Narco Mark 12-D - Open Mic Sound

[Skates97]

I have old stuff in my plane, but for the most part it seems to work well. The Nav/Com is a Narco Mark 12-D and most of the time is great. However from time to time it seems to get "stuck" like it is receiving a transmission. I can still make a call they can hear me just fine and as soon as I release the push to talk button the static is back. If a radio call comes in it is clear and as soon as it is over the static is back. I can switch the audio panel to Nav 2 and it's fine but when I go back to Nav 1 the static is still there. Eventually after a few minutes it's gone and everything is back to normal. It sounds to me like possibly a loose connector, but before I went poking around I thought I would see if anyone had any ideas.

[Marauder]

I have old stuff in my plane, but for the most part it seems to work well. The Nav/Com is a Narco Mark 12-D and most of the time is great. However from time to time it seems to get "stuck" like it is receiving a transmission. I can still make a call they can hear me just fine and as soon as I release the push to talk button the static is back. If a radio call comes in it is clear and as soon as it is over the static is back. I can switch the audio panel to Nav 2 and it's fine but when I go back to Nav 1 the static is still there. Eventually after a few minutes it's gone and everything is back to normal. It sounds to me like possibly a loose connector, but before I went poking around I thought I would see if anyone had any ideas.

I had problems with the tray on my Mark 12D+. The latching mechanism on the Narco isn't the greatest.

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[thinwing]

Are you talking about the squelch setting/ circuit...?

[Piloto]

Sounds like a squelch setting problem. Either the squelch got too sensitive for weak signals or there is something in the plane causing the static.

José

[thinwing]

Been too long ,can't recall if old narco had a manual squelch

[thinwing]

Oh..just a thought do you have an IPhone or iPad charger in plane?

[thinwing]

If so unplug and see if noise goes away

[Skates97]

17 minutes ago, thinwing said:

Been too long ,can't recall if old narco had a manual squelch

I don't think it has a manual squelch, or if it does I have no idea what I am looking for (a real possibility).

15 minutes ago, thinwing said:

Oh..just a thought do you have an IPhone or iPad charger in plane?

No charger in the plane. The static will go away on its own without any changes to anything else and I can sometimes fly for an hour without a problem and sometimes it's only 10-15 minutes before it pops up for a few minutes.

[takair]

The volume knob, pull test, is the squelch.  Make sure it is in.  Play with it when you have the issue and see if it goes away.  As I recall, there are adjustments through the top of the case.  Also, try isolating by shutting off things like the alternator, to be sure a piece of failing equipment isn't causing it.  If you have a cheap cigarette lighter USB adaptor, try unplugging it, they are notorious.  I recently had one cause problems, as did a friend.

[N201MKTurbo]

Just push the volume knob in.

[Skates97]

Thanks, I'll give it a try next time I'm flying and it decides to act up.

Nothing in the cigarette lighter but if I decide to use a USB adapter sometime in the future I'll be sure to check that if I have interference problems pop up.

[thinwing]

Yep I thinks that's it...pull out push in...couple times

[carusoam]

As far as old radios go...  the Narco D stands for digital?  

The older Narco radio's squelch was a pull the knob, rotate it, put it back in routine.  It was always on the edge of having a lot of back ground noise.

It was also very sensitive to anything else in the plane.  You could hear a cell phone call coming in before the phone would show anything.  The sound of the electric motor for the anticollision light was loud.  The whiny sound sound of things charging is pretty interesting.

It may be related to all the ground wires not being attached as well as they can be.

Best regards,

-a-

Edited January 31, 2017 by carusoam

[Skates97]

Long enough flight last night to play around with it and see what I could do. The short answer is nothing.

I can pull the knob out and if I rotate it, it only controls the volume. In or out, it only adjusts the volume. I also tried pulling out/pushing in a few times and there was no change so I am thinking that the squelch doesn't work. I'm leaning towards a loose wire/connection, the kind of intermittent electrical problem that drives mechanics nuts at our dealerships. Parts of the flight the radio was perfect, then there would be a transmission and after the transmission ended there was static. Further incoming transmission would be crystal clear, followed by static when they ended and then after a period of time the static just cut out and it was quite like it's supposed to be. It may be something I have to live with for now.

[Smiles201]

I once had a similar problem and it turned out to be a loose wire connection at the back of the intercom. Could be something in the headphone or headphone jacks also. Use a different headset, a different jack station to isolate, move the wires around to see if that makes a difference.

[Skates97]

1 hour ago, Smiles201 said:

I once had a similar problem and it turned out to be a loose wire connection at the back of the intercom. Could be something in the headphone or headphone jacks also. Use a different headset, a different jack station to isolate, move the wires around to see if that makes a difference.

Thanks, I flew for an hour and a half yesterday and it never happened. It could very well be a loose connection somewhere. Nothing quite like chasing around an intermittent electrical problem.

[takair]

3 hours ago, Skates97 said:

Thanks, I flew for an hour and a half yesterday and it never happened. It could very well be a loose connection somewhere. Nothing quite like chasing around an intermittent electrical problem.

It is odd that the squelch did not work for you.  I use it every flight to set the volume.  Try 121.5 as well.  This frequency always has the squelch broken.  It actually makes it a pain to monitor guard with the squelch always broken.

[Marauder]

It is odd that the squelch did not work for you.  I use it every flight to set the volume.  Try 121.5 as well.  This frequency always has the squelch broken.  It actually makes it a pain to monitor guard with the squelch always broken.

Must be something in your neck of the Northeast. I monitor guard here all the time with IntelliAudio. If the squelch on 121.50 was open a lot, it would have driven me nuts. All I hear, other than the Guard Police is the periodic guy yelling "Guuuuuard".




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[takair]

It is unique to the MK12D. My Garmin behaves normally.

[Skates97]

Ok, a new piece of information that is causing me to lean towards the intercom. I have a Sigtronics SPA-400 in it. I was talking to my wife today about it and she mentioned that she has no idea how I can hear ATC or the radio calls when we are getting the static. Apparently on the right side, when I am getting the open squelch sound, there is static in the headset constantly, even when a transmission is coming in. She said she can barely hear the transmission because of the static. I told her that on the left side I get static when there is no transmission, but when I am receiving a transmission the static is gone and it is crystal clear. Because it is affecting both sides differently I am thinking it is perhaps the intercom, not the radio? Am I pointed in the right direction?

I did spray some electrical cleaner in the PTT switch and cycled it because sometimes when I am getting it if I click it then it will go away. Considering pulling the intercom and checking all the connections.

[Marauder]

Ok, a new piece of information that is causing me to lean towards the intercom. I have a Sigtronics SPA-400 in it. I was talking to my wife today about it and she mentioned that she has no idea how I can hear ATC or the radio calls when we are getting the static. Apparently on the right side, when I am getting the open squelch sound, there is static in the headset constantly, even when a transmission is coming in. She said she can barely hear the transmission because of the static. I told her that on the left side I get static when there is no transmission, but when I am receiving a transmission the static is gone and it is crystal clear. Because it is affecting both sides differently I am thinking it is perhaps the intercom, not the radio? Am I pointed in the right direction?
I did spray some electrical cleaner in the PTT switch and cycled it because sometimes when I am getting it if I click it then it will go away. Considering pulling the intercom and checking all the connections.

I would check the grounds on the intercom. I had an issue years ago with my Sigtronics and your symptoms sound vaguely familiar.


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[takair]

Try turning the intercom off to see if it changes the symptoms.  She may be hearing a different issue altogether.

[Andy95W]

Dumb question, but did you adjust the squelch and volume on the SPA-400, and then on the individual headsets?  You may have to readjust it in flight due to higher ambient noise levels.

Those intercoms are generally bulletproof.  Sigtronics will repair them readily if necessary. 

[Skates97]

39 minutes ago, Andy95W said:

Dumb question, but did you adjust the squelch and volume on the SPA-400, and then on the individual headsets?  You may have to readjust it in flight due to higher ambient noise levels.

Those intercoms are generally bulletproof.  Sigtronics will repair them readily if necessary. 

Not a dumb question, but my answer may be a dumb one... I have adjusted the squelch on the SPA-400, but on the individual headsets? Mine don't have any adjustment for squelch for the individual ones, or if they do I have no idea how. The only thing on the headsets themselves is just volume adjustment. I don't know of any squelch adjustment anywhere else besides the one on the Mark 12D but pulling the volume out (which someone said is the squelch) doesn't do anything. I'm going to check connections, given the completely intermittent nature of it. Flew 4 hours straight without it ever happening, and then had it happen constantly off and on for a couple of hours.

[Andy95W]

Sorry, Rich, I should have specified only volume on the headsets.

I'm thinking if pulling the squelch knob doesn't do anything, then it is probably malfunctioning and is now always on.  

Do you have a second radio, and does it happen to that one?  Or, if you actually turn the radio off, does the problem go away?  I think if you keep working on isolating the problem you will find it.