GTN 650 conversion Antenna Encoder and fan Questions

[jeffsvan]

If one wants to convert from a 430W setup to a GTN 650


1. Does the GTN650 need an avionics fan? I am reading it has one built in.

2. Does the GTN650 have and internal antenna splitter similar to the SL30 ? DO you only need one Nav coax and it splits Glideslope, VOR, Localizer internally?

3. I have read something about inputing Marker beacon signal into the GTN 650. How does this work?

4. Can you use an older Encoder (Grey Code) with the GTN if you add a Serializer such as an Icarus 3000U to convert the signal to 9 pin RS232 ?

5. Can one use the pre existing GPS antenna and 13 foot cable from the 430W ? or does the GTN use/need somehing else?

Are there any other differences between a conversion from 430W to GTN 650 that could be more costly $ to the installer? i.e. need to buy other hardware

[g3xpert]

Jeff,

There are several considerations when converting the GNS 430W to the GTN 650 as you have listed.

1. The GTN 650 does have a cooling fan built on the installation back plate that draws air through the GTN 650. This fan does adds a 1/4 inch of length to the installation rack over the GNS 430W.

2. Yes the GTN 650 does have an internal splitter for VOR and Glideslope signals. This does allow the NAV antenna to be connected directly to the GTN 650. This is assuming the GTN 650 is the only NAV receiver in the aircraft.

3. The GTN 650 does not display the marker beacon lights. Only the GTN 750 does and only the marker receiver that is in the GMA 35 remote audio panel.

4. The GTN series units do not accept grey code altitude. Any altitude source has to be on a serial (RS 232) input. The convertor should work as long as it puts out the correct format at the correct baud rate. The GTN can accept either a Shadin format or an Icarus format altitude at 9600 baud rate.

5. Yes you can use the exsiting GA 35 or equivelant antenna. Page 1-9 in the STC installaton manual has a table of antennas that will work with the GTN 650. The 13 feet of cable is fine and should be either RG 142 or RG 400 if not already.


Keep in mind there may be some wiring changes as the GTN is not pin compatable with the GNS units. The COM antenna should be fine also. Otherwise no other hardware should be needed for the conversion.

Garmin Tim

[jeffsvan]

The need would be to split one Nav cable into two radios.

I have one cat whiskers Nav antenna.
I would need to split it 50/50 between a GTN650 and a SL30 radio.

Is there a recommended splitter?
I had read somewhere that Garmin recommended a specific model.

Im thinking Comant CI-5120 since both the GPS and radio have internal diplexors?

[SteinAir]

Originally Posted by jeffsvan

The need would be to split one Nav cable into two radios.

I have one cat whiskers Nav antenna.
I would need to split it 50/50 between a GTN650 and a SL30 radio.

Is there a recommended splitter?
I had read somewhere that Garmin recommended a specific model.

Im thinking Comant CI-5120 since both the GPS and radio have internal diplexors?

That is correct for your application!

Cheers,
Stein

[jeffsvan]

a few more questions.

the two wires rs232 and ground coming from the Icarus serializer going to the GTN650... does it have to be shielded wire? The other encoder to transponder wire (grey code) is not.

Looks like a boo boo in the harness. They may have wired the connector on the OBS for a mid continent MD200 instead of the GI-106A which is what I have. It looks like its only 1 or 2 pins I have to swap. is this correct?

Pin # 18 BCC/VLOC is one of them.

[g3xpert]

Originally Posted by jeffsvan

the two wires rs232 and ground coming from the Icarus serializer going to the GTN650... does it have to be shielded wire? The other encoder to transponder wire (grey code) is not.

Jeff
The RS 232 from the Icarus serializer should be shielded wire. Many times in the past the grey code wires weren't shielded but they are a discrete input and not a serial data stream.

Originally Posted by jeffsvan

Looks like a boo boo in the harness. They may have wired the connector on the OBS for a mid continent MD200 instead of the GI-106A which is what I have. It looks like its only 1 or 2 pins I have to swap. is this correct?

The connections in the installation manual for the GTN 650 show the same pin connections for both the MD 200 and GI 106A for the OBS information. The MD 222 is the Mid Continent annunciation unit that is different from the GI 106A for OBS information.

Originally Posted by jeffsvan

Pin # 18 BCC/VLOC is one of them.

The GI 106A does not have a BC annunciation in it. You can use the VLOC and GPS annunciation lines from the GTN to drive the lamps in the GI 106A. To do this use pin 15 from the GTN P1001 connected to pin 17 on the GI 106A for GPS. Connect pin 52 P1001 on the GTN to pin 18 on the GI 106A for the VLOC lamp.

The AML STC installation manual for the GTN 650 has a drawing on page E-19 showing all the analog indicators the GTN will interface with. You can cross check different indicator connections to the GTN with this drawing.

Garmin Tim