kc8yqq wrote: ↑Fri Aug 30, 2019 8:52 am
Turkeytop wrote: ↑Thu Aug 29, 2019 9:29 pm
It was the only time I ever experienced AM stereo. Why did the broadcasting industry abandon that mode?
A few reasons I've heard:
1. AM stereo was replaced with IBOC
2. Format changed to talk, no need for stereo
3. Coverage is lessened
4. Equipment failed and don't want to fix/replace.....
Fallacy!
They are confusing AM stereo with FM stereo.
In FM stereo, the combination of the main baseband channel and the ultrasonic L-R subcarrier forces the station to halve the deviation on the main channel and the L-R DSSC subcarrier.
Fortunately, for the generous bandwidth given to an FM broadcast station, the loss of signal in the main channel is marginal.
FM stereo, however, greatly increases the receiver bandwidth - greatly increasing the noise level (usually in the form of white noise).
In AM stereo, the carrier is still fully modulated. An AM station operating in stereo is just as loud as a monaural AM station on a monaural receiver. A regular radio is unaffected by the quadrature component.
I will concede that AM stereo operation made co-channel interference more noticeable when co-channel interference was present. Many Class C stations should have operated in stereo only during daytime hours, or avoided it altogether.
AM stereo was far more expensive to install than FM stereo, and, with few stations using stereo, many stations saw no benefit in it.
However, the real death knell happened when all radio consolidated from thousands of owners to dozens. This made it easy for radio ownership groups to collude, and letting all that AM stereo gear to die saved money.
Sadly, The U.S. radio owners took Canadian radio into the hole. With NAFTA, Canada (where AM Stereo had been showing great potential) became unavailable because the USA didn't want it.
This also killed Canadian DAB, as the powerful NAB was able to squash it.