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Icom A200 Antenna Cable and intercom grounds

CamTom12

Registered User
Huntsville, AL
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:

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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
 
Thanks Web! I’ll order up the RG400 with BNC’s and that adapter tonight!

Intercom is a PS Engineering 1000 ii

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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
 
For the intercom work, I currently have 30’ 22ga shielded 3 conductor wire (need 24’ 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.
 
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:

5dbbc45ea8b5bdf8011e49fa392db948.jpg


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

5dbbc45ea8b5bdf8011e49fa392db948.jpg


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
 
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.

For the intercom work, I currently have 30’ 22ga shielded 3 conductor wire (need 24’ 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! I’ll order some 2 conductor wire tonight as well.
 
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
 
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

I’m guessing 11922 based on no “crew” option, but didn’t snag a photo of the backside of the box to verify.
 
rear seat wiring

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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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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 I’m going to go ahead and completely rewire the intercom, how does my PTT connect to the A200?

Here’s the radio wiring diagram:

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I *think* that I’ll 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 I’ll 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?
 
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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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, I’ll report back when done!

90a98217a5942d6d4290931a4ad4dd6f.jpg
 
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
 
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, I’ll run it that way.

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

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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.
 
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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.
 
Well, the supplies came in and I got the job done! I really wish that I hadn’t had to do part of it again, but I’m glad it’s done the right way now.

Here’s 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 didn’t. 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!
 
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
 
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.

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.
 
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
 
Simple to find out if it’s 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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