Mark what kind of antennas are you using? If tape was the coax
connected in the center. I assume they and the coax are
bonded in
so there is little you can do about changing anything having
to do
with that.
The other thing I am curious about is the new box that
converts
the fuel sensor value to a variable frequency pulse. Please
look
inside
and tell me the numbers on the chips if they are readable of
course.
Some manufacturers mask the numbers sometimes so it makes it
more difficult to copy the circuit.
The diodes Aubrey mentions may be embedded in the chip or
chips what
ever the case may be. In that case the only thing I think
you can
do is put them in a shielded box and move it away from the
coax.
--
Paul Lamar ...No rotor no motor.
Paul (and others),
I made a breakthrough this weekend on the fuel probe problem. I
rewired the right probe with shielded wire from the probe all
the way to
the EFIS. Power up the EFIS and Nav/Com, hit PTT, and the gauge
is
steady as a rock. The left gauge (the one that I haven't
changed) still
acted up as always, but it will be next to fix. But the right
one with
shielded wire appears to be working great. It was too late in
the day
to fly it, but I feel 99% certain that this has corrected the
problem.
Thanks to everyone that shared their ideas and suggestions on
how to fix
this very annoying (and potentially dangerous) problem.
Mark S.
25.5 hrs
Congratulations Mark. You had a real bear of a problem there for
awhile.
These kinds of problems usually require real expensive instruments
to trouble shoot like field strength meters and VSWR meters.
Probably a good plan of attack is shield everything in an airplane
including all the engine computer wiring.
--
Paul Lamar ...No rotor no motor.
Paul,
I have heard of others having this same type of problem with
capacitive
fuel gauges. You would think the manufacturer would provide some
guidance/assistance on how to correct this problem. Oh well, such is
EXPERIMENTAL aviation. Thanks for your help.
Mark
They mostly deal with metal airplanes and they provide a better ground
and some shielding. Also RG400 is the correct coax for metal airplanes
with quarter wave antennas.
I am still curious about your antenna. Did you use a tape antenna?
Send me private email if you want to keep it on the QT :)
Here are a couple of shots from that SA mag composite plane antenna
article.
I think you can just barely see where the coax is connected to the
half wave antenna in the detail photo.
BTW I notice that Cessna bought Columbia so you and Tom Parkes now
own Cessna's :)
I also notice Cessna opened a plant in China for LSA aircraft.
--
Paul Lamar ...No rotor no motor.
Mark's using a Bob Archer - he said so in a message I received on 2/14:
"Matt,
I can be heard very well, or so I'm told. My nav/com is an SL-30 with a
Bob Archer antenna in the tail. It was tested by a ham prior to
installation and checked out very well (don't remember the numbers).
Coax is RG-400 and is one piece from the antenna all the way up to the
radio. The fuel gauges are the only thing that seem to be affected by
the radio.
Mark"
Regards,
Matt-
Sorry! That got lost in my mind :)
http://home.hiwaay.net/~sbuc/journal/bob_archer.htm
Sounds like they are for metal airplanes only with composite wing and
rudder tips. Any RF on the outside of the coax would be shielded by
the metal wings or vertical tail. I'll cc this to Bob.
I suspect the VSWR and the radiation pattern are different
if installed in a totally composite airplane.
--
Paul Lamar ...No rotor no motor.
Hi Guys:
I am not sure who sent me this message.
I will attach a paper I wrote on the subject of aircraft electrical noise
and RF interference.
I would be happy to help solve any of these problems.
Bob
That was me Bob. Thanks for the paper.
Paul Lamar ...No rotor no motor.
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