I had someone much smarter than me place an oscilloscope on my panel power supply.  He noticed a small AC on the line during transmission.  I think it was between 1 and 3 volts (but it was a few years ago and my memory is fading).  We never investigated any further because the filter seemed to help eliminate most of the problem.  I was wondering if someone could duplicate this issue or speculate on what problems it could cause?

Steve

Kevin Stallard wrote:

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  
according to the chart on the Amphenol website, 50 pico farads would  
capture the com band frequencies. The principle is that each pin has a  
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  
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  
went to an external com antenna on the belly as #1 and made the one in
the  
vertical stab #2. We also put baluns on each of the power cables (fat  
wires) where they interfaced to the panel and then on the feeder cables
to  
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  
the installation test for RF prescribed in the Garmin GNS 480
Installation  
Manual. We had no RF interference with the GPS.

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

Hope this helps.

John

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

  

I used this and it helped:   
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  
  

undesirable problem with the Trutrak autopilot.  When the auto pilot
    

is  
  

engaged and the #2 radio is keyed, serious pitch oscillations occur.
    

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