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What needs shielding on Flightcom harness?

A

alpinelakespilot2000

Well Known Member
I'm not clear on the shielding requirements for my Flightcom 403 harness:

The flightcom installation manual indicates:

"• Use shielded wire for microphone, headphone, and audio wiring."

Of the 25 pins on the DSUB, which fit into this category? Am I looking for one of those 3 terms in the pinout name shown on the pinout chart below? If so, does that mean only wires 2, 3, 4, 9, 10, 11, 12, 14, 15, 16, 17, and 21 need shielding? Or, do some of the other pinouts require sheilding even though their names don't include those three terms?

http://www.flightcom.net/pdf/403-403dManual.pdf

Can anyone who's been through this let me know which pins need shielding?

Also, I assume that single conductor shielded wire is what I should use?

Thanks.
 
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why single stranded? :) I used 3-conductor shielded wire for the jacks.. got the wire from B&C, but I think Stein has it as well. works just fine w/ no noise. figure out how many leads you need and you can use eihter 3 or 4 conductor shielded wire....
 
I used 3 conductor shielded wire to the mics and headphone jacks for my flightcom 403. I used 2 concuctor shielded for the audio input. I connected the shields and ground for each of these to pin 1 of the intercom.
 
Thanks. I guess if there is no interference/noise issues, multi-strand wire would make sense if the wires are going to the same location anyway.

Am I correct to assume, given the installation manual's wording, that the PTT switches or power wires don't need to be shielded? Seems like the PTT wires would be carrying audio, which would thus require shielding.
 
Below is the schematic I used to wire my Flightcom 403d intercom. I used 3 conductor shielded wire for the mics and headphones. I used 2 conductor shielded for the aux input. I also used 2 conductor shielded for the push-to-talk circuits since one of the signals going to the PTT button also goes out to the mic. This may not have been necessary but since I already had the 2 cond shielded wire I decided to use it. I also made sure to isolate both headphone and mic jacks from frame ground. The Flightcom instructions indicated it was not necessary to isolate the headphone jack but it was recommended to me this should be done to minimize any noise.
rv9wiring35vz0.jpg
 
Thanks Joe, that's a fantastic drawing! The numbered blocks to the right of the intercom DSUB... are those terminal blocks or do they represent something else?
 
No shielding nexessary on power or PTT wires.

alpinelakespilot2000 said:
Am I correct to assume, given the installation manual's wording, that the PTT switches or power wires don't need to be shielded? Seems like the PTT wires would be carrying audio, which would thus require shielding.
Click to expand...
The PTT only grounds to key the transmitter. There is no signal on the PTT or power lines.
 
They are pin numbers on Molex connectors I used. Maybe not the best connectors but they work fine for me and they are affordable.
 
Mel,

As I noted, the same signal (wire) going out to the PTT button also goes out to the microphone. Any noise induced in the PTT signal (wire) would also go out to the microphone in the shielded bundle. If noise was present on the signal (wire) from the PTT button it could be induced into the low level signal wire coming in from the microphone. Anyway, that in addition to the fact I already had the 2 cond shielded wire is why I used it.
 
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Funny...

My Sigtronics 200S doesn't required shielded wires of any kind and I don't have any problems with it.

It makes me wonder what the difference is.
 
Connecting Flightcom 403 to Garmin SL40...

This is a great thread and helps a lot in my installation. But I have a few other questions. I'm using an Flightcom 403 and a Garmin SL40. The SL40 has a separate pin for audio ground and mic ground. The diagram shows the audio and audio ground connection in a duo shielded pair, and the mic and mic ground in a duo shielded pair. They show these going to a corresponding audio/audio ground pair and mic/mic ground pair on the "audio panel". But the Flightcom 403 does not have a unique ground for audio and mic. It has a single ground pin. So I'm not sure how to connect the SL40 to the 403.

Can someone clarify this for me?

Thanks,
Michael-
 
Run separate wires, within shielded bundles, for the mike lo and audio lo from the SL40, just as diagramed. Connect both of these wires to ground at the intercom. Also ground all shields there, and only there.
 
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