|
"Tri-Pacer" <nospam@hotmail.com> wrote in message
news:d6WdnRz_KeTM3vbZRVn-pA@comcast.com...
>
> Got out to the hangar with my watt meter to see if I had a high VSWR that
> might be putting RF where it wasn't wanted. When I turned the slug to the
> reflected position, the meter reading was so low I could barely read it.
> That eliminated that possibility.
>
> I next found out that I could not duplicate the problem. The only
difference
> this time was that the top cover over the instrument panel had been
removed
> for access. I called EI in Bend Oregon for some tech assistance.
>
> Their take on it, was that the garbage was getting in via the ground
lead!!
> They said to shorten it and the trouble would be gone. Since they make the
> instrument and have seen this before, I followed their instructions,
pulled
> the ground lead off the buss and made a separate ground as close to the
> instrument as possible. I did fudge a bit and wound the ground lead
through
> a ferrite bead right where it exits the instrument case. They kind of
> ignored my comments that the problem only occurred with the radio was
keyed
> AND the strobe was on.
>
> If this does it great. If not I think my next attack might be to get a
> ferrite bead on the power to the strobe up on top of the vertical
stabilizer
> and filter the input to the fuel flow instrument. I've a skylight in my
> PA22 and looking up through it while fiddling with the wiring I see the
> antenna is perhaps 24 inches from the instrument. I guess not too many
> fabric airplanes have fuel flow instruments installed. :-(
>
>
> Thanks Jim for the tip on the hash being additive and hitting a threshold
in
> the instrument.
>
> Cheers:
>
> Paul
> N1431A
>
>
Why would you want to add inductance back into the ground lead that you just
shortened (eg reduced inductance and resistance). Ditch the ferrite bead in
the ground lead. If you really want to use it put it in the power lead.
Good Luck
Jim Stockton
|
|
Re: oddball RFI problem Update
