[BC] AM Stereo

[Craig Bowman]

Kyle,

AM, before NRSC was technically superior from an audio standpoint.  
20kHz audio was the standard for AM.  The problem is reception.  
Receiver manufacturers have been narrowing the bandwidth of the radios 
since the 70's.  IC's killed AM rather than FM.  If you ever listened to 
a well engineered AM on a modulation monitor feed you would know the 
difference.  I once did a test using the accounting people at one of my 
stations.  We were simulcasting Christmas music on the AM and FM.  Using 
a Carver receiver (which was not NRSC compliant) I A/B the two 
stations.  Each person picked the AM as better sounding (using JBL-4412 
speakers and a Crown D-150) than the FM.  I had to prove to them that it 
was the AM before they would believe me.  Yes, the AM was stereo.

Craig Bowman
Bowman Engineering
Local HDTV, Inc.
989-277-8835

On 11/24/2010 1:53 AM, Kyle Magrill wrote:
> That's the point.  It's fidelity not the number of channels that matters.
> If AM sounded as good as FM, it could comptete, even if it was mono.
>
> Now, as to the issue of good sounding AM receivers, I agree that it was
> possible to build a good one at any point along the broadcast timeline.
> My point was that it cost more to do that which is bad if the market trend
> is to make cheaper radios.
>
> In fact, simple crystal sets are quite hi-fi.   But they lack both sensitivity
> and selectivity.  Getting good audio performance while keeping the sensitivity
> and selectivity added cost.   Starting with the first pocket transistor radios of
> the 1950s, the push was on to build cheaper radios, not bettter ones.   When
> FM became a desirable addition to radios, it could be added cheaply and still
> sound good, whereas AM used tight IFs to get the sensitivity and selectivity up.
> If the IFs are loose, then more stages are required leading to higher manufacturing
> costs.
>
> Today, the story could be different.  The advent of DSP based radios means
> stuff  that was expensive a few years ago can be done cheaply and better in
> software, but again, the genie has, long ago, escaped the bottle.