Headset Feedback Squeal

AggieMike88

AggieMike88

Touchdown! Greaser!
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The original "I don't know it all" of aviation.
Aircraft: 1975 C182P
Headset: Lightspeed Zulu.2, straight cord/plug
Audio Panel: KM24

Need some troubleshooting help.

A few times recently, after I've started up at the hangars and approached the movement area line, I've gotten a loud feedback squeal when I engaged the PTT button on the yoke.

While on the taxiway, engine running, I've tried a few simple things such as removing and re-inserting the plugs, cycling the masters switch power, etc. But the squeal persists. What I haven't tried yet is fresh batteries.

Squeal only occurs when I press the PTT. Intercom operation and hearing normal radio traffic is fine.

Fortunately I had a spare headset in the aircraft. Switched to that one and no squeal and I continued the flight.

On the return flights, I switched back to the Zulu.2 that caused the squeal. All worked normally, and no squeal.

Besides fresh batteries, what else could I try?
 
One more thing that occassionally happens to me,

Audio panel is selected to BOTH com 1 and com 2. Then it feedsback through the com I'm not transmitting on, but its not really a squeel like your saying.
 
What kind of headset are you using? If I recall correctly, you recently acquired a QT Halo headset and, if I'm correct, I've experienced this exact issue as well.

In my plane, if I have the QT Halo headset on, and I select my No. two COM radio (a Narco Mark 12D), when I key up to transmit, I get a very loud squeal. It sounds like feedback, but it is not.

The manufacturer of the QT Halo graciously exchanged at the headset for another one, which he told me had a modification of some sort which would make this problem less likely to occur, but it made no difference.

Because my wife is the one who usually uses the Halo, and because I am preparing to replace my intercom and audio panel with a new PS engineering unit, my troubleshooting has stopped. But I would like to know what is causing this, and will likewise report back on what results after the Audio Panel/ Intercom replacement.
 
bnt83 said:
One more thing that occassionally happens to me,

Audio panel is selected to BOTH com 1 and com 2. Then it feedsback through the com I'm not transmitting on, but its not really a squeel like your saying.
Click to expand...

Ahah! It might be this. The KM24 permits both to be "on" but it's not an obvious indication like the Garmin panel.

And this might explain why later, there is no problem (I had switched off Comm2 after changing headsets).
 
AggieMike88 said:
Ahah! It might be this. The KM24 permits both to be "on" but it's not an obvious indication like the Garmin panel.

And this might explain why later, there is no problem (I had switched off Comm2 after changing headsets).
Click to expand...

Mine will do the same, but only from Com 1 to Com 3, Com 2 (GX-60) doesn't receive any feed back.
 
SCCutler said:
What kind of headset are you using? If I recall correctly, you recently acquired a QT Halo headset and, if I'm correct, I've experienced this exact issue as well.

In my plane, if I have the QT Halo headset on, and I select my No. two COM radio (a Narco Mark 12D), when I key up to transmit, I get a very loud squeal. It sounds like feedback, but it is not.
Click to expand...

Yes to purchasing the QT Halo, but the offending set is my Zulu.2's (but you might recall us getting a squeal or feedback with the Halo's in Dave's King Air copilot position. All other positions in Dave's plane functioned fine)

I think the culprit is having Comm1 and Comm2 audio circuits both live at the same time when I try to transmit.

The manufacturer of the QT Halo graciously exchanged at the headset for another one, which he told me had a modification of some sort which would make this problem less likely to occur, but it made no difference.

Because my wife is the one who usually uses the Halo, and because I am preparing to replace my intercom and audio panel with a new PS engineering unit, my troubleshooting has stopped. But I would like to know what is causing this, and will likewise report back on what results after the Audio Panel/ Intercom replacement.
Click to expand...

The headset I switched to for the ride out to Walt's last weekend (which is the last time I got the squeal) was the Halo. No squeal occurred on that set.
 
I've been fighting a very odd intercom squawk. My Lightspeed Sierras will not work in the copilot position, but my Zulu does. The Sierras work in the other seating positions.

When the failure is present, I can plug in a DRE or the Zulus into the copilot jacks and it works fine. :mad2:



While its not working, I can't hear anything in the sierras as I plug in the headphone plug then only after the mic is plugged in, can I barely hear anything. Then pull the plugs and insert them into a passenger seat set it works fine. :dunno:

Either there is something wrong with the Sierras or the PM3000 stero intercom, or it's wiring, is messed up.
 
It looks like you got the issue solved, tracking it to the intercom.

FYI, for everyone, there is another source for "squealing" or "screeching" in a headset. It's only with ANR headsets. You will get the sound when adjusting the headset on and off your head or pushing any powered control, i.e. the ANR power, PTT switch, etc. It's caused by the ANR mic's in the ear assemblies, and means the mics are asymmetrical in the assembly, and you've got the headset on backwards, there is a cold solder, the internal mic has shifted, or has come loose.
If you ever find yourself with this issue, and new batteries, flipping them around, or a second intercom test renders the same results you'll need to send them in.
 
Last edited:
Archammer said:
It looks like you got the issue solved, tracking it to the intercom.

FYI, for everyone, there is another source for "squealing" or "screeching" in a headset. It's only with ANR headsets. You will get the sound when adjusting the headset on and off your head or pushing any powered control, i.e. the ANR power, PTT switch, etc. It's caused by the ANR mic's in the ear assemblies, and means the mics are asymmetrical in the assembly, and you've got the headset on backwards, there is a cold solder, the internal mic has shifted, or has come loose.
If you ever find yourself with this issue, and new batteries, flipping them around, or a second intercom test renders the same results you'll need to send them in.
Click to expand...


I have an OLD DRE ANR set that does nothing but squeel no mater what I do.
 
bnt83 said:
I've been fighting a very odd intercom squawk. My Lightspeed Sierras will not work in the copilot position, but my Zulu does. The Sierras work in the other seating positions.

When the failure is present, I can plug in a DRE or the Zulus into the copilot jacks and it works fine. :mad2:



While its not working, I can't hear anything in the sierras as I plug in the headphone plug then only after the mic is plugged in, can I barely hear anything. Then pull the plugs and insert them into a passenger seat set it works fine. :dunno:

Either there is something wrong with the Sierras or the PM3000 stero intercom, or it's wiring, is messed up.
Click to expand...

I bet your mic bias voltage is not present or more likely, reversed in polarity at that jack. The Sierra needs the bias voltage to operate some of the electronics in the little control box. It's not isolated from the aircraft like the Zulus are.
 
"I think the culprit is having Comm1 and Comm2 audio circuits both live at the same time when I try to transmit."

I think you are right Mike. When both COMs are receive enabled only the one with selected MIC is muted during transmit. Allowing the un-muted radio to feedback your transmit audio.

I had a similar problem with ANR headsets when transmitting on HF com. Some ANR headsets have no shielding on the cable thus allowing HF RF to couple like an antenna and thus feedback. Switching to regular headsets solved the problem.

José
 
A bit more investigation is needed....

Armed with the ideas in this thread, I headed to the hangar after work with my Zulu.2 headset.

plugged in, flipped on the battery and master switch, let both radio's power on, tuned to a frequency that isn't used in the immediate area, and started button mashing.

Result: Couldn't get it to squeal.

Well, that was kinda the desired result, but I was hoping I could replicate the problem too. Even with both Comm1 and Comm2 engaged on the audio panel, and the PTT pushed, no squeal.

Then I noticed that the battery level light was red, not green, and the ANR wasn't really on.

So I'll try again tomorrow morning (cooler then too!) with fresh batteries.
 
denverpilot said:
I bet your mic bias voltage is not present or more likely, reversed in polarity at that jack. The Sierra needs the bias voltage to operate some of the electronics in the little control box. It's not isolated from the aircraft like the Zulus are.
Click to expand...

I have a few spare jacks. Should be easy to test with some wire and aligator clips.
 
I'm resurrecting this thread because I am having the same issue - a loud squeal when transmitting. I have a Bose A20 with a Garmin GTR200 COM coupled with a GMA 240 Audio Panel. The squeal is present when the engine is off and when the engine is running. It is more pronounced when the engine is off and at high rpms. (Not as much at idle)

I've completed the following with no luck:
  1. Conducted a wiring continuity check.

  2. Conducted an inspection of the wiring for the radio.

  3. Checked the shielding that is around the cable for the radio, no nicks, cuts or damage to it.

  4. Checked the connections and made sure they are tight at all the connection points.
Any other suggestions?
 
Had a similar problem, someone suggested a ferrite core around the microphone cable:

http://www.aircraftspruce.com/catalog/pspages/icoma6a24.php

Seems to help, but I do occasionally get the squeal.

Another suggestion was to reduce the intercom volume and increase the headset volume. Something that helped for me was to reduce the sidetone volume level.

Ron Wanttaja
 
Quick update... I downloaded the Installation Manual for the GTR 200 today. Section 3.6 discusses the Post Installation Configuration and Checkout Procedure. I followed it step by step and found out that the COM SETUP was not completed properly. The MIC GAIN was supposed to be set at 5. Mine was set at 10. Once the adjustment was made, the squeal went away. Problem solved!
 
Hey all. Having a similar issue as described above. Vans RV12 with a GTR200 and G3X display. Recently the radio has developed a loud squeal and feedback noise when transmitting. It is somewhat random, doesn't do it every single transmission. Mic gain and side tone settings have been changed which helps reduce the issue, but by no means cures it. In fact they initially helped, but the problem seems to gotten worse. I've noticed it does it more frequently on lower frequencies. For example, I was enroute to KLVK and initially transmitting decently on 118.1. As I got closer to the airport, the squeal became louder. After I landed and was coping instructions to exit the runway, it squealed so bad I couldn't get a word in. I exited the runway and stopped. I switched to ground 121.6 and transmitted clear as day, no squeal whatsoever. I shut down, picked up a friend, transmitted on ground 5x5 back to the runway, switched to tower for takeoff and was barely able to get in a transmission to take off. Returned to drop off the friend, and experienced the exact same scenario. Luckily I had a backup handheld ready. All connections on the radio were pulled off, cleaned and inspected. No kinks or gouges in any of the insulation. The radio worked great for last two years. Any ideas?
 
I am having the same issue with my Lightspeed Sierra in my RV-12 with the GTR 200 and Skyview system.
 
Pinging this thread to see if anyone defintivly solved the problem. Seems to be two common pieces of data here. RV12 and the GTR 200. Mine GTR 200 recently developed this problem in the RV12.
 
I'm not sure what fixed it since my original post 6 years ago, but the airplane has had the PTT buttons replaced a time or two, the audio panel upgraded, the bayonet plug wiring upgraded, and some other avionics work done. And I'm flying with a Lightspeed PFX headset.

No squeals.
 
Flocker said:
I'm resurrecting this thread because I am having the same issue - a loud squeal when transmitting. I have a Bose A20 with a Garmin GTR200 COM coupled with a GMA 240 Audio Panel. The squeal is present when the engine is off and when the engine is running. It is more pronounced when the engine is off and at high rpms. (Not as much at idle)
Click to expand...

About that GTR 200. I have had a similar problem. And it turned out to be the radio. On certain Frequencies I would get a loud feedback squeal. It could also be heard by the tower. If I switched back to ground, the radio would be normal. No squeal. So I contacted Garmin and they exchanged out radio with another for $200. Problem solved. The side tone on the replacement radio is clearer, and has a better tone. The problem was in the GTR 200 not the headset.
Hope this helps you out.
ARt
 
I know this post is very old, but someone may come across it and I have the solution. I had been having the same issue on 2 of my Vans RV-12's. The Squeal was intermittent so it was hard to nail down. The issue was the GTR 200 mount. The back of it has two metal tabs with slots. The slots started to become larger over time which cause the back of the mount where the cable plugs into to become loose. From what it looks like the cable would move a bit and would cause the squeal. As the plane flew it would vibrate back into place. A quick fix was for us to to put a couple of small shims in the tab holes. This fixed the issue and it has not come back since. I hope this helps anyone who is experiencing this issue still.
 
Can I add to this question. Have Bose A20 with lemo plugs. For first time today I had the loud squeal when transmitting. Receive was fine. Switched to the copilot side with lemo and same thing. Had problem with 750 and backup KX155
Then I plugged a non ANR headset into the old dual plugs and it works fine. No squeal. Works fine on both sides.
Recent work was done. P lead had to be replaced from mag to switch. Didn’t make the noise before this. Maybe coincidental. Thanks for any suggestions
 
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