shield to another screw. 1 Quote
Wesley brown Posted March 19, 2015 Author Report Posted March 19, 2015 Since you could hear it in your handheld have you tried turning off your cell phone, magneto, alternator field or another possible source.José I hadn't timed off my cell phone I'll try that. I have cycled both mags and it's still there. I can't cycle the alternator because I can't pull the breaker but I did just put a brand new filter on the alternator. The beacon was constantly on and we cut the wire to disconnect it and see if that was the culprit? It didn't help. It funny my radio master switch kills all the power on my plane even the lights . Next flight I will kill the panel power and see if I still get the noise with just the engine running. Quote
Wesley brown Posted March 19, 2015 Author Report Posted March 19, 2015 Dumb question, but do you have an iPad charger plugged into the cigarette lighter socket? I never had the charger or anything else plugged in to the lighter socket. I did run a GPS module on the dash but had it off on the last flight still no luck. Quote
Wesley brown Posted March 19, 2015 Author Report Posted March 19, 2015 Were both radios tuned to frequencies that were only slightly different? For example 121.5 and 121.4?  Bob I had them tuned differently and also the same. I've switched them off independently and cycled the audio panel on different radios. Quote
Wesley brown Posted March 19, 2015 Author Report Posted March 19, 2015 I had a similar problem. With the engine running and changing rpm and selecting individual magnetos it was confirmed that the source of the trouble was ignition noise. The mags were due for overhaul anyway and I replaced the ignition harness (unquestionably original) at the same time and reception on both radios is now clear as a bell. This sounds reasonable. My harness wires are fairly new but I had seen a wire that was worn and torn through. In one spot. I tried to put some tv on there to shield it. Today I will fly the plan end tuen the whole panel off to se if my handheld will still pick it up. I have cycled the mags and it didn't make any change? It could be potosi able that both mags harnesses have shielding issues. Quote
Wesley brown Posted March 19, 2015 Author Report Posted March 19, 2015 learned something this weekend that the p leads need to shielded. The shield at the ferrule will become un soldered.  Some people will do a work around and run another ground wire from the shield to another screw. I knew that the p leads were shielded but never knew why. This makes perfect sense! I will check this as well and hopefully find the culprit coming from the engine as it is much easier to troubleshoot than electronics and avionics hub! Thanks for the info guys this really helps me try to think about the whole picture on finding the issue! Quote
Wesley brown Posted March 20, 2015 Author Report Posted March 20, 2015 I checked that the shields on the p mags were ground properly today and also changed the alternator noise filter . I started the plane and did some ground check using my handled zip tied transmitting my cars radio for reception. This problem still existed as I ran the plane about 20 total minuets over three times. I was using another handheld inside the plane trying to hone in on the noise! Finally on the last test everything just cleared up and I started hearing the reception crystal clear. I test flew the plane and the radios were working perfect! I have no idea what happened I'm just glad it's fixed and the noise went away. Let's hope it stays that way! Quote
Yetti Posted March 20, 2015 Report Posted March 20, 2015 Water in the reverbulating framulator 1 Quote
mike20papa Posted March 20, 2015 Report Posted March 20, 2015 Wesley, Could also be the shielding on the strobe power wiring, maybe? Make sure the ground strap from the engine to the firewall is good, clean & tight connection. If it comes back, try powering up your avionics without the engine running, or did you do that? Quote
Wesley brown Posted March 20, 2015 Author Report Posted March 20, 2015 Yes we did power up and power down almost everything with engine running and off. We could never isolate the noise I even cut the lined to the beacon because it could not be turned off. I think it was weird that when the engine was off no noise. But when it was on you could cycle the mags and no change. The alt couldn't be turned off to check it but a new filter didn't change anything. Nor was it rpm generated? I thinking that my com1 GPS antenna was the culprit! I had my hand hel and I could pick up a slight noise whet the antenna sweeping by it. When I went past it the noise cleared up. This was installed so the previous owner could have a gps antenna for his hand held gps. The antenna is very weak and the radio is putting out 10 watts to the coax but will barely transmit 10 miles out. Do antennas need to be grounded??? Quote
Wesley brown Posted April 12, 2015 Author Report Posted April 12, 2015 Update! And advise needed. ThE noise is being generated from the engine. We tried everything. Remember we can pick this up on a hand held as well and it's clear on transmission just noisy on reception. It's a pop pop pop sound and when receiving a transmission you can shut the engine down and herea the pop---pop-------pop---------------------pop until the blade stops with mags on and leaning out. So we 1. Disconnected the field wire from the alternator. No change 2. Disconnected the starter and ran it. No change 3. Disconnected p leads and ran it. No change 4. Each mag sounds the same . We ran them individually and no change. Only when it stops. 5. So we thought harness was bad. Pulled the plane I the hanger and ran the engine in the dark trying to find a arc. NOTHING 6. We figured maybe a plug could be transmitting somehow and go to looking and the plane has two rem38 plugs and the rest is rem40????. 7. Brand new filter on alternator. 8. Cleaned existing grounds and added more grounds. This helped my CHT gauges and starter! I have added some grounds and I know it's coming from the mags but how? It's not p leads! There shielded and I ran a good ground to them so I'm thinking maybe plug wires? The mags are grounded or they wouldn't shut off or cycle . There not hot! Keep in mind my friends are engineers one is from Boeing! Who is one of my IA's they share stumped! The only thing I haven't done is remove the belt from the alternator. Quote
Awqward Posted April 12, 2015 Report Posted April 12, 2015 Did you try running it without the alternator belt - or at least loosened off so it doesn't drive the alternator...just me clutching at straws! Anthony Quick Quote
Guest Posted April 12, 2015 Report Posted April 12, 2015 Update! And advise needed. ThE noise is being generated from the engine. We tried everything. Remember we can pick this up on a hand held as well and it's clear on transmission just noisy on reception. It's a pop pop pop sound and when receiving a transmission you can shut the engine down and herea the pop---pop-------pop---------------------pop until the blade stops with mags on and leaning out. So we 1. Disconnected the field wire from the alternator. No change 2. Disconnected the starter and ran it. No change 3. Disconnected p leads and ran it. No change 4. Each mag sounds the same . We ran them individually and no change. Only when it stops. 5. So we thought harness was bad. Pulled the plane I the hanger and ran the engine in the dark trying to find a arc. NOTHING 6. We figured maybe a plug could be transmitting somehow and go to looking and the plane has two rem38 plugs and the rest is rem40????. 7. Brand new filter on alternator. 8. Cleaned existing grounds and added more grounds. This helped my CHT gauges and starter! I have added some grounds and I know it's coming from the mags but how? It's not p leads! There shielded and I ran a good ground to them so I'm thinking maybe plug wires? The mags are grounded or they wouldn't shut off or cycle . There not hot! Keep in mind my friends are engineers one is from Boeing! Who is one of my IA's they share stumped! The only thing I haven't done is remove the belt from the alternator. There should be a way of disabling the alternator field, be either a switch or a circuit breaker. If not you can disable the alternator by pulling the field wire off the field stud on the alternator, easier than removing the belt. Clarence Quote
Wesley brown Posted April 12, 2015 Author Report Posted April 12, 2015 We did take the field wire off the regulator to isolate the alternator. I think it is the mag harness wires! Quote
Wesley brown Posted April 17, 2015 Author Report Posted April 17, 2015 Guess what it was! It was the mag harness wires. I changed them and the radios are crystal clear. Quote
Rhumbline Posted April 17, 2015 Report Posted April 17, 2015 Guess what it was! It was the mag harness wires. I changed them and the radios are crystal clear. Told ya! Quote
Wesley brown Posted April 17, 2015 Author Report Posted April 17, 2015 Yeah I tell you, I didn't know a Set of wires could look perfectly fine but be crap and cause so Mutch trouble. Well now I have new plugs and wires. Quote
Rhumbline Posted April 17, 2015 Report Posted April 17, 2015 Yeah I tell you I didn't know. Set of wires could look perfectly fine but be crap and cause so Mitch trouble. Well now I have new plugs and wires. Â Glad you're back in business! Â Quote
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