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1948 FM and TV Allotments

S

Schroedingers Cat

These were the Tables of Allotments for FM and TV in 1948.

See pages 602 to 605.


Note that all TV allotments were VHF, and it seems obvious now that there would be problems with cochannel station interference, especially across large bodies of water. This was addressed a few years later with some switching of particularly problematic cochannel allotments, UHF channels were added, and some markets were designated as UHF only, especially where they were were fairly close to large cities with a full allotment of channels.
 
The FCC was really in love with low-band VHF and was clueless as to propagation. Channels 2, 4 and 5 (and 9) in Chicago, Quad Cities and Des Moines? 7 and 9 in Chicago and Grand Rapids? 9 in Madison? Crazy. I know the 7 in GR got on air and was moved to 8 in the big shuffle of 1953.
 
If you read the rules at the same link, you will also see that the TV stations, and FM stations, were at much lower maximum ERP and HAAT, with some exceptions. That allowed more stations to be squeezed in, at least according to simpler propagation models. There soon was an association called Maximum Service Telecasters, headed by Lester W. Lindow, who was once a station General Manager in Michigan, which prevailed for many years in maximizing VHF service and interference rules.
 
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Schroedingers Cat said:
If you read the rules at the same link, you will also see that the TV stations, and FM stations, were at much lower maximum ERP and HAAT, with some exceptions. That allowed more stations to be squeezed in, at least according to simpler propagation models. There soon was an association called Maximum Service Telecasters, headed by Lester W. Lindow, who was once a station General Manager in Michigan, which prevailed for many years in maximizing VHF service and interference rules.
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I presumed as much for the ERP, and tall towers weren't a thing outside of NYC. But still. Chicago and Madison are 122 miles apart. You get to McHenry and the two channel 9s would have been hammering each other no matter what. (My godmother lived out there, and part of the fun of the trip as a kid was playing with the TV rotor to watch Chicago, Milwaukee and Rockford TV. Didn't know you could get Madison too, but from high in the dorm at Northern Illinois in DeKalb, Madison's UHFs were there even on rabbit ears.)
 
Detroit and Cleveland are about 90 miles apart, but I think the antenna farms are probably about 110 miles apart, but still, it's over Lake Erie. 2,4,5,7,9 for both. Asterisks indicate that the channel is either on the air or a construction permit. Cleveland ended up with 3,5,8, and Detroit with just 2,4,7. 9 went to Windsor.

WOOD-TV moved from 7 to 8 early on, because of WBKB 7. WOOD-TV moved to 7 digital, and that limited WLS-TV, which had to move to UHF. WKZO-TV 3 and WTMJ-TV 3 were on the same channel, and WTMJ-TV.
 
Too late to edit. WTMJ-TV moved to Channel 4.

At one time, VHF High Channels 7-13 were thought of negatively due to less bending of the signal over obstructions. All the stations that could tried to cram into Channels 2-6. Then ERP was raised to 316 kW for 7-13, receiver noise was reduced, and it became desirable. Of course, then UHF became the second class channels. Don't tell anybody that now the majority of stations are on UHF, and that's why they don't get out nearly as far. Channel 7 was where many late to the game network ABC affiliates went to, I guess because the propagation around obstructions was the best of the VHF High Channels.
 
Plus, legend has it, someone in the Army told ABC brass the Army was angling to grab the frequencies for low VHF. ABC would then have the first spot in major cities with a 1950s repack.
 
The 1953 shuffle saw WOOD 7 move to 8, but WTMJ moving from 3 to 4 triggered a domino effect. WBBM moved from 4 to 2, Zenith’s experimentation shoved to UHF. It allowed WHBF 4 in Rock Island interference-free air, 3 to open in Madison and Champaign, and the 2 assignment in Springfield went to St. Louis.
 
tvnut said:
The 1953 shuffle saw WOOD 7 move to 8, but WTMJ moving from 3 to 4 triggered a domino effect. WBBM moved from 4 to 2, Zenith’s experimentation shoved to UHF. It allowed WHBF 4 in Rock Island interference-free air, 3 to open in Madison and Champaign, and the 2 assignment in Springfield went to St. Louis.
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Zenith donated the KS2XBS facilities in 1953 to WTTW to start Channel 11, which went on the air a couple years later. They returned later in the 1960s on Channel 38 (WCFL-TV was a long-unbuilt CP which was sold to a religious broadcaster in 1976 and became WCFC).

The Channel 2 allocation disputed between Springfield, St. Louis, and Terre Haute was a different battle. It was too far away to make a difference in Chicago and points north. St. Louis and Milwaukee had their own allocation battles.
 
I've read about that Zenith donation to WTTW in various places, always a passing reference, so decided to find out what was donated.

Newspapers.com instead returned this news from the April 4, 1955 Chicago Tribune, CBS / WBBM donating $575,000 in transmitter and antenna equipment and the transmitter site in the Field Building to WTTW. CBS had maintained it as a spare since going on the air on Channel 2. Perhaps it was Zenith's old Channel 2 equipment, but CBS was the donor. Broadcasting's report in the April 18 issue (thanks, David Eduardo!) noted it included color-ready equipment and film cameras.
 
The first TV we had in the mid 1950s had a tuner that grouped the channels together that were supposed to be in local areas to theoretically minimize turning and wearing out the tuner. It went from 2,4,5,7,9,11,13,3,6,8,10,12, UHF. I assume it could have been fitted with a tuning slug that tuned one local UHF channel, or if it was just the same dial that was in a different model VHF UHF tuner. We had Channel 16 in our area for a few months, and people had two bay bow ties with reflector for it on their towers and rooftop antennas. I did see a VHF UHF tuner from the era that had an inner dial with 14-83 on a thumbwheel. It fascinated me from a young age. That antenna model has survived all these years, with the exception that the elements then were solid metal and not wire outlines or spokes. Just look at the Allied Catalogs from those years and you'll see them.
 
There were only 2 classes of FM in 1948, Class A (1 kW 250 feet HAAT) and Class B (generally 20 kW 500 feet HAAT). Both Class A and Class B were protected to the 1 mV/m (now usually called 60 dBu). Interference to Cochannels was 0.1 mV/m F(50,10). That means that with relatively flat terrain, cochannel Class Bs had to only be 100 miles apart for maximum facilities. First adjacent Class Bs had to only be 68.5 miles for full protection. That's why so many older stations are now considered to be (mutually) short spaced.

Many FM stations in smaller markets fairly close to larger markets, even Class Bs, were on AM towers, and only roughly 150 to 250 feet HAAT. Many Class Bs were also lower, some much lower, than 20 kW ERP, and could be squeezed still closer.
 
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I read years ago that the way the FCC came up with the height of the TV transmitting antenna & power out of antenna - it was values to give coverage based on the air miles between major east coast cities, like NYC to Philadelphia, Philadelphia to Baltimore, "kind of", etc.
Tweaked on, naturally pass the Rockies.

Kind of loose thinking I guess, but that is what I read many years back . . . in other words serve out to about 75 miles - give or take over flat terrain. The average air distance (about 80 miles) between these east coast cities.
 
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alok said:
I read years ago that the way the FCC came up with the height of the TV transmitting antenna & power out of antenna - it was values to give coverage based on the air miles between major east coast cities, like NYC to Philadelphia, Philadelphia to Baltimore, "kind of", etc.
Tweaked on, naturally pass the Rockies.

Kind of loose thinking I guess, but that is what I read many years back . . . in other wopastrds serve out to about 75 miles - give or take over flat terrain. The average air distance (about 80 miles) between these east coast cities.
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My experience with analog watching and DXing is 10 miles or so past the Grade B contour of a VHF TV station was about the limit, with an outdoor antenna, of reliable watchable service for the vast majority of the time. So that works out about the same as 75 miles. There were several VHF stations about 100 miles away, and they were intermittent, though you could see them for parts of the day nearly every day. Sometimes they were very strong under favorable tropospheric conditions.

You can find the old City Grade, Grade A, and Grade B contours in old TV Factbooks on worldradiohistory.com, and fccdata.com, on usually the oldest licensed facilty records of the older stations.
 
Schroedingers Cat said:
Now the majority of stations are on UHF, and that's why they don't get out nearly as far. Channel 7 was where many late to the game network ABC affiliates went to, I guess because the propagation around obstructions was the best of the VHF High Channels.
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Actually, what we thought we knew about VHF vs. UHF during analog days turned out to be reversed for digital. The VHF channels are the bad ones now. Several stations that originally planned to stay on their VHF channels begged the FCC to let them move to UHF after they realized how bad VHF is for digital signals. Perhaps ATSC 3 Next Gen will clear that up.

And you're right that ABC stations were a little late to the game and got assigned to Channel 7 (New York, Chicago, Detroit, Los Angeles and San Francisco), while the CBS and NBC stations mostly got Channels 2 through 6. I also remember reading somewhere that ABC thought several lower numbered channels would be claimed by the government, so the network believed 7 was a good place to be.

As stated above, in the 1960s VHF stations from 7 to 13 were allowed more power and became relatively even in signal strength with 2 to 6.
 
The hobbling of VHF is mainly due to setting the ERP maximum way too low. There is absolutely no way to get UHF signals much beyond hills and the horizon. It's due to the Laws of Physics, diffraction over obstructions and the horizon. In many areas, even those that are merely hilly, not mountainous, they need all kinds of fill in translators to fill in UHF terrain holes. As mentioned you used to be able to see most VHF stations 75 miles away. Except from mountaintop antenna farms like Mt. Wilson, you're not going to get UHFs nearly that far. Where I'm at, there's a full power 250 kW UHF, 15 miles away, over a relatively small range of hills, that you can only see during tropo events. There's a few 15 kW translators 20-25 miles away, LOS, across water, that do. We have some High VHFs 50 miles away that have had to increase ERP, one to 106 kW, to get over hills. A few others are 50-60 kW. They all duplicate on sub channels with LMA/Duopolies.

Most in Zone I are stuck at 30 kW or less. The reason WLS-TV moved is that it couldn't get enough ERP, and even with a deep null, to protect WOOD-TV, which moved from 8 back to 7. Another, WPBN-TV 7, was restricted to just 500 watts from Harrietta, due to WOOD-TV being so close. They put a 15 kW fill in translator at the old site, and moved to UHF much further North.

The excuse for ruining service areas is, "well, they nearly all have cable now, and in a few years, we'll all be available on the internet".
 
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Schroedingers Cat said:
The hobbling of VHF is mainly due to setting the ERP maximum way too low. There is absolutely no way to get UHF signals much beyond hills and the horizon.
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You are correct, I should have mentioned that I was referring to VHF signals 2-13 when the FCC did the "east coast city spacing signal thinking" - in the late 40's.

When we lived up near Yosemite National Park, I had a big antenna, there was a hill between me & SF (SF was about 120 air miles away) . . . I easily got the SF VHF's (analog days) but the UHF's were only in occasionally. Yes, there was noise (the average person would have not watched it) in the SF analog pictures.
Since most SF stations ended up on UHF after DTV, got nothing from SF after DTV except Channel 8 (KSBW)in Salinas (112 air miles), perfect pictures everyday from 8 . . . Channel 8 always had a great signal in its analog then digital days, view from me and Salinas was affected alittle by hills.
I always got Sacto V's & U's,(analog & DTV). I was about 85 air miles to Sacto TV but no hill between me & Sacto, was looking down at the Central Valley in that direction so Sacto was easy.
In analog days pictures from Sacto were perfect, no noise. DTV naturally perfect and clean.

But I did get Channel 2 KNOP North Platte, NE every E-skip season . . . perfect pictures & DTV. It's a hobby.

But your right, cable next steaming.

But still in metropolitan / suburban areas an antenna works great if it is installed correctly.
 
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