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FCC Emission Designators

R

RadioMan203

Doing a little research and trying to find what the AM broadcast emission designators were for pre NRSC-1 and post NRSC-1 stations. I know there was a change to designators at one point but I can't find the correct info. Any help is appreciated.

Possibly not clear, but I'm looking for the bandwidth designation which I hadn't found in my references. Thanks.
 
ScottJ said:
15K A3EG before, 10K A3EG after?
Click to expand...
15 kHz audio was allowed pre-NRSC, but beginning in the late '70s, AM audio processors from CRL and Orban (and probably others) employed low-pass filters to roll off the audio above 11 or 12 kHz and added pre-emphasis to the high frequencies, a practice which inspired the NRSC requirements.
 
This is what lead me to confusion. I was under the impression that audio processing for AM did not limit bandwidth until the 1980's implementation of NRSC-1.

I assume this was independent of receiver manufacturers starting to get cheap with the AM side of their products.

Also, is 10K the full bandwidth designator? I remember reading somewhere some of the bandwidth designations were changed and I thought there were additional characters (unless I'm confusing the emissions designator).
 
Bill DeFelice said:
Also, is 10K the full bandwidth designator? I remember reading somewhere some of the bandwidth designations were changed and I thought there were additional characters (unless I'm confusing the emissions designator).
Click to expand...

Yep, that's the way bandwidth is specified. The K (or M or G) acts as a decimal point, so if the bandwidth were 7.5 KHz we would write it as 7K5 A3EG.
 
Going one step further, does anybody know when the 15 kHz bandwidth designation was first made official? As far as I've ever been told, all through the golden age of AM radio (up until the late '70s), there was never any intentional restriction to the bandwidth of the audio being transmitted; it was simply a matter of whatever the station's program sources, audio chain, transmitter, and antenna system could achieve.

And in the 1930s and 1940s, there were experiments with "hi-fi AM" on frequencies above 1500 kHz, done by stations such as 1560 WQXR in New York. As the history section of WQXR's web site states, "In 1936, [John] Hogan partnered with Elliot Sanger and turned W2XR into WQXR, the first licensed high fidelity station in the U.S." Another source claims that WQXR retained 15 kHz sideband protection even after the "hi-fi AM" experiments ended and other stations began moving into the channels above 1500 kHz.
 
Way back when I've heard adjacent channel STLs and their programming show up in the side bands.
KPNW was using a composite STL with no filters and had an FM station with pilot in their sidebands. Their array bandwidth was the flattest I've seen. Ruler flat +- 40 KHz fed by an Ampliphase. They added 15 KHz l.p.f. to the audio to fix it.
 
Thanks for the assistance and clarification with my query.

I find the discussion of AM fidelity from back in the day interesting. I had several wideband tube receivers and remember just how good AM could sound. I then remember the first AM that I engineered and remember listening off the Belar and being totally amazed how AM could really sound.
 
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