Why Are LA and SF FM Stations Mostly Over-Powered?

[Gregg]

Most of California is Class B territory for FM stations. It joins most of the Northeast, Mid-Atlantic, Great Lakes and Carribean regions, where FM stations are permitted a maximum of 50,000 watts at 500 feet. (Actually that height has been changed to reflect meters instead of feet, but that was the max before the metric conversion.)

Yet nearly all FM station in the LA and San Francisco markets run with much more power than that. In fact, many stations in LA and San Francisco exceed the maximum power for Class C stations, apx. 100 kw at 1500 feet, common in the rest of the country.

What's also odd is that in California, this is not repeated in other markets. In San Diego, for instance, only 94.1 runs at 77,000 watts. (They had been at 100 kw before they went on a taller tower.) All the other stations in San Diego stay within Class B limits. Same for San Jose, where only 100.3 is overpowered. Monterey-Salinas have a couple of overpowered FMs (96.9 and 102.5). Riverside-San Bernadino have a couple (97.5 and 99.9). Ventura has 100.7, Fresno has 93.7, Sacramento has 100.5 and I don't think Bakersfield, Palm Springs or El Centro have any.

Santa Barbara's 103.3 wins the prize as perhaps the most overpowered FM in country, 105,000 watts on a tower nearly 3000 feet above average terrain. But that's it for Santa Barbara.

Meanwhile, LA's over-powered stations include
90.7 KPFK
91.5 KUSC
92.3 KHHT
93.1 KCBS-FM
93.9 KXOS
94.7 KTWV
95.5 KLOS
97.1 KAMP
98.7 KYSR
99.5 KKLA-FM
100.3 KSWD
101.1 KRTH
101.9 KSCA
102.7 KIIS
103.5 KOST
104.3 KBIG
105.1 KKGO
105.9 KPWR
107.5 KLVE

Maybe I should also ask what's wrong with 96.3 KXOL-FM, 97.9 KLAX and 106.9 KROQ? They're the only Class B stations in the LA market that stayed within the power limits. Were their owners asleep while everyone else was putting high-powered transmitters at the top of Mt. Wilson?

 

[cyberdad]

I stand to be corrected....at least on possible individual station details...but your quick answer: Grandfathered.

 

[Schroedingers Cat]

They are no doubt grandfathered. But the reason they were allowed superpower is because California didn't used to be in Zone I, or Zone I-A, or whatever the FCC calls it. Neither was Michigan, Ohio, or Illinois, or other states in the Midwest where grandfathered stations exist or did until fairly recently. I seem to remember WEAW-FM being 180000 watts from the original WEAW 1330 tower(s) near Evanston, and WMBI-FM being 100000 watts, and WNOB...WENZ being 70000 watts, and some other superpower stations near Dayton fairly recently. Those areas were added to Zone I later. David, our resident Broadcasting archivist and historian, now has the 1960 NAB Engineering Handbook on his website, and that has somewhat excerpted rules that were present until the 1962-1964 era. I don't remember superpower stations going on the air past 1962, and the Table of Allotments came out around 1964 with a lot of the newer rules. I will look at this later on davidgleason.com. Many of the stations in the Midwest have reduced power or gone to Class B maximum over the years.

I doubt that those stations on Mt. Wilson could put a 70 dBu signal over all of Los Angeles with a 50 kW/150 meter facility, as the 70 dBu only goes out a little more than 20 miles with a reference Class B, unless it was on the side of a mountain, where the HAAT away from the side of the mountain could be more than 150 meters and below 0 meters toward the mountain range.

 

[pianoplayer88key]

That KVYB 103.3 in Santa Barbara really gets out. I can usually fairly reliably hear it near a 900-foot-elevation hilltop about 3/4 mi NW of my house, 211 miles from their transmitter.

Speaking of super-powered FM, I was wondering ...
what transmitter output power, antenna efficiency (in mV/m @ 1 km for 1 kW in the horizontal plane) and HAAT would be required ...
... to have 100% reliable HD reception on a pocket-sized Coby or Insignia HD radio ...
... out to the distance, over an all-saltwater path, that a longwave SSB broadcast station on 153 kHz transmitting 2 megawatts into an antenna with at least 512 mV/m @ 1 km for 1 kW efficiency (preferably 1024 mV/m, or even 3200 mV/m or whatever is the best efficiency that exists for FM and TV stations) ...
... would be barely identifiable by an expert seasoned DXer in an ultra-quiet environment, using a communications receiver with 1.8 kHz IF bandwidth and a beverage antenna?

 

[Schroedingers Cat]

Generally, salt water or other conductivity is not figured into FM and TV propagation curves, although Longley Rice does have a place for it to be figured into the calculation.

 

[pianoplayer88key]

That's not QUITE what I meant I was wondering (see my previous post for more specific criteria) what it'd take for an FM (or TV) station to replicate the coverage a mega-power longwave station has when it (the LW station) enjoys a saltwater path.

 

[rbrucecarter5]

102.7 KIIS

They need all the power they can get - the mountains are a big headache for them. Not only are they severely clobbered on back sides of mountains, there is even a first adjacent nearby because they are so severely attenuated.

 

[rfry]

Speaking of super-powered FM, I was wondering ...
what transmitter output power, antenna efficiency (in mV/m @ 1 km for 1 kW in the horizontal plane) and HAAT would be required ...
... to have 100% reliable HD reception on a pocket-sized Coby or Insignia HD radio ...
... out to the distance, over an all-saltwater path, that a longwave SSB broadcast station on 153 kHz transmitting 2 megawatts etc etc

A "100% reliable," v-pol groundwave field from a transmit system much above the 153 kHz frequency and 2 MW radiated power quoted above becomes increasingly unlikely with higher frequencies -- even with higher radiated powers, the most sensitive receive systems, and the hopes of their operators.

Reception of point-to-point VHF FM signals at the surface of the earth, and occurring a significant distance beyond the range shown for the HAAT and ERP shown by the FCC F(50,50) FM propagation curves will be related to reflected sky waves, and will occur with MUCH less than 100% reliability.

 

[w9wi]

The bottom line is, that until the framework of the current FM rules went into place in the early 1960s (1964?), there was no power limit for most FM stations.

There was a theoretical limit of 20kw/500', but the Commission entertained requests for waivers from stations outside the Northeast and would regularly grant those waivers. In the Midwest, permits for powers of 200kw or more were not particularly unusual. Though I should note, many of these ultra high power stations were never built, at least not at their full power.

 

[rfry]

Just to note that it is both theoretically and practically impossible for a VHF station to have a "100% Coverage" groundwave field ~equivalent to that of a v-pol transmit system radiating 2 MW at 153 kHz.

 

[ftballfan]

Outside of LA and SF, I think Detroit, Grand Rapids, and Pittsburgh would have the most grandfathered stations. NYC and Philly have zero and DC and Chicago only have one apiece.

 

[gar hi]

They need all the power they can get - the mountains are a big headache for them. Not only are they severely clobbered on back sides of mountains, there is even a first adjacent nearby because they are so severely attenuated.

That was my first guess too.

That KVYB 103.3 in Santa Barbara really gets out. I can usually fairly reliably hear it near a 900-foot-elevation hilltop about 3/4 mi NW of my house, 211 miles from their transmitter.

That has to be so awesome to be able to hear a station at that distance without tropo required.

93.3 FLZ here in Tampa seems to really get out there. Their power is almost 100 kw and their tower is about 1,500 ft.

They are heard well past Orlando even during non tropo conditions.

I've never heard any station like that in the northeast.

 

[K6JHU]

FM station on Mt. Washington.

 

[Schroedingers Cat]

Michigan By Frequency (Detroit and Grand Rapids COL not shown)

90.5 WKAR-FM 85000 East Lansing (once 125000)
91.7 WUOM 93000 Ann Arbor (once 230000)
93.7 WBCT 320000 (once 500000, authorized 550000)
95.5 WKQI 100000 (once 165000)
101.1 WRIF 27000 (27200) (Under older rules about two times permitted ERP at HAAT)
102.5 WIOG 86000 Bay City (once 90000, though can't find in David's site)
104.1 WVGR 96000 (once 108000)
104.3 WOMC 190000 (once 215000)
105.7 WSRW 265000
106.7 WDTW 61000 (61125)

Former grandfathered facilities.

99.1 WFMK 116000 East Lansing
100.7 WITL 55000 Lansing (was a lot more, on Olds/MNB/Boji Tower)
101.9 WDET 79000
103.5 WMUZ 115000

 

[Schroedingers Cat]

I believe WFMT Chicago and possibly another one or two have more power than currently permitted at their HAAT, in addition to WMBI-FM.

It gets confusing with the two multiplexed sites and the old and new ERP levels authorized by the FCC for stations above the reference height, which also changed from 152 meters to 150 meters, plus a directional here and there that went nondirectional. I don't believe the ERP decreases until 152 meters in fact. There used to be a parametric graph that showed a given log log decrease above the reference height. The Class Bs didn't like it and the NAB forced the FCC's hand to make it contour distance based, which allows rounding down from 0.4 km over reference contour distance.

 

[w9wi]

I believe WFMT Chicago and possibly another one or two have more power than currently permitted at their HAAT, in addition to WMBI-FM.

Yes, WFMT is grandfathered. Distance to the 54dBu contour is 69.4km, vs. something just shy of 66km for the other full B's in Chicago. For what it's worth, this is almost as good as WMBI's 100kw signal -- because WMBI's tower is pretty low.

105.1 was once overpowered, 135kw IIRC. They aren't anymore.

In southern Wisconsin, consider WOLX 94.9 Baraboo/Madison; WERN 88.7 Madison; and WHAD 90.7 Delafield/Milwaukee. 54dBu on these stations is 83.36km, 76.56km, and 74.88km respectively. WOLX is an interesting case: the transmitter is only four miles south of the zone boundary -- if it were four miles further north, it would be in Zone II and would be an ungrandfathered Class C-something (C1, I suppose) station...

 

[Schroedingers Cat]

Usually those near 43.5 latitude are also short spaced, and by the time you find a fully spaced site for C1, it's so far away that it is not worth it. There might be a few that might benefit if the move was small from Class B to Class C2 if it was fully spaced as a C2. Sometimes Class C1s are so far out that they would benefit by being C2 or even C3 in some cases. Usually directional is a big problem, as Bob On The Job has noted. You could be closer with 100 kW directional, but the actual ERP is substantially less than the licensed envelope, and it is weaker than if you hadn't moved or "upgraded" at all. It all depends on actual ERP in specific directions toward the center or centers of population. I've seen 6 kW directional Class As and even 25 kW B1s and C3s that are disappointing as directional and further out. Usually if you can have 50 kW to 100 kW omni and not a ridiculously low HAAT, that's best.

 

[ftballfan]

In regards to WOLX being just four miles south of the zone boundary, I've seen at least one source refer to it as a Class C1 station. In Michigan, there are four stations just north of the zone boundary:
90.3 - WBLV Twin Lake (100kW/185m) (Class C1)
94.5 - WCEN Hemlock (100kW/299m) (Class C1) [formerly licensed to Mt. Pleasant]
96.1 - WHNN Bay City (100kW/311m) (Class C0) [Same COL as grandfathered Class B WIOG]
99.7 - WUGN Midland (100kW/304m) (Class C)
94.5 and 96.1 also have grandfathered short spacing involved.
Honorable mention to now-WHTS Coopersville, as back when it was WCXT Hart, it was 100kW within 15 miles of the zone boundary before it downgraded to C2 from Hart and later moved into Grand Rapids and became Class B

 

[Schroedingers Cat]

MacDonald Broadcasting, now MacDonald Garber, moved WMBN-FM/WLXT from Class A on 96.7 South of Petoskey to Class C on 96.3 from near Good Hart/Cross Village. They soon downgraded to Class C1 from SE of Petoskey, a much more reliable and accessible site for maintenance. They were going to use the Good Hart/Cross Village tower to move WKCQ northeast of Saginaw near WIOG as a B or C2, right near 43.5 latitude. Problems with short spaced WJLB couldn't be resolved, and they used part of the tower to stay on M-46 and increase height with 50 kW from 340 to 492 feet. I think WJLB increased height from 400 to 500 feet also.

 

[cyberdad]

In southern Wisconsin, consider WOLX 94.9 Baraboo/Madison; WERN 88.7 Madison; and WHAD 90.7 Delafield/Milwaukee. 54dBu on these stations is 83.36km, 76.56km, and 74.88km respectively. WOLX is an interesting case: the transmitter is only four miles south of the zone boundary -- if it were four miles further north, it would be in Zone II and would be an ungrandfathered Class C-something (C1, I suppose) station...

The result for WOLX is that they have a fairly competitive signal throughout most of the Madison metro instead of being just another rimshot.