G5 / GFC500 Install Info

[ArtVandelay]

Wouldn’t the old coax ethernet cable be better for lightning protection certification tests? Plus no pins, other than power it would be easy to install.


Tom

[johncuyle]

5 hours ago, bob865 said:

Here ya go

https://en.wikipedia.org/wiki/OSI_model

If I made a mistake, let me know where.  This stuff is a random interest of mine so I'd seriously like to know.

I think he's referring to the earlier linked comparison article, which inexplicably mentioned TCP and security, which live up in the transport and presentation layers according to the OSI model.

[Yetti]

5 hours ago, ArtVandelay said:

Wouldn’t the old coax ethernet cable be better for lightning protection certification tests? Plus no pins, other than power it would be easy to install.


Tom

I think the point of the Garmin speced cable that it was 120 ohm.    most of the regular network cable is 100 ohm.    not sure what the old stuff is, but the old token ring which was coax was either 50 or 75 ohm.    Can't Remember.     But you needed to have terminators on the blank ends.  Which was outer braid to center core with a 50ohm resistor.    For interference reduction with a network cable you twist the pairs.  The lectrical gineer will be along to explain how twisted pair works

[Emmet]

The 120 value describes the wave impedance and not resistance. This is important for reflections on the cable.

[bradp]

Regarding the Carlisle brand - seems as though this AC would allow substitution of the brand of it adheres to a standard (IEEE etc).  

Am I reading this correctly ?

 

[201Mooniac]

It sounds like there will be a new rev 18 of the install manual posted soon that will remove the requirement for the Carlisle wire for most installations.

[Deb]

From Trek Lawler (Garmin Field Service Engineering Supervisor) posted on BeechTalk 4/17/2019 https://www.beechtalk.com/forums/viewtopic.php?f=21&t=166081&start=105:

Hello everyone,
we just received approval on the revision 18 of the G5 install manual which updates the type design data to reintroduce shielded twisted-pair cable, MIL-C-27500 as an optional wire type for use in CAN bus installation and other minor clarifications to the STC Installation manual.

we will have the new manual posted here very soon.

let me know if there are any questions,

 

[hypertech]

A CAN bus is a differential signal and very resistant to noise.  It should be a twisted pair, preferably shielded.  The wire impedance and resistor terminations are also important.  With more devices connecting to the bus, it may be that they need to be more careful there.

I don't know what they spec'd before, but the new spec makes sense to me and I would want that even if they called it "optional."  The difficulty bit with aviation is that the wire that everybody else in automotive, marine, etc probably doesn't meet the safety standards for aviation wire (off gassing if it burns, etc).  

Given that that wire is going to be in the plane for probably 20+ years, I wouldn't be in a hurry to get the old spec wire installed.  Its probably worth waiting to get the right wire pulled.