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From The World Radio History Archives-FCC Broadcast Rules From 1964-The Origin Of Short Spaced Stations

If you look at Section 73.207 and Section 73.213, you'll see what the FM Rules were right after the Table of Allotments and Distance Separation Requirements. These left many station executives scratching their heads as to why many stations were now "Short Spaced". Section 73.213 was a very popular rule as originally written, as it told the stations they could be even more short spaced and increase facilities, often to maximum nondirectional for their Class. The FCC created Short Spacing by changing the rules, not the stations.

 
The AM portion is also interesting. The only table of assignments on AM was for Class II-A stations on some of the Class I-A clears, plus a couple of footnotes for WOI, WNYC and a couple other specific instances. (Two Class I-A on 770 to finally get KOB out of the FCC's hair, for instance.)
 
Interesting stuff there, Schroed -- thanks !

I'm a decidedly wet-between-the-ears and terminally non-technical DXer. But I was always intrigued by WALE 1400 Fall River and WBSM 1420 New Bedford Massachusetts.
And how short-spaced they've been, for decades.
Wiki says that graveyarder WALE signed on in 1948, omni. Regional WBSM signed on a year later, directional.
The two transmitting sites can't be much more than 12 miles apart.

And on Long Island, I worked for a while at WPAC 1580 Patchogue, a daytimer but with 10000 watts omni. The owners at the time were Adams-Getchall.
Co-0wned WAPC 1570 Riverhead was -- iIrc -- a 500 watt daytimer with two towers that sent its myriad programming attempts East. The two tower sites couldn't've been more than 18 miles apart as the cow flies.
 
For a while, WPAC 1580 and WAPC 1570 and their FMs were owned by Metrocom, which also owned some stations in Michigan. The Corporate VP of Programming was the late Bob Liggett, who bought Big Boy Restaurants and some stations in the Port Huron area before he died a few years ago. Rick Sklar worked at WPAC/WAPC early in his career. Beck Ross bought WGMZ from Metrocom, WKMF from Carroll Broadcasting (now owns stations in the Tawas Alpena area), and WPAC-FM 106.1, which became WBLI, the FM partner of WGLI 1290 Babylon, NY, later bought by the owners of WADO to go to 50 kW Day. My next door neighbor in Michigan did the sales inventory and accounting and an engineer friend of mine did the engineering inventory. It was WHRF-AM 1570 and FM 103.9 when they sold it. She was apparently offered a job in acquisitions and divestments by Beck Ross, but I don't think she wanted to travel. She was a no nonsense accountant, but a great humorous radio storyteller.
 
I was always intrigued by WALE 1400 Fall River and WBSM 1420 New Bedford Massachusetts.
And how short-spaced they've been, for decades.
Wiki says that graveyarder WALE signed on in 1948, omni. Regional WBSM signed on a year later, directional.
The two transmitting sites can't be much more than 12 miles apart.
The only thing I can think of is a lot of the ground conductivity in Massachusetts (and the rest of New England) is pretty awful. That, and if WBSM's pattrern is/was directional could be your answer to "how they got away with it".
 
It used to be that the 25 mV/m and 2 mV/m contours 20 kHz apart mutually couldn't overlap. Now it's 5 mV/m to 5 mV/m. That used to be a problem for upgrades under the old rules. WAMM/WFLT 1420 Flint was going to have to put up 9 towers to meet all the requirements to be 5000 watts, including WSAM 1400, then 250 watts in Saginaw, and soon 1000 watts Day. They never built it, and they probably have a better signal where they want it with 500 watts Day, 142 watts Night. It's in a conductivity sweet spot. They had a CP for 1000 watts Day in the late 1950s. WHK 1420 5000 watts in Cleveland was a Day and Night consideration, as was DWBRB 1430, a station once 25% owned by the late Gilda Radner.
 
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It used to be that the 25 mV/m and 2 mV/m contours 20 kHz apart mutually couldn't overlap. Now it's 5 mV/m to 5 mV/m. That used to be a problem for upgrades under the old rules. WAMM/WFLT 1420 Flint was going to have to put up 9 towers to meet all the requirements to be 5000 watts, including WSAM 1400, then 250 watts in Saginaw, and soon 1000 watts Day. They never built it, and they probably have a better signal where they want it with 500 watts Day, 142 watts Night. It's in a conductivity sweet spot. They had a CP for 1000 watts Day in the late 1960s. WHK 1420 5000 watts in Cleveland was a Day and Night consideration, as was DWBRB 1430, a station once 25% owned by the late Gilda Radner.
What fascinates me is the excessive separation of AMs in the US. I had two local stations in Quito, Ecuador that were on 570 and 590. They caused no problems between themselves, even though one was at the far south of the city and one to the far north.Yet even within a kilometer of either, the other was easily listenable on any kind of radio you could find.
 
What fascinates me is the excessive separation of AMs in the US. I had two local stations in Quito, Ecuador that were on 570 and 590. They caused no problems between themselves, even though one was at the far south of the city and one to the far north.Yet even within a kilometer of either, the other was easily listenable on any kind of radio you could find.
I'm curious to know the power of each. Should I assume they were single tower, omni?
 
Theoretically, since you only have a 5 mV/m City Grade signal requirement, and 30 kHz third adjacent overlap requirement, you could put stations in the same city 30 kHz apart. But most stations in larger cities with a lot of factory and business area noisemakers tried to put 25 mV/m over the whole city.

Looking at some applications with possible 30 kHz Canadian restrictions, like WTOR 770 to CFZM 740, there doesn't appear to have the restriction any more. The 15 mV/m contours are shown on some exhibits, and they don't overlap with WTOR and CFZM. I would think that the US Mexico agreement no longer includes a 30 kHz restriction either.
 
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