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1. 08:02 AM - Re: Re: Aera 660 Bare Wire Cradle Question (Robert L. Nuckolls, III)
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| Subject: | Re: Aera 660 Bare Wire Cradle Question |
>
>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 systems=853.) 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 . . .
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