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Thread: Icom A200 Antenna Cable and intercom grounds

  1. #1
    CamTom12's Avatar
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    Icom A200 Antenna Cable and intercom grounds

    Replacing a bad RG58 antenna cable with RG400. The antenna side is a male BNC, but I can't figure out the radio side. It's an L-shaped connector that looks like a male BNC but doesn't have a 1/4-turn locking collar. Can I use a regular male BNC there? Can you remove the locking collar on a male BNC?

    While I'm in there, I'm adding the rear two seats to my intercom. Any tips for avoiding EMI noise on the intercom?

    Thanks for any help, I'm trying to order parts tonight so I can get the plane back together before the weekend.

    EDIT: this looks like what I currently have on there:



    Last edited by CamTom12; 07-16-2019 at 12:10 AM.

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    Gordon Misch's Avatar
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    looks like a male BNC but doesn't have a 1/4-turn locking collar
    Any chance it could be an RCA plug?
    Edit: Given your pic, nope. Sorry!
    Last edited by Gordon Misch; 07-16-2019 at 12:13 AM.
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    wireweinie's Avatar
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    Use a DBA 600 connector for the coax instead of the one in your picture. No soldering and a standard BNC male connector mates directly to it.

    Can you tell us what model intercom you are using? There are a couple of wiring styles that are used to connect jacks, depending on the brand/model. Either way uses shielded wiring. Also, be sure to use isolation washers to insulate the jacks from airframe ground.

    Web
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    CamTom12's Avatar
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    Thanks Web! Iíll order up the RG400 with BNCís and that adapter tonight!

    Intercom is a PS Engineering 1000 ii


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    wireweinie's Avatar
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    You'll need some 24 gauge, two conductor, shielded wire for the audio and mic jacks. For the headphones, one conductor will go to audio hi and the other to audio lo. For the mic, one conductor goes to mic hi and the other goes to mic lo. No push to talk function at the rear stations. The shields for all wires need to be tied to airframe ground at one end only. Use Sumitomo L-C-3 solder sleeves to attach a pigtail wire to each shield for grounds. Use Switchcraft 1028 and 1029 isolation washers on each jack.

    If you can send me a pic of the harness plug on from the back of the intercom box, I can tell you what pins or sockets to use to install the audio and mic wires.

    Web
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  6. #6
    CamTom12's Avatar
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    For the intercom work, I currently have 30í 22ga shielded 3 conductor wire (need 24í as measured tonight), single strand 22ga wire (bond), 2 each mono headphone and mic jacks, 2 soldering sleeves, and 2 sets of insulated shoulder and flat washers.

  7. #7
    CamTom12's Avatar
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    Icom A200 Antenna Cable and intercom grounds

    Quote Originally Posted by wireweinie View Post
    If you can send me a pic of the harness plug on from the back of the intercom box, I can tell you what pins or sockets to use to install the audio and mic wires.

    Web
    I only thought to get a pic of the connector side:



    This is as-installed with only pilot and copilot phone and mic, pilot-only PTT.

    I can get a pic of the intercom box side of the connector tomorrow if that helps.

  8. #8
    wireweinie's Avatar
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    3 conductor will work but you'll have one conductor not used on each run.

    Web
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    wireweinie's Avatar
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    Quote Originally Posted by CamTom12 View Post
    I only thought to get a pic of the connector side:



    This is as-installed with only pilot and copilot phone and mic, pilot-only PTT.

    I can get a pic of the intercom box side of the connector tomorrow if that helps.
    Use 205089-1 pins to crimp onto the wires. Do you have a diagram for the wiring?

    Web
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    CamTom12's Avatar
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    Quote Originally Posted by wireweinie View Post
    You'll need some 24 gauge, two conductor, shielded wire for the audio and mic jacks. For the headphones, one conductor will go to audio hi and the other to audio lo. For the mic, one conductor goes to mic hi and the other goes to mic lo. No push to talk function at the rear stations. The shields for all wires need to be tied to airframe ground at one end only. Use Sumitomo L-C-3 solder sleeves to attach a pigtail wire to each shield for grounds. Use Switchcraft 1028 and 1029 isolation washers on each jack.
    Quote Originally Posted by CamTom12 View Post
    For the intercom work, I currently have 30í 22ga shielded 3 conductor wire (need 24í as measured tonight), single strand 22ga wire (bond), 2 each mono headphone and mic jacks, 2 soldering sleeves, and 2 sets of insulated shoulder and flat washers.
    Well, shoot. I ordered the three conductor stuff about 2 years ago after watching a video on YouTube of some jacks being wired up that way. I probably should have asked here first! Iíll order some 2 conductor wire tonight as well.

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    CamTom12's Avatar
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    Quote Originally Posted by wireweinie View Post
    3 conductor will work but you'll have one conductor not used on each run.

    Web
    Iíll actually need 48í to wire it up the way you said. Iíll get the right stuff this time.

    Thanks for the help!

  12. #12
    wireweinie's Avatar
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    Also, you'll need the specific part number on the intercom box in order to get the correct wiring diagram. I'm guessing either 11920 or 11922.

    Web
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    CamTom12's Avatar
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    Quote Originally Posted by wireweinie View Post
    Use 205089-1 pins to crimp onto the wires. Do you have a diagram for the wiring?

    Web
    I just double-checked my logs, no wiring diagram. I found one on-line but the pins donít seem to match my connector, specifically pins 19 and 6 for the copilot.

    Page 9 here: http://www.ps-engineering.com/docs/P...l%20Manual.pdf

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    CamTom12's Avatar
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    Quote Originally Posted by wireweinie View Post
    Also, you'll need the specific part number on the intercom box in order to get the correct wiring diagram. I'm guessing either 11920 or 11922.

    Web
    Iím guessing 11922 based on no ďcrewĒ option, but didnít snag a photo of the backside of the box to verify.

  15. #15
    wireweinie's Avatar
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    Need that part number to be sure. The audio wires differently for each number.

    Web
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    CamTom12's Avatar
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    Quote Originally Posted by wireweinie View Post
    Need that part number to be sure. The audio wires differently for each number.

    Web



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    wireweinie's Avatar
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    rear seat wiring

    Click image for larger version. 

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    Here is a screen shot from the wiring diagram for PM1000ii, part number 11922. See that the audio for both rear stations is paralleled to the copilots audio. I like running the right audio off the copilots audio jack, just like the diagram shows. But I've found that it's easier to run the left rear audio by soldering the audio wires to the copilots audio, right inside the backshell of the connector plug. Run the rear mic lines (pins 8 and 9) just like the diagram shows. I.e. the mic lo wire is soldered along with the pigtail wire under the solder sleeve. A little work now, but if it's done right, you'll never touch it again until it's time for an update.

    Web
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    CamTom12's Avatar
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    Quote Originally Posted by wireweinie View Post
    Click image for larger version. 

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    Here is a screen shot from the wiring diagram for PM1000ii, part number 11922. See that the audio for both rear stations is paralleled to the copilots audio. I like running the right audio off the copilots audio jack, just like the diagram shows. But I've found that it's easier to run the left rear audio by soldering the audio wires to the copilots audio, right inside the backshell of the connector plug. Run the rear mic lines (pins 8 and 9) just like the diagram shows. I.e. the mic lo wire is soldered along with the pigtail wire under the solder sleeve. A little work now, but if it's done right, you'll never touch it again until it's time for an update.

    Web
    Thanks, Web!

    One more question: since Iím going to go ahead and completely rewire the intercom, how does my PTT connect to the A200?

    Hereís the radio wiring diagram:



    I *think* that Iíll run pins H and 7 from the A200 to pins 17 and 4 on the intercom. And pins J and 8 from the A200 to pins 25 and 13 on the intercom.

    I think Iíll need to use a momentary switch to ground pin 9 on the A200 with pin 12 on the intercom for PTT, but do I do that through pin 24 on the intercom?

  19. #19
    wireweinie's Avatar
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    Wire the pilot's and copilots PTT switch as per the PM1000ii diagram. Basically this switch will short the PTT line to audio lo at the jack. When this happens the intercom will tell the radio that it's time to transmit. To make this happen the following wires need to be connected at the emergency mic jack; pin 12 on the intercom connects to pin 9 from the radio at the ptt tab. Pin 25 from the intercom connects with pin J from the radio at the mic hi tab. Pin 13 from the intercom connects with pin 8 from the radio at the mic lo tab.

    Web
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    CamTom12's Avatar
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    Web, I appreciate the help - thanks again!

    I made a wiring diagram specific to my install. Looks a lot like the factory diagrams but I think it helped me keep the pins and wire runs straight in my head.

    Supplies come in tomorrow, Iíll report back when done!


  21. #21
    wireweinie's Avatar
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    That should work.

    See the phones line that runs over the cabin from right rear to left rear? That's the run that I solder to the copilots audio lines inside the backshell of the intercom connector. That will allow you to run the phone and mic lines together down the left and right sides without making the cross over in the cabin roof. Just simplifies the runs.

    Let us know how the project turns out.

    Web
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  22. #22
    CamTom12's Avatar
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    Icom A200 Antenna Cable and intercom grounds

    Quote Originally Posted by wireweinie View Post
    That should work.

    See the phones line that runs over the cabin from right rear to left rear? That's the run that I solder to the copilots audio lines inside the backshell of the intercom connector. That will allow you to run the phone and mic lines together down the left and right sides without making the cross over in the cabin roof. Just simplifies the runs.

    Let us know how the project turns out.

    Web
    Ah, I gotcha. Makes sense, Iíll run it that way.

    EDIT: updated my diagram for the better LR Phone wire run.

    Last edited by CamTom12; 07-17-2019 at 01:03 PM.

  23. #23
    CamTom12's Avatar
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    Well, I got it all wired up and messed up a little. I put all my bonding/connections too close to the pins and I can't get the D-sub backshell back on. I left a small service loop, so I'm going to order some more solder sleeves and pins and try terminating those again, but further away from the backshell. I think I'll get some larger heatshrink to cover those connections in a bigger bundle and make it look nice when I'm done.

    I shot the wires in the connector to make sure I wouldn't let the magic smoke out of the box, then I went ahead and plugged it all up (minus the backshell) to see if there was a difference. A couple of observations:

    1) Holy cow! Its quiet now, I can't hear my strobes or wig-wags anymore!

    2) I can still hear when my usb adaptor is plugged in and charging something. I'm going to rewire the cigar lighter with shielded wiring and move the ground to my main airframe cluster to see if that helps.

    3) When I have music playing, the PS Engineering "soft mute" feature works with the VOX, but doesn't work when the radio receives. I tuned up ATIS and can hear the radio just fine in the headphones, but the music doesn't mute. The music used to mute with VOX or radio, so I'm not sure what I did wrong here. I'm going to do some searching tonight. If I had a choice, I'd actually run it the other way around - mute with the radio but not with the intercom. I'm not sure if there are any user-configurable settings though.

    EDIT:
    I just read the correct operator's manual for my intercom (step one, right?) and it says:
    The entertainment mute trip level determines what volume the aircraft radiomust be before the music mutes. This is factory adjusted. If your entertainment does not mute, try increasing the volume of the aircraft radios.
    I didn't try messing with the radio volume, I'll try that tomorrow.
    Last edited by CamTom12; 07-21-2019 at 02:19 AM.
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    Icom A200 Antenna Cable and intercom grounds

    Quote Originally Posted by CamTom12 View Post
    3) When I have music playing, the PS Engineering "soft mute" feature works with the VOX, but doesn't work when the radio receives. I tuned up ATIS and can hear the radio just fine in the headphones, but the music doesn't mute. The music used to mute with VOX or radio, so I'm not sure what I did wrong here. I'm going to do some searching tonight. If I had a choice, I'd actually run it the other way around - mute with the radio but not with the intercom. I'm not sure if there are any user-configurable settings though.

    EDIT:
    I just read the correct operator's manual for my intercom (step one, right?) and it says:

    The entertainment mute trip level determines what volume the aircraft radiomust be before the music mutes. This is factory adjusted. If your entertainment does not mute, try increasing the volume of the aircraft radios.
    I didn't try messing with the radio volume, I'll try that tomorrow.
    I turned up the radio volume and the soft mute works fine. Now just wait for more supplies to try terminating again.
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    CamTom12's Avatar
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    Well, the supplies came in and I got the job done! I really wish that I hadnít had to do part of it again, but Iím glad itís done the right way now.

    Hereís a strange thing: when I put the new antenna cable in, I tested it with some LED navigation lightbulbs that I had in the plane a while back. I had taken those LED bulbs out because I was getting a lot of radio noise whenever the NAV lights were on. I was hoping that the new antenna cable would fix that but it didnít. It actually sounded the same as it did with the old cable. I ran a temporary ground from the antenna back to my main airframe ground to see if that was this issue and it was not.

    The radio is grounded near where the intercom is.

    Any ideas?

    Thanks!

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    wireweinie's Avatar
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    Is the noise coming in on the radio or on the intercom? Check by turning off the radio and seeing if the noise stays or goes. Do the same with the intercom. Are your nav lights grounded out at the light? Are the nav/strobe power wires routed near the audio and mic lines? Did you route the antenna coax with the nav power lines? You can turn on the nav lights and unplug the bulbs one at a time until the noise stops. That should tell you which bulb is the source.

    Web
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    www.SkupTech.com mike mcs repair's Avatar
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    are you using the airframe as the ground path for the lights?

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    Quote Originally Posted by wireweinie View Post
    Is the noise coming in on the radio or on the intercom? Check by turning off the radio and seeing if the noise stays or goes. Do the same with the intercom. Are your nav lights grounded out at the light? Are the nav/strobe power wires routed near the audio and mic lines? Did you route the antenna coax with the nav power lines? You can turn on the nav lights and unplug the bulbs one at a time until the noise stops. That should tell you which bulb is the source.

    Web
    It's coming from the radio. It sounds like white noise in the background when I'm receiving a transmission, and my receive strength (well, volume) appears weaker when the nav lights are on. No impact to the intercom. I actually have two sets of very similar LED position bulbs, and one bulb is much louder than the others. However, I noticed last night the noise and volume reduction even with incandescent bulbs in the wingtips (an LED in the tail), although the noise and signal reduction was barely perceptible. If I hadn't known to listen for it I might not have noticed. With the good set of LEDs it's apparent but not unreadable. With the bad set of LEDs my local airfield's ATIS wouldn't break squelch from in the hangar. I didn't think to try swapping or pulling the tail bulb at the time.

    I used shielded wires in between the radio and intercom, and the only other wires in the radio connector are power, ground and their associated jumpers.

    All the wires go up the "A-pillar" in front of the door in a bundle, but otherwise are pretty separated. My antenna is a Comant on the right side wing root fairing.

    Quote Originally Posted by mike mcs repair View Post
    are you using the airframe as the ground path for the lights?
    I'll have to pull the nav light housing out to verify, but everything else that could be grounded through it's mounting location has been grounded that way. As I take on electrical projects under the panel, I've been adding grounds back to a cluster behind the dash as I go. There's still quite a bit that are locally grounded though.

  29. #29
    wireweinie's Avatar
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    Forget the LED bulbs and just go with LED units. Or take a shot at a new set of LED bulbs to see if they are quiet.

    Shielding helps but does not stop noise, so make sure that your power wires are not bundled with ANY audio or mic wires (jack wiring also). Even in places like the windshield post, it helps to bundle power wires together and audio/mic wires together but not to each other. Never bundle a coax with any other wire.

    A good way to minimize noise issues with power wires, like at the navs, is to use shielded wire and run power through the center conductor and the ground through the shielding. That way the ground can be brought out of the wing and attached to the fuselage or even under the panel.

    Web
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    www.SkupTech.com mike mcs repair's Avatar
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    Simple to find out if itís the airframe ground being used by light, just run a temporary ground back to cluster and isolate from airframe at light. Does noise go away?


    Sent from my iPhone using SuperCub.Org

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    CamTom12's Avatar
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    Iíll try pulling a temporary ground from the lights.

    Random question - would a crappy dimmer introduce noise into the radio?

    I replaced a dimmer that was super wonky. Lots of internal issues and barely functioned except at full bright. You could feel the internals grinding when you turned it

    I didnít materially change my music input at all during my wiring rework last night, but went to the hangar today to make sure it worked before a trip next week.

    I noticed that the noise I heard before on the music circuit (I had assumed through the cigar lighter) was gone. But I didnít process that until later this evening back home. I should have stuck the LEDs back in to see if they cleaned up as well.

  32. #32
    wireweinie's Avatar
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    Depends on the type of dimmer, but they can make noise.

    Side note: music jacks need isolation washers, also, just like audio and mic jacks.

    Web
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    CamTom12's Avatar
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    Quote Originally Posted by wireweinie View Post
    Depends on the type of dimmer, but they can make noise.

    Side note: music jacks need isolation washers, also, just like audio and mic jacks.

    Web
    I reused the existing music jack but changed the wires. This one doesnít seem to have a good way to isolate the ring, but Iíll order a new one and replace it later.

    On Sunday Iíll go give the led nav bulbs another shot just in case the old rheostat was passing noise into the airframe or something.

    I really appreciate all your help!

  34. #34
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    Quote Originally Posted by CamTom12 View Post
    On Sunday Iíll go give the led nav bulbs another shot just in case the old rheostat was passing noise into the airframe or something.

    I really appreciate all your help!
    Unfortunately I didnít get a chance last week but Iíll try again tomorrow!
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    CamTom12's Avatar
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    Quote Originally Posted by CamTom12 View Post
    Unfortunately I didn’t get a chance last week but I’ll try again tomorrow!
    Had limited time at the hangar so I prioritized my alternator over the LEDs. I'll give it a shot when we get back from vacation.

  36. #36
    CamTom12's Avatar
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    Today I swung by the hangar to get some measurements for another project and saw my neighbor was installing some G5's in his Cherokee. He's an EE for Boeing.

    I showed him my nav light set-up and asked what he thought about the radio noise I was getting with those LEDs (also plugged them back up and verified it was still there). He agreed it was weird I was getting radio noise but said an inductor in-line with the nav light power wire would get rid of the noise. He's going to drop off a couple extras he has tomorrow and I'll install them when I get back from vacation.

    I pulled the right wing nav light/strobe housing off, and the nav light has a single power wire and is grounded through the mounting screws. We shot the ground and it's good from the nav light housing screws to the battery ground (through the airframe). The strobe has a hot, ground, and signal (or sync?) all in a shielded wire. Right now that shielding's not bonded on either side, but I'm not getting any strobe noise in the radio or the ICS. I'm going to bond it though, more for general purpose than anything else.

    I have a sinking feeling this is going to end up with rewiring the nav light circuit under the dash, since that's connected to the panel lights and the dimmer and all that. Maybe something funky is going on under there and that's what's causing a change from incandescent to LED nav lights to drop my radio reception like crazy? Either way, not looking forward to more time upside-down under the dash.

  37. #37
    wireweinie's Avatar
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    Bad call with the inductors. It's a band aid over a noise issue. Fix the source of the noise as that is the actual problem.

    Have you pulled the bulbs to verify which one is making the noise? We're asking about the grounds as they can easily be a source of noise injected into the audio. Running a ground wire from the light to a ground point close to the battery will keep that current path separate from all others. THAT equals no noise. Until you figure out the exact source of the noise, any 'fixes' will be a shot in the dark, at best.

    Only connect one end of the shield to ground. Connecting both ends can set up a ground loop (squeal in headset).

    Web
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    CamTom12's Avatar
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    Quote Originally Posted by wireweinie View Post
    Bad call with the inductors. It's a band aid over a noise issue. Fix the source of the noise as that is the actual problem.
    I donít want a band-aid, Iíd rather fix it right if thereís a way to do that.

    Quote Originally Posted by wireweinie View Post
    Have you pulled the bulbs to verify which one is making the noise?
    Iíve got two sets of led position light bulbs, Iíve rotated them all through. One set has a bulb thatís worse than the others but the other set still effects radio reception.

    Quote Originally Posted by wireweinie View Post
    We're asking about the grounds as they can easily be a source of noise injected into the audio. Running a ground wire from the light to a ground point close to the battery will keep that current path separate from all others. THAT equals no noise.
    I havenít done this yet. Trying to figure out the best way to snake a new wire through the wing and secure it. Looks like the original wiring was run before the wings were covered.

    Quote Originally Posted by wireweinie View Post
    Until you figure out the exact source of the noise, any 'fixes' will be a shot in the dark, at best.
    Agreed. I have tried running a ground from my antenna ground path directly to the battery ground with no effect from the LED bulbs interference. Havenít done that from the bulb housing yet.

    Does this problem seem unique to my airplane or is this more of a common issue?

    Quote Originally Posted by wireweinie View Post
    Only connect one end of the shield to ground. Connecting both ends can set up a ground loop (squeal in headset).

    Web
    Will do. Thanks!

  39. #39
    wireweinie's Avatar
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    Have you tried a different brand of LED bulbs? When you pull the bulbs, one at a time, does the removal of one bulb stop the noise? If so, that bulb or that socket is the source of the noise. How about putting in the original bulbs? Not LED but no noise.

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    Life's tough . . . wear a cup.

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    Quote Originally Posted by wireweinie View Post
    Have you tried a different brand of LED bulbs? When you pull the bulbs, one at a time, does the removal of one bulb stop the noise? If so, that bulb or that socket is the source of the noise. How about putting in the original bulbs? Not LED but no noise.

    Web
    No, same brand but two different models of LED bulbs.

    Iím pretty sure I pulled them individually and saw the noise in both wings with the ďgoodĒ set of LEDs, but that was a couple of weeks ago and at 3am. Iíll run that test again this afternoon if I can get out of work a little early.

    Original, incandescent bulbs make no noise. With an LED (same brand) in the tail I have just the faintest amount of noise. Imperceptible with the engine running.

    The easy answer is to just slap the incandescent bulbs back in, which is what Iíve been doing. I was hoping the new antenna cable (which I would have replaced regardless) would have allowed these LEDs in the wings. Iíll keep trying to find and fix the noise source though, since I want it done right.

    I really appreciate yíallís help with troubleshooting tips and steps Iím missing!

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