[AMRadio] Source Broadcast Xmtrs

[Paul Christensen]

> The FCC standard for broadcast AM has been 7.5KC and I doubt any
> commercial AM radios have ever gone beyond that.

That was the long-time standard for response and distortion measurements, 
going back to at least the mid 1950s.  I do not recall the FCC imposing a 
hard-line upper response limit until the initial NRSC-1 mask was developed 
in the late '80s.  But what many people do not know or recall is this 
performance section of the AM broadcast rules:

"In the event interference is caused to other stations by modulating 
frequencies in excess of 7500 cycles or spurious emissions, including radio 
frequency harmonics
and audio frequency harmonics outside the band plus or minus 7500 cycles of 
the authorized carrier frequency, the licensee or permittee shall install 
equipment
or make adjustments which limit the emissions to within this band or to such 
an extent above 7500 cycles as to reduce the interference to where it is no 
longer objectionable."

Unless the station (or FCC)  received reports of interference relating to 
wide bandwidth beyond +/- 7.5 kHz, AM broadcast transmitters were often 
modulated to double this amount if the bandwidth of the RF transmission 
system allowed it.

Paul, W9AC