----- Original Message -----
From: "Joe"
Newsgroups: rec.radio.amateur.homebrew
Sent: Friday, April 16, 2004 7:15 PM
Subject: questions about 433MHZ modules

Hi, Joe -

I think the linear output is from the detector in the receiver while the
digital output is following an amplifier with AGC (automatic gain
control).
If so, then you may find that the linear output will decrease in
amplitude
with distance but the digital output will stay constant until the range
is
so great that the signal drops into the noise. Using the decoder on the
digital output eliminates the noise you see when the transmitter is off.

Sounds like a fun project.

John

Hi John,

Yes, it is fun. Looks like I will be learning about PLLs too. By the
decoder
do you mean the holtek?


Yes, that's what I meant.


I was not going to use the encoder and decoder,
since this is not a really critical application. I was planning on
generating a square wave with a 555 at the transmitter data pin and then
when the receiver detects it, take a picture. Yes, I think you are right
about the linear pin, because I noticed the magnitude of the received
signal
seemed to drop a little with distance, but the digital pin stayed strong
the
whole distance when I moved the transmitter from it. The linear pin seems
to
be much quieter tho.


Yes, it would be because of the lower gain. If you need the AGC associated
with the digital output, you might be able to use a phase detector IC on
that output to detect your 555's frequency. Maybe the phase detector output
would be quiet with no incoming carrier. On the other hand, you may not need
any more than what you've already tested. If you're happy with the distance
you get using the detector output, don't worry about it.


I still haven't worked on this yet today, so off I go to work on it some
more and maybe I can get a working circuit soon.


Good luck with it and let us know how it works when you're done.

John