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[aprssig] Waveform (signal) on MX614 RXIN pin?

James Washer washer at trlp.com
Mon Jan 2 02:27:32 UTC 2006


Thanks for you help... found the problem.. I'd made a last minute change to my schematic, but not to my source code, so RXD was connected to an output pin on the MCU...

As Homer Simpson would say... "Doh!"

THANKS for all your help

On Sun, 01 Jan 2006 16:02:05 -0600
Ron Tonneson <ronton at southslope.net> wrote:

> Jim,
> 
> Take a look at the block diagram on page 3 of <http://atic.phys.lsu.edu/aces/Docs/Component%20Docs/mx614.pdf>.  Pin 5 is 
> the inverting input of an op-amp, pin 6 is it's output.  That is the reason why I see very little voltage on pin 5.
> 
> Yes, the signal on pin 6 is out of phase with the input due to the input being on the inverting input of the op-amp.
> 
> Ron - K0QVF
> 
> James Washer wrote:
> > One last question... do you have a dual trace scope? If so, are the signals on pins 5 and 6 out of phase by 180degrees? My belief is that the chip is (attempting to) scale the signal on pin 6 by feeding back a signal 180 out of phase. The resistor between 5/6 sets the bias, the cap controls the amplitude.. but I want to make sure this is the case.
> > 
> > thanks
> > 
> >  - jim 
> > 
> > On Sun, 01 Jan 2006 07:24:19 -0600
> > Ron Tonneson <ronton at southslope.net> wrote:
> 
> 
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