nuckolls.bob(at)cox.net
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 Posted: Wed Jan 09, 2008 8:05 am Post subject: Odd ICOM IC-A200 Power/Ground Instructions |
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At 06:41 AM 1/9/2008 -0500, you wrote:
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Tim,
My guess is that since the power uses 2 molex pins 14, R it is a
mechanical thing (1 wire per pin) the twist and solder part is BS IMHO.
The ground could be 4 18-20 ga to maintain 1 pin per crimp. these can go
all the way to the ground point or joined to 1 or 2 wires, your choice.
As far as I can see from a grounding point of view you are trying to
maintain the signal ground at the same potential as the airframe/battery.
The IR drop wants to be as low as possible to achieve this, lower than
may be acceptable for the power leads. That said you may want all 4 wires
to go to ground.
I think that the mechanical issues and the redundant contacts at the
card edge connector are the overriding concerns here. If there is another
explanation based on physics it escapes me (possible).
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When ever you see paralleled pins, the first thought
that comes to mind are desires to (1) minimize total
resistance in that conductor path and/or (2) an attempt
to 'share' total current between to pins in the connector.
I've written several times about programs I've worked on
where it was desirable to run 20 or more amps through a standard
D-sub connector. I developed this process about 10 years
ago at RAC and tried for the first time on the GQM-163 target
and currently used in numerous locations on the Hawker 4000
power distribution system.
http://www.aeroelectric.com/Pictures/Schematics/D-Sub_Power_Dist_1.jpg
HOWEVER, for this process to work effectively, you MUST
have a suitable length of wire on EACH pin BEFORE they are
joined together into a common conductor. In the case of
the ICOM (and numerous other radios) I'd put a 6" piece
of 22AWG pigtail in each pin to be paralleled and bring
the pigtails together into a common conductor at a soldered
joint or butt-splice.
The ballasting resistance of the pigtails is essential
to making the pins share the total loads.
Bob . . .
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( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
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