fm frequencies

[bobdavcav]

Ok here's an interesting question,
Notice that in LA and NYC, the radio dial is pretty straightforward, 92.3, 93.1, 93.9, 94.7, 95.5, and so on. However, how come you don't see a lot of this outside of the top 2 markets? We've seen some of this corrected over the years, but there are still many examples.
For example, there was a huge gap in Seattle where a 104.5 should have been that was finally filled in 2008. Why wasn't this originally allocated for the Seattle area, or why wasn't 102.9 licensed directly to the Seattle area with KZOK on 102.1? This may have something to do with the local channel restrictions since 100.7 was already on the air, and 102.3 was a local channel, but why wasn't that 100.5 from the beginning? Also, as a better example, it was 92.3, 93.7, and 94.7 in Portland for years until this was corrected in 2006 when 93.7 moved up to 93.9 in 2006 to make room for 93.1. Then of course we're seeing a major realignment in Salt Lake City right now. It seems to me as if frequency choices were sort of random until the band got crowded, then you had to take what was left over.

 

[KeithE4]

Ok here's an interesting question,
Notice that in LA and NYC, the radio dial is pretty straightforward, 92.3, 93.1, 93.9, 94.7, 95.5, and so on. However, how come you don't see a lot of this outside of the top 2 markets?

Top 3. Chicago's stations use these frequencies as well.

 

[bobdavcav]

I thought Chicago's 97.1 was a southern rimshot into the market? Yes they do use many of those frequencies as well (they do have a 106.7 as well) but if I understand right that's a rimshot as well, this time from the north.

 

[KeithE4]

I thought Chicago's 97.1 was a southern rimshot into the market? Yes they do use many of those frequencies as well (they do have a 106.7 as well) but if I understand right that's a rimshot as well, this time from the north.

WDRV 97.1 transmits from the John Hancock Center, and has for decades.

WPWX 92.3 is licensed to Hammond IN, but transmits from south suburban Calumet City IL. I don't know why they never relocated their transmitter to downtown Chicago, since I don't think there'd be any interference issues with co-channel stations in Peoria, Ft. Wayne, and Bloomington (Trafalgar), and NW Indiana would still be well-covered.

WPPN 106.7 is licensed to NW suburban Des Plaines, but transmits from even-farther-north Arlington Heights. The others in the 93.1, 93.9, 94.7... sequence all transmit from either the JHC or the Sears (I refuse to call it "Willis") Tower.

 

[bobdavcav]

Ok, didn't realize that. I always thought they were a rimshot of sorts since they have that simulcast on 96.9. I knew about the other ones. That's not really the point I was trying to make, though in some markets, like Spokane, 95.3, which seems like it should be a full market Spokane signal, is a rimshot serving mainly Sand Point, ID. I'm just not sure how these alotments came about.

 

[brettbutlerisok]

It seems to me as if frequency choices were sort of random until the band got crowded, then you had to take what was left over.

Ding Ding Ding, winner.

A station wanting to be licensed simply submitted a proposal, naturally on a frequency least likely to interfere with any other existing station anywhere near by. Most places weren't BIG like New York when radio started.

 

[davideduardo]

It seems to me as if frequency choices were sort of random until the band got crowded, then you had to take what was left over.

Not really. Unlike AM, where the biggest cities of the 20s got the best channels, FM in the post-war years was set up with a table of allocations where the FCC attempted to give all areas and cities channels in proportion to the population at the time. They promoted, of course, the policy of trying to spread stations so that every community of significance had a voice.

As all the original allocations were occupied, prospective licensees filed for amendments to the table of allocations and then filed for the new channel if it was allocated.

It was all pretty orderly until Docket 80-90 allowed "safe" upgrades in class and changes in COL without fear of cross-filings. At that point, the table of allocations was filled with many new channels, and many existing stations moved and upgraded. Many operators upgraded by petitioning for extensive changes in the allocations, some affecting ten or more stations.

Many believe that Docket 80-90 so wounded radio economically that it brought on consolidation as the only solution for the many stations losing money following 80-90-

 

[1L6E6VHF]

For all practical purposes, you can count Detroit In the "92.3 +.8....club". It had briefly been the #5 market, and sported every such channel. Though some have suburban COLS and others are licensed to Detroit whilst transmitting from just north of the Oakland County line, all serve Detroit well, and only two are "off-center". 93.9 was built by CKLW (directly on their Channel 9 TV tower right on the river, IIRC), obviously to serve Detroit. They had to move south in the 1980s.
102.7 came on in Mt. Clemens, and later found itself hemmed in by 102.9 Ann Arbor.

 

[bobdavcav]

Oh yeah, there are a lot more markets in that club, with the exception of 92.3 instead of 92.5, 92.7 instead of 92.9, and 100.3 instead of 100.5, San Francisco seems to be on that line as well. Now that I think about it, I would guess that when what is now KZOK came on the air in Seattle in 1964, they considered 102.3, but because that was a local channel at the time they went with the next one up, which was 102.5, where they still are today. Realligning that today would take some major shuffling, whether you're realigning 92.5 to 92.7, 93.3 to 93.5, 94.1 to 94.3 etc, or moving 102.5 to 102.1, moving 102.9 into the market, moving 101.5 to 101.3, moving 100.7 to 100.5, and moving 99.9 to 99.7. Neither is probably going to happen.

 

[MarioMania]

Why is the Seattle and San Francisco Market the same on the FM band? I'm wondering about that

 

[davideduardo]

Why is the Seattle and San Francisco Market the same on the FM band? I'm wondering about that

When the FM band was moved to the 88 to 107, the FCC created a table of allocations based on population where the larger cities got more channels and so on down to single-allocation markets.

The plan began by giving one of the several full allocations of stations to the largest markets. This meant that each of several groups of large cities all had the same "layout".

Over time, petitions to amend the table of allocations resulted in slight differences, particularly when later on channels were divided by class in the different regions.

Of course, a lot of that went to hell when Docket 80-90 dropped in a buncha' new allocations and made rural stations portable so they could move into larger markets.

 

[bobdavcav]

I guess that's just the way it came out. Milwaukee WI has a lot of the samr frequencies too.

 

[semoochie]

Why is the Seattle and San Francisco Market the same on the FM band? I'm wondering about that

They aren't. There are four primary Seattle frequencies not used in San Francisco: 92.5, 99.9, 101.5 and 102.5. In addition, 100.7 is a rimshot from San Raphael. There used to be even more of a difference. 104.5 is a recent entrant to Seattle and 103.7 moved from Class A 103.9 about 30 years ago or so. I didn't consider the non-commercial part of the band.

 

[MarioMania]

I know, Some are different..Most are the same like 106.1, 106.9, 107.7, 94.9, 95.7

Could 99.9 move to 99.7? I know there's KAAP 99.5 in Rock Island

 

[semoochie]

I know, Some are different..Most are the same like 106.1, 106.9, 107.7, 94.9, 95.7

Could 99.9 move to 99.7? I know there's KAAP 99.5 in Rock Island

If you start at 92.3 and the next station is 93.1 then 93.9 and so on OR you start with 92.5 to 93.3 to 94.1 etc., you can get all through the dial and still have full power stations on every frequency. If you start anywhere else and keep the same spacing, you run into a dedicated Class A frequency. At least, this is the way it was when they set up the allocations table in the first place. Those Class A stations used to be the FM equivalent of 1230, 1240 etc. Here they are: 92.1, 92.7, 93.5, 94.3, 95.3, 95.9, 96.7, 97.7, 98.3, 99.3, 100.1, 100.9, 101.7, 102.3, 103.1, 103.9, 104.9, 105.5, 106.3 & 107.1

 

[bobdavcav]

The am band makes sense to have dedicated local, regional, and clear channels, but what was the logic behind it on fm?

 

[davideduardo]

The am band makes sense to have dedicated local, regional, and clear channels, but what was the logic behind it on fm?

Larger cities got more B's or C's, with some being put at the larger cities in more rural areas. Suburbs and smaller cities got A's.

Amendments to the Table of Allocations modified this considerably from the 40's to the 80's. Docket 80-90 destroyed it beyond recognition around 1990.

Go to http://www.americanradiohistory.com/Archive-BC-YB/Broadcasting-1948-Yearbook-Page-Range-Guide.htm and click on "FM Stations and Allocation Table" to see how it was set up originally. There is an element of geographical/population based logic there.

 

[K.M. Richards]

The am band makes sense to have dedicated local, regional, and clear channels, but what was the logic behind it on fm?

The general idea was to have as many full-power stations as possible in a metropolitan area, which is why in those major markets we've already discussed, those allocations start at 92.3 and then skip three channels to land on the fourth, 800MHz away. So ... 92.3, 93.1, 93.9, 94.7, 95.5, 96.3, all the way up to 107.5 ... and those were the higher-power allocations when the table was first set up (as has already been pointed out, there is no longer any rhyme or reason, and signals are fit in wherever they can be).

Now, offset to the middle of those three skipped channels, and you had the lower-power allocations which were alloted to smaller communities of license within the metropolitan area. Using Los Angeles as an example:
92.7 - Thousand Oaks, just over the L.A. border with Ventura County
93.5 - Redondo Beach, in the South Bay region of Los Angeles County
94.3 - San Fernando, in the Valley of the same name
95.1 - assigned as higher-power regional stations in Ventura and San Bernardino
95.9 - Anaheim, in Orange County
96.7 - Santa Ana, also in Orange County
97.5 - higher-power stations in Riverside and Santa Barbara
98.3 - West Covina, in the San Gabriel Valley region of L.A. County
99.1 - higher-power in Riverside
99.9 - higher-power in Santa Barbara and Riverside
100.7 - higher-power in Ventura and San Diego
101.5 - higher-power in San Diego
102.3 - Compton, inland from the South Bay several miles
103.1 - Santa Monica (L.A. County) and Newport Beach (Orange County)
103.9 - Inglewood, near LAX
104.7 - higher-power in Oxnard
105.5 - Long Beach
106.3 - Santa Ana in Orange County, San Fernando
107.1 - Sierra Madre
107.9 - San Clemente, about as far down the I-5 you can go without traversing the Orange/San Diego county line

This is pretty much how it was originally set up; there have been changes of community, additions of lower-power allocation, and moves over the years ... for example, 106.3 did operate for a while but after it went silent the allocation was moved to Lancaster, in the Antelope Valley region of L.A. County.

What this spacing accomplished, given the less-sensitive frequency rejection circuits in FM receivers back then, was ensure full-market coverage on the high-power stations but also allow local community service on every other channel, which would be tunable clearly in a smaller radius.

Of course, as David has pointed out, the 80-90 expansion, plus greater selectivity in FM tuners, has resulted in just about every station trying to be a full-market one.

Hope that helped answer the question without causing your eyes to glaze over.

 

[MarioMania]

Without making a thread about it, I just ask on her

When I hear about Station on FM or AM..Some people talk about mV/Contor whatever it is

What does it mean anyways, I just listen to the radio as a hobby and DX..I do want to know what stuff is

 

[K.M. Richards]

When I hear about Station on FM or AM..Some people talk about mV/Contor whatever it is

Put simply, it is a measurement of the signal strength. When plotted in a map, it indicates where a station will be received clearly as a local signal, etc. Stations' primary signal contours are legally protected from interference by other licensed stations.

If I try to explain it better, I'll have to start using technical terms which I don't think you want, Mario.