---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Tue 06/11/19: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:35 AM - Re: Aera 660 Bare Wire Cradle Question (farmrjohn) ________________________________ Message 1 _____________________________________ Time: 07:35:08 AM PST US Subject: AeroElectric-List: Re: Aera 660 Bare Wire Cradle Question From: "farmrjohn" nuckolls.bob(at)aeroelect wrote: > > > > > but the current installation manual, dated 6 months later, states: > > "A three conductor shielded cable 24 AWG or heaver, > > Hmmm . . . . Given the short runs and low > power levels it seems unlikely that > anyone experienced degraded performance > as a consequence of voltage drops. However > 24 AWG is about the smallest practical > size for hand-assembled wiring and even > that was not well received on our production > lines at RAC/Beech. I've personally never > designed an airframe harnesses with smaller > than 22AWG wire . . . works good, lasts > a long time, easy to work with. > > > > (Aircraft Spruce P/N 11-04478 or equivalent) should be used to connect > > the ELT RS 232 data and power to the aircraft systems3.) Connect one > > conductor to pin 3 (Fig. 12.1) and connect to aircraft ground at the > > cockpit. connect the outer shield to ground, at the cockpit end only." > > In what document does figure 12.1 > appear? I'd like to look at it if > it's downloadable . . . > > This is best practice . . . unless the > shield is a CONDUCTOR of data or power > by design. I.e. I used to build a lot > of RS232 runs from 22AWG shielded, twisted > pair where the shield was used as signal > ground for the TX/RX pair. > > But if the shield is simply a prophylactic > against electro-static coupling of noise, > then a ground at one end will suffice and > avoid other potential difficulties with > ground loop currents on the shield (a > potential problem on large, all metal > aircraft . . . something I've never seen > but it was talked about in EMC class). > > In any case, the best approach is to follow > the manufacture's installation instructions > unless you've been made aware of some error > on the part of the folks who wrote the > manual. > > > > If using individual wires, should the shield be grounded at both ends or just at the aircraft ground as if using the three conductor cable? > > A you planning on building your own > shielded run of wires? > > > > Also, if using the three conductor cable, what would be the best > > way to separate the 232 data wire from the power and ground wires? > > Don't understand. One cable would carry > RS-232 . . . an independent cable would > carry power . . . no physical 'separation' > necesasry. > > > > They will not be connecting at the same place since the power > > source is not coming via the 660 cradle harness. > > Not a problem > > > > Bob . . . Fig. 12.1 is from the ACK model E-04 installation operations manual and is downloadabl:. https://www.ackavionics.com/e-04-technical-information/ I would consider building my own run of wires using a shielded wire for the 232, and unshielded for power and ground. My question about separating the wires from the three conductor cable deals with getting the necessary length for the power and ground leads since they won't connect in the same location as the d-sub where the 232 wire does. A solder sleeve for the ground wire and shield will work to get the added length necessary to get to the ground point and I suppose splicing and additional length to the power wire would work. Or, I could try stripping off the outer insulation of the cable then cut back the 232 wire to length before connecting to the d-sub. 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