In a message dated 2/20/2009 3:02:52 A.M. Eastern Standard Time,
europa-list@matronics.com writes:
>>>>>I know that this may be a little late for those of you who have already
bought their strobe power units, but my installation works well without
any interference. I have Whelen equipment and I mounted an HTS power
supply at each wing tip. They are mounted on removable panels on the
bottom surface. There is a weight penalty of about 1 pound compared to a
single HDA power supply in the fuselage but all the high voltage cables
are short and at the tip. No problems.<<<<
Hey John and all,
Follwing the K.I.S.S. principle, I used a single Whelen strobe power supply
mounted to one of the vertical baggage bay support members under the port
side of the baggage bay and my install does not cause any audio interference
whatsoever. Access to the power supply is through the port access cover in the
baggage bay floor. The power supply fires strobes on the wing tips with the
cables routed from the power supply along the bottom side of the baggage bay,
then along the sides of the baggage bay in the cockpit in fiberglass raceways
which extend from the baggage bay bulkhead forward to the rear of the door
sill. I installed these raceways along and over the fuselage seams on the
sides of the baggage bay, covering the seam, as well as providing a conduit for
wiring. The wires then pass down into the backrest and out the side of the
fuselage through grommeted holes in the fuselage sides just behind the spar
opening in the side of the fuselage. The raceways I made were molded over a
piece
of 1.5" PVC pipe cut lengthways to produce a 1/3rd round shape. Then with
the PVC taped to a piece of plywood, 3 layers of 'bid were used to make the
molding. A 1/2" flange was left either side of the rounded part to leave a
bonding flange for bonding to the inside side of the fuselage.
My system is quiet as a mouse without the faintest hint of strobe tick. The
secret to keeping your strobes quiet first and foremost is how you ground the
shield wires on the strobe high tension feeder cabling. The shield wires
should be grounded only on the power supply end. I crimped, then soldered a
ring
terminal to the shield wire at the power supply end of the strobe wires,
then landed the ring terminal under one of the mounting screws for the power
supply so that the shield wire has continuity with the power supply case (which
is grounded). Do not ground the other end of the shield wire at the light. If
you do, you will create a loop antenna and a host of problems will follow.
I used six pin Molex plugs and sockets at the wing roots and fuselage sides
so that I would be able to disconnect the strobe and Nav light wiring when
the wings are removed. The shield wire must also be carried through at this
point. At the light end, I simply cut the shield wire off even with the cable
jacket and stuck a piece of heat shrink tubing on the strobe cable to make it
look pretty, allowing the strobe feeder wires to carry through a few inches
beyond the cable jacket. The strobe feeder wires exit the end of the heat
shrink, along with the NAV wires which are routed on the outside of the strobe
cable, taped to the strobe cabling about every 6" along the length of the
strobe
cable and then carry on to the NAV light. I also installed 6 pin Molex plugs
at the light to make for easy removal of the light if and when it fails, but
the shield does not need to be included here. The plug/socket on the light
end makes for easy removal of the light fixture for replacement of the strobe
and NAV bulbs when the time comes or replacement of the fixture should it
become damaged, but this step could be omitted. Another thing that is very
important is to not route any other wiring with your radio and intercom audio
wires, especially the strobe feeds and the trim motor wiring. Keep all other
wiring separated from your audio wires by at least a few inches.
I've installed Whelen strobe/Nav combo lights, grounding the shield in this
manner, in 3 different airplanes thus far and all three are/were quiet as a
mouse.
Hope it helps!
Regards,
John Lawton
Whitwell, TN (TN89)
N245E - Flying
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