[AMRadio] Only function of carrier

[Gary Schafer]

I like to think of the detector as a mixer. It recombines the three RF
signals, upper side band, carrier and lower side band. The heterodyne action
converts those RF signals down to audio. The carrier is filtered out and not
used once the conversion is done. 
The two side bands add together in the detector to produce twice the audio
voltage that one would produce.

The carrier is needed in the demodulation process as it has a specific phase
relationship with each side band. But once the side bands are back to audio
the carrier is done with its job other than of course using its rectified DC
to control the agc in the receiver.

73
Gary  K4FMX

> -----Original Message-----
> From: amradio-bounces at mailman.qth.net [mailto:amradio-
> bounces at mailman.qth.net] On Behalf Of CL in NC
> Sent: Monday, April 25, 2011 1:11 PM
> To: amradio at mailman.qth.net
> Subject: [AMRadio] Only function of carrier
> 
> The only function of carrier is to operate the detector circuit.  The
> time constant is long on the  output of the detector at the IF freq, the
> carrier converted down to the IF freq. charges this RC circuit up.  As
> the upper sideband signal, being a higher freq,  adds to the output of
> the detector as its higher IF freq.  switches the circuit on and off
> generating more charge, the LSB signal subtracts from this voltage as
> it's lower freq allows the circuit to discharge.  The output is a
> waveform that represents the transmitted audio and is sent to the audio
> amp.  100% modulation on  any RF carrier level is the best you can get
> for fidelity, but maybe not communication punch through ability.
> 
> Now, for the folks that think base response is the be all end all for
> AM,  weak signals are impossible to copy when you are all base, no
> highs.  There are a lot of signals I hear with my R390A, Hammer 170A and
> R4C that could be copyable if only they had full range of audio, but for
> some reason, their owners bow to the god of low freq range audio.
> 
> Charlie, W4MEC in NC
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