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Com issues - resolved

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berkut13(at)berkut13.com
Guest

Posted: Fri Feb 16, 2007 8:54 pm Post subject: Com issues - resolved

Well gang...it's fixed.



I added 150ohm resistors to all input audio leads into the panel. 

Everything is living together quite nicely now.  I guess something in the 

combination was not playing well with the new radio.



However, there was one wild card that might also have something to do with 

it.  While I was removing, moving, installing, and re-installing the pins in 

the 134's connector, one of the ground leads (mic I think) broke off a pin. 

I was forced to strip and crimp a new molex pin on there and re-secure. 

This was done in the same operation as the resistors.  After all that, the 

audio was loud and clear with all radios mixed in, regardless of the 

combination.  I'm not convinced this was the issue, since the radio did work 

correctly by itself.



So...was it the resistors?...was it a bad ground?...was it a gremlin? 

Personally, I don't care anymore...it's fixed!



Thanks for all the help, everyone.  Nothing like beating your head against 

the wall in a cold hangar.



James Redmon

Berkut #013  N97TX

http://www.berkut13.com

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nuckollsr(at)cox.net
Guest

Posted: Sat Feb 17, 2007 6:27 am Post subject: Com issues - resolved

At 10:47 PM 2/16/2007 -0600, you wrote:



 	  Quote: 	
		  



Well gang...it's fixed.



I added 150ohm resistors to all input audio leads into the panel. 

Everything is living together quite nicely now.  I guess something in the 

combination was not playing well with the new radio.



However, there was one wild card that might also have something to do with 

it.  While I was removing, moving, installing, and re-installing the pins 

in the 134's connector, one of the ground leads (mic I think) broke off a 

pin. I was forced to strip and crimp a new molex pin on there and 

re-secure. This was done in the same operation as the resistors.  After 

all that, the audio was loud and clear with all radios mixed in, 

regardless of the combination.  I'm not convinced this was the issue, 

since the radio did work correctly by itself.



So...was it the resistors?...was it a bad ground?...was it a gremlin? 

Personally, I don't care anymore...it's fixed!


	


    I suspect that your victim radio was being loaded down by

    and exceptionally LOW output impedance of the other radio.

    With its low output impedance, it was able to deliver useful

    audio output energy into a system that was "loaded" not only

    by the system that drove you headphones but by the other

    radio. This is the phenomenon explained in the audio systems

    chapter I cited earlier.



    Adding the resistors artificially raised the output impedance

    of all sources. This degrades the transfer of energy to the

    headphones . . .but no so much that increasing radio volume

    can't overcome it. At the same time, it breaks the ability

    of a radio having exceptionally low output impedance from

    exercising the loading effect you were experiencing.



    Bob . . .



        ----------------------------------------

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

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berkut13(at)berkut13.com
Guest

Posted: Sat Feb 17, 2007 7:04 am Post subject: Com issues - resolved

Yep, I read that chapter and found it very enlightening.  When I was wiring 

up the airplane, I skipped that section since I out-sourced the panel wiring 

harness to a local avionics shop. I guess another lesson here is to read the 

WHOLE book when you're building airplanes...'cuz if you are maintaining 

airplanes too, you are going to need ALL the info sometime in the future. 





Bob, thanks again for the education.



-James

---

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