From: paulm@storcon (Paul Moreau)
Subject: Re: AM vs FM AGAIN? - Have Mercy
Organization: Storage Concepts, Inc.
Date: Wed, 9 Sep 1992 14:08:10 GMT


In article <1992Sep7.235638.7688@ccu.umanitoba.ca>, umteghts@ccu.umanitoba.ca (david teghtsoonian) writes:
|> In <1992Sep5.042114.3993@nntpd.lkg.dec.com> fisher@kay.enet.dec.com (kay::fisher) writes:
|> 
|> >>   Dual conversion on an AM?   I thought that dual conversion was impossible/
|> >>   useless on an AM receiver because of the method of detecting an AM signal.
|> >>   Besides,   I've yet to see an AM receiver that had 'Dual Conversion' on it.
|> >>
|> >>-- 
|> >>          _____________________________________________________________
|> >>          -                *                      _______   _~;       -
|> >>          -            Paul Moreau               |       =_= /        -
|> >>          -    Sr. Diagnostics Software Eng.     \   USA    /         -
|> >>          -         Irvine, California      --->  *-_  ___ /          -
|> >>          -     UUCP: ..!uunet!storcon!paulm         \/   \\          -
|> >>          _____________________________________________________________
|> 
|> >Well - I didn't want to answer till I was sure.
|> >Check out Model Aviation October 1992 issue page 160.
|> >The add for Kraft Midwest Inc. shows a dual conversion AM receiver.
|> 
|> >Bye          --+--
|> >Kay R. Fisher  |
|> >---------------O---------------
|> >################################################################################
|> 
|> 
|>    Actually, dual or single conversion superheterodyne receivers work equally
|> well using AM, FM, PCM or just about any other modulation technique. Dual
|> conversion, without getting too technical, takes place BEFORE the demodulation
|> stage of the receiver, so the modulation scheme used is irrelevant. Dual
|> conversion makes the receiver less susceptable to interference from other
|> signals as well as reducing the spurious emissions (interference to other
|> people's receivers) produced by your receiver. The modulation scheme used
|> also has an impact on the receiver's susceptabilty to interference. AM is
|> naturally more susceptable to interference than FM or PCM and probabley
|> stands to gain the most from using a dual conversion receiver.
|> 
|> -Curt

   Thank you for clearing that up for me.  I stand corrected.

   BTW:  PCM can use either FM or AM modulation.   Both AM and the standard FM
         use PPM.   Pulse Code Modulation and Pulse Proportional Modulation.
         (or is that Pulse Position Modulation)?

         Most PCM's use FM signal modulation be cause of the inherent noise
         immunity.   If it used AM and was in a noisy environment then it
         would spend more time in failsafe or hold than operating.
-- 
          _____________________________________________________________
          -                *                      _______   _~;       -
          -            Paul Moreau               |       =_= /        -
          -    Sr. Diagnostics Software Eng.     \   USA    /         -
          -         Irvine, California      --->  *-_  ___ /          -
          -     UUCP: ..!uunet!storcon!paulm         \/   \\          -
          _____________________________________________________________

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