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Old 02-04-2021, 06:07 PM
alcladrv alcladrv is offline
Join Date: Oct 2006
Location: Southeast
Posts: 614
Default Co-pilot comm wiring

I'm trying to wire up my GTR200 to use its built in intercom, with its separate inputs for both pilot and co-pilot. In reference to the Dual Comm Audio Wiring attached drawing, it looks like the inputs for only one pilot are shown. To get both the intercom and the Transmitter Select Switch functionality, does the co-pilot wiring simply parallel the pilot wiring and connect at the same points?

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Name:	Dual Comm without Audio Panel.pdf
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Old 02-04-2021, 11:44 PM
BobTurner BobTurner is offline
Join Date: Dec 2011
Location: Livermore, CA
Posts: 7,348

The diagram you show is 20 years old, and pre-dates com radios with built in intercoms. The GTR 200 has separate mike inputs for pilot and copilot. However, the GTR was really designed for airplanes with a single com. If you want to use two of them you will need external switching for both mikes between radios, multiple 100 ohm resistors on the headphone outputs for isolation, etc. If the second radio does not have a built in intercom it can still be done, but itís complicated. Most people with two coms put an intercom between the mikes and radios, and donít use the built in intercom. But it can be done with manual switches.
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Old 02-05-2021, 04:28 AM
alcladrv alcladrv is offline
Join Date: Oct 2006
Location: Southeast
Posts: 614

Thanks. After flying with a single SL30 and a portable intercom for many years, I was planning to add the GTR200 as the primary radio, using its built-in intercom, and use the SL30 as a 2nd comm. If I can switch to the SL30 to transmit or just listen for a bit without switching and then switch back to the GTR for primary usage then that would most likely meet my needs.
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Old 02-06-2021, 01:08 AM
BobTurner BobTurner is offline
Join Date: Dec 2011
Location: Livermore, CA
Posts: 7,348

Send me a PM with your email address and Iíll send several suggestions for how to do this.
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Old 02-06-2021, 01:17 AM
jliltd jliltd is offline
Join Date: Sep 2013
Location: Rancho San Lorenzo
Posts: 1,008

With two coms like that (and a VOR identify function) you really need an external audio panel. Yes, there are work-arounds that provide acceptable alternatives but they are DIY projects so if you go that route make sure you like to tinker with electronic projects as much as fly. Kind of like installing an automotive engine or carving your own prop. Nothing wrong with that. And so it is with respect to audio there is a good reason most aircraft with more than one radio use a separate audio panel.

The GTR200(B) has an excellent internal intercom that is intended to cater to the single-radio two-seat crowd. The best thing this side of the original SL40 which had a more rudimentary ICS built in. The GTR 200 is an equally great choice as a second com in a multi-radio installation with a separate audio panel and it's ICS functionality disabled.
(a few more airplanes too)

Last edited by jliltd : 02-06-2021 at 01:20 AM.
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