Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uunet!lll-winken!tekbspa!optilink!elliott
From: elliott@optilink.UUCP (Paul Elliott x225)
Newsgroups: sci.electronics
Subject: Re: AM Radio
Summary: AM Broadcast Transmitter Modulator Design
Message-ID: <3044@optilink.UUCP>
Date: 29 Jan 90 17:34:15 GMT
References: <90026.012605TRM900@PSUVM.BITNET> <26374@cup.portal.com>
Distribution: usa
Organization: Optilink Corporation, Petaluma, CA
Lines: 28

In article <26374@cup.portal.com>, ISW@cup.portal.com (Isaac S Wingfield) writes:
> 
> If the transmitter is a standard plate-modulated rig, the 5 Hz will
> certainly saturate the modulation transformer, with possibly dire
> results; the 20kHz will spill, provided you can get it through that
> same transformer...
> 
> Modulation transformers are big, heavy, and *expensive*. Rest assured
> that the manufacturer didn't use any more iron than was necessary to
> get down to 50Hz, nor pay any more attention to distributed capacitance
> than necessary to get to 10kHz. [...]

Slightly off the subject of the original question (re: improving the
transmitted frequency response), What _is_ the current practice in AM
transmitter design?  I am familiar with the classic plate-modulation
methods, but many years ago studied other methods such as using two
unmodulated carrier sources, phase-modulating them, and combining them to
yield an AM signal.  This had the advantages of not needing all the iron
of the plate-modulation schemes, possibly better efficiency, and better
fidelity.

Can anyone educate me as to the current state of the art?


-- 
Paul M. Elliott      Optilink Corporation     (707) 795-9444
           {pyramid,pixar,tekbspa}!optilink!elliott
                  "The dog ate my disclaimer."