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Aviation Intercom System


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#1 rfrogman

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Posted 05 May 2012 - 05:55 PM

Aviation Intercom System
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This write-up is on how I install a general aviation intercom system in my ’07 JKU. This is for information only. If you decided to do the same thing I take now responsibility and you are doing it at your own risk.

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What is it? Flightcom IIsx is a small expandable and portable intercom system used in general aviation to allow a Pilot and crew to talk while flying. This system connects to the flight radio and includes a pilot isolation which allows the pilot to talk on the flight radio while the rest of the crew can continue with their conversations. It can run on a 9v battery or you can hook it into a 12v system with the included cigarette lighter adapter.

Why would you need that? I asked myself the same question. Have you ever been running around with the doors off and the top down only to find you and your passengers are screaming at each other because of the ambient noise? Well I have and the number one complaint I get is the people in the back seat cannot hear the people in the front seats. That’s why I needed it. So as I pondered, it dawned on me someone somewhere has had to figure this out. Well they did. Thanks to Google I found Off Road Intercom systems but they wanted $600. Too expensive for me but I noticed the headsets looked like the ones used by pilots. Low and behold aviation intercoms were much more affordable a little over $100 plus the cost of the headsets.

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Let’s get started:

Tools:
Philips screw driver
Drill with step bits (should be larger than the ¼” phone jacks for radio)
Vacuum or shop vac
Solder iron
Solder
Shrink wrap or electrician tape
Trim removal tool

Parts:
Flightcom IIsx
Flightcom SR4 expansion
Aviation Headsets
¼” phone to 3.5mm adapter
.206 Phone jack
PTT switch
Male 4 pin CB mic plug
CB mic wire

Installation:

First I had to find a place that was convenient to mount the Flightcom IIsx. I chose between my air vents on the center dash just below my head unit. Simply run the screws through the mounting plate. Keep in mind that the 12v power and radio cable are on top. Note that mine is just a little bellow the center dash section where the air vents are located.

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Rick "Frogman" Froggatt
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#2 rfrogman

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Posted 05 May 2012 - 05:56 PM

Here is a photo of the back of the IIsx when removed from the mounting plate. You can see where the 9v battery would go if you choose not to use a 12v power source.
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To mount the unit simply align the mounting tabs with the holes on the back of the IIsx and firmly push down. Here you can see the pilot isolation switch I was talking about before.

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Next I drilled a wire routing hole just to the top left of the IIsx. I ran the power wire to the 12v/ignition on socket (you may want to run this to the fuse box instead). The radio audio plug went into the ¼” to 3.5mm adapter then into the speaker out of my CB. I also have a speaker Y-adapter inline so I can hear the CB if I’m not running the headsets. The IIsx mic plug is not hooked up yet. I have to fab an adapter cable using the .206 jack, CB mic cable, PTT switch and 4 pin CB plug.

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I also drilled a small hole under the unit though the center dash to route the extension cable for the SR4 expansion box. It’s cable looks like a phone cable but the small end goes in the bottom of the IIsx unit and the standard RJ11 plugs into the SR4. I will have to extend the cable later. Since the cable wasn’t long enough I just put it in the cup holder for now.

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Conclusion:
Flightcom IIsx with SR4 expansion allows four people to talk in normal voices with loud ambient noise around. This setup should be used off road although fire trucks, ambulances and military vehicles use similar systems while driving on pavement. Please check the laws in your area before running down the road with these on.

Enjoy!
Rick "Frogman" Froggatt
De Oppresso Liber!
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#3 rfrogman

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Posted 05 May 2012 - 05:56 PM

This is a simple homebrew PTT switch adapter that goes inline between the aviation intercom Mic out and my Midland CB.

Note: This is specific to Midland. it will not work on a Cobra CB. You will need to reference your CB radio's schematic for pin-outs.

Aviation mic to Midland 1001z CB radio adapter.

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Aviation headsets and intercoms use a PJ068 Plug (.206" 3 conductor) which is smaller than the standard 1/4" phone plug. The smaller size prevents the operator from putting the headset audio plug in the Mic jack. These date back to the telephone switch board operator days.

PTT (Push to talk) is accomplished by grounding the TX pin using a momentary switch. I added two .01 uf and one 470 ohm to prevent feed back (squealing) from the microphone.

Here is my simple circuit that is inside the project box.

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This is the mic circuit from the 1001z main schematic.

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All hooked up with the doors off.
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Rick "Frogman" Froggatt
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#4 VolsJK

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Posted 06 May 2012 - 11:05 AM

That's a pretty cool idea. Too bad I took my backseat out ;)

Matt

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#5 JCJ

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Posted 06 May 2012 - 01:58 PM

Cool idea! Not sure I have a need for such a setup. My son is usually in the back, but he mumbles so I'm accustomed to not really understanding him most of the time anyway.

#6 MikeJeep

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Posted 06 May 2012 - 02:36 PM

One thing to remember is that it's illegal to cover up BOTH ears while driving (that includes using two earbuds), but you never see cops giving tickets for it.

#7 Obiwan

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Posted 06 May 2012 - 07:33 PM

One thing to remember is that it's illegal to cover up BOTH ears while driving (that includes using two earbuds), but you never see cops giving tickets for it.


Maybe because cops don't usually encounter drivers with a big fat David Clarke headset on their ears? :)

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#8 TN12valve

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Posted 08 May 2012 - 09:23 AM

I grew up in So. Cal. and spent most weekends of my childhood in the dunes of Glamis and Dumont. These intercom systems are a huge deal out there. EVERYONE with a sand car has a set and they do make a world of difference! This is the first set that i have seen in a Jeep though. Nice job! I might do something like this as well but i would like to have it link into my CB like most of the offroad ones do.

~Brady
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#9 rfrogman

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Posted 09 May 2012 - 06:07 PM

I grew up in So. Cal. and spent most weekends of my childhood in the dunes of Glamis and Dumont. These intercom systems are a huge deal out there. EVERYONE with a sand car has a set and they do make a world of difference! This is the first set that i have seen in a Jeep though. Nice job! I might do something like this as well but i would like to have it link into my CB like most of the offroad ones do.


I am working on making a CB/PTT adapter for the aviation mic plug. I am waiting for the .205 jacks to come in from mouser. I will post pics and the wiring diagram in the third (reserved) post when I'm done. i have the pinouts for Midland and Cobra mics. Also you can use common 8 ohm stereo system headsets with an aviation microphone as a low cost alternative to the full aviation headsets. Although I picked up three aviation headsets for $80 off ebay which is less than one at retail prices.
Rick "Frogman" Froggatt
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#10 SherpaOfBadDecisions

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Posted 09 May 2012 - 08:41 PM

No offense Rick, but when I started reading this,my WTF meter started going off. I kept reading and that is an awesome idea. could you route your cb through it and other radio systems????

edit I reread some of the posts and misunderstood some of the abbreviations. Soooo yes I see you are working towards the radio routing.

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#11 rfrogman

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Posted 10 May 2012 - 06:54 AM

It's a simple mic setup so depending on the type of mic connection your radio uses you my have to adjust the pinouts. I have the Audio out already connected. They do make an adapter that will work with Icom hand held radios.
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#12 rfrogman

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Posted 29 May 2012 - 08:06 AM

Updated wiring for my Midland 1001z CB.
Rick "Frogman" Froggatt
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