[BC] Comparing the audio in the Big 50's

[Jim Tonne]

See added remark below.

On 6/20/2012 6:46 PM, Richard Fry wrote:

>RichardBJohnson wrote:

>>In fact, amplitude modulation has the capability of better fidelity than FM
>>because all of its bandwidth is available for audio.

>Those believing this about analog AM and FM broadcast systems might want to
>compare the published specs of AM transmitters to those of FM transmitters.

>The design/performance of their respective receive systems, co- and
>adjacent-channel interference, atmospheric and locally-generated radio noise
>also have large effects -- all of which favor FM.

>RF

FM simply trades off bandwidth for signal to noise ratio.

As Richard said, in practice the distortion levels of FM transmitters
can be lower than the distortion levels of AM transmitters.    But put
the receivers into the picture and things are evened out to some extent. 

It was an eye-opener for me when I was working on two of the "Quad"
FM systems that the FM receiver could so easily clobber the signal.
In particular, selectivity in the receiver was at odds with system
performance.  The GE system taxed the receiver less but would have
been a nightmare to put into practice.   The RCA system allowed a
modest variation to the standard receiver to receive the four channels.
It also precluded SCA as it existed at the time (on 67 kHz).

- JimT