Message-ID: <004501be7b89$389b7240$bc818ed1@pavilion>
From: "J. N. Cameron" <CIC@centuryinter.net>
To: "Lancair List" <lancair.list@olsusa.com>
Subject: Noisy E.I. engine instruments
Date: Wed, 31 Mar 1999 09:14:48 -0600
Mime-Version: 1.0

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>>
    My Super ES has been flying about two months, with a full complement of
Electronics International engine instruments, plus Jim Frantz' annunciator
panel.  With my initial wiring installation, there has been a serious
problem of RF interference with the EI gauges; whenever the mic was keyed to
transmit, the gauges went crazy and triggered both alarm lights and the
audio alarm on the annunciator panel.
    With helpful hints from Sy at Lancair, Jim Frantz, and my local
avioniker (Joe McKee, @HYI), I seem to have solved most of the problem.
    Step 1:  Tear out and re-route the antenna cables for COM1 and COM2.
These originally had gone back along the left side with most of the other
wiring.  Now routed all alone down the right side, kept carefully away from
the wiring to the rt side fuel probes.
    Step 2:  Added ground straps to the metal panel sections, and to the
radio racks.
    Step 3:  Built a shielding box over the heads of the fuel probes from
heavy copper foil, enclosing the wiring out to the three spade connectors.
Soldered a ground wire to the foil shield, then brought the ground wire back
to a heavy ground post connected to heavy gauge ground bus.
    Results:  Ground testing indicates great improvement.  Now with COM1
keyed (antenna in v stab), there is not even a flicker, and with COM2
(antenna much closer, in baggage compartment wall), the left side tank
indicates a slow rise in fuel level, but not enough to trigger alarms.
    It seems this is a common problem.  If I were installing from scratch
today, I would make a neater shield over the fuel probes, then figure a way
to run fully shielded cable from the probes right to the instrument case.
    The Oil Temp/Press gauge was also giving some spurious alarms, but seems
to have improved.  Weather is nice today, so I'll flight test and add to the
report if new problems show up.