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Date: Wed, 04 Mar 2009 20:15:05 -0500
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Subject: RE: [LML] Re: TruTrak autopliot and RF
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Thread-Topic: [LML] Re: TruTrak autopliot and RF
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From: "Kevin Stallard" <Kevin@arilabs.net>

My question is, if you have to create a path for HF signals to return to
their sources (i.e. the 50 pf caps), how are they getting superimposed
on those lines in the first place?

I wonder if it is radiated noise or conducted?

Kevin

-----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of
John Schroeder
Sent: 2009-03-04 11:34
To: lml@lancaironline.net
Subject: [LML] Re: TruTrak autopliot and RF

Chris -

We used the same items as did Steve. They come in various capacitance
and =20
according to the chart on the Amphenol website, 50 pico farads would =20
capture the com band frequencies. The principle is that each pin has a =20
capacitor between the top of the pin (input) and  ground (case) to shunt

rf energy to ground. We put one on between the connector and the tray
and =20
also on each of the servos. Our com antenna #2 was in the starboard wall

of the baggage compartment (ES) and it also had an effect on the EFIS.
We =20
went to an external com antenna on the belly as #1 and made the one in
the =20
vertical stab #2. We also put baluns on each of the power cables (fat =20
wires) where they interfaced to the panel and then on the feeder cables
to =20
the busses. This solved most all of the RF problems - except for the Ray

Allen trim indicators. They still dim when we transmit. We also
performed =20
the installation test for RF prescribed in the Garmin GNS 480
Installation =20
Manual. We had no RF interference with the GPS.

Allied Electronics/Electric also has a product similar to the Amphenols.
I =20
ordered one to try in case the Amphenols didn't work. So, I don't know
its =20
effectiveness.

Hope this helps.

John

On Wed, 04 Mar 2009 08:13:24 -0500, Steve Richard =20
<steve@oasissolutions.com> wrote:

> I used this and it helped:  =20
> http://www.vonero.com/index.php?/showproduct/853439
>
> Steve Richard
>
> Chris Zavatson wrote:
> A recent upgrade to more powerful com radios has introduced a bit of
an =20
> undesirable problem with the Trutrak autopilot.  When the auto pilot
is =20
> engaged and the #2 radio is keyed, serious pitch oscillations occur.


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