Saturday, July 31, 2010

Mediumwave Oddities - Geography

Think you know mediumwave? Are you good at geography? Do you like statistics?

Let's look at the geographical oddities of the mediumwave band for the United States. Information has been gleaned from current FCC records, and includes only US-licensed stations. 4784 licensed stations were used to compile these statistics from the FCC database dated July 14, 2010.


Did you know that 21% of all US-licensed AM stations are east of Florida? This one surprised me.

Which US station is the farthest east? Remember, east goes all the way to the International Date Line.

If you guessed a station in Maine, you would be wrong by a great margin. The farthest US station in the eastern hemisphere is KCNM-1080 (5KW), Saipan, Northern Marianas at 145.714E longitude. Next would be KGUM-567 (10KW), in Agana, Guam at 144.759E longitude. Three other stations in Guam are #3, #4, and #5 farthest east in longitude, west of the International Date Line.

So, how about the continental US? Are we there yet?

Think Carribbean. WSTX-970 (5KW), in Christiansted, US Virgin Islands is next farthest east at 64.693W longitude, and the most eastern US station in the western hemisphere. Five other US Virgin Islands stations are next.

Next comes a slew of stations in Puerto Rico, in fact 75 of them. The farthest east in Puerto Rico is WMDD-1480 (5KW), at 65.64W longitude.

Now we finally come to the continental US. The most easterly station in the continental US is WXME-780 (5KW), Monticello, Maine at 67.817W longitude. However, there is an application on file for a "NEW" AM station in Calais, Maine at 67.266W longitude which will take the title if it ever goes on the air.

But what about Florida, you ask?

Florida is not even close in the running. WWRF-1380 (1KW), Lake Worth, Florida at 80.072W longitude is the station farthest east in Florida. Astonishingly, there are 921 stations up and down the east coast of the continental US which are farther east than Florida's WWRF-1380, and 1007 stations farther east in total, clear to the International Date Line, all licensed to the US via the FCC.

Amazingly, 1007 stations (21%) of 4784 licensed FCC stations are east of Florida.

Which is the most easterly NPR (National Public Radio) station?

WFPB-1170 (1KW) Orleans, Massachusetts at 70.01W longitude.

Most of us know that "K" stations are west of the Mississippi, and "W" stations are east of the Mississippi, except for a few exceptions, like KDKA-1020 in Pittsburgh, PA and KYW-1060 in Philadelphia, PA and WOAI-1200 in San Antonio, Texas.

Which is the farthest east "K" station, east of the Mississippi River?

That would be KCNM-1080 (5KW), Saipan, Northern Marianas at 145.714E longitude. It is 7788 miles east of Wasington, DC where the FCC is located, and most definitely east of the Mississippi River. The most easterly "K" station in the lower 48 states is KYW-1060 (50KW), Philadelphia, Pennsylvania at 75.248W longitude.


Which US station is the farthest west?

We have two winners. KJAL-585 (5KW) Tafuna, American Samoa at 170.776W longitude and WVUV-648 (10KW), Leone, American Samoa at 170.776W longitude, both in the South Pacific and licensed by the FCC, some 7035 miles west of Washington, DC. They transmit from the same location.

Which is the most westerly station in the lower 48 states?

KBIS-1490 (1KW), Forks, Washington at 124.388W longitude. There are 72 stations farther west of this, all in Alaska or the Pacific Ocean.

Which has more AM stations, Hawaii or Alaska?

Hawaii has 30; Alaska has 40. Alaska is the winner.

Which is the most westerly Alaskan station?

KICY-850 (50KW), Nome, Alaska at 165.314W longitude. There are a total of 6 Alaskan stations that are farther west than the most westerly Hawaiian station, KUAI-720 (5KW), on the island of Kuai.

Which is the most westerly NPR station?

KOTZ-720 (10KW), Kotzebue, Alaska at 162.568W longitude.

Which is the farthest west "W" station, west of the Mississippi River?

The prize goes to WVUV-648 (10KW), Leone, American Samoa at 170.776W longitude. So much for WOAI-1200 in San Antonio, Texas! WOAI-1200 is the most westerly in the lower 48 states.


Which US station is the farthest north?

KBRW-680 (10KW), Barrow, Alaska at 71.256N latitude.

Which NPR station is the farthest north?

Again, KBRW-680 (10KW), Barrow, Alaska at 71.256N latitude.

How about the continental US? Which station is the farthest north?

We have a tie. KVRI-1600 (50KW), Blaine, Washington at 48.954N latitude and KARI-550 (5KW), Blaine, Washington at 48.954N latitude.

How come a station in Maine isn't the farthest north?

The most northern station in Maine is WFST-600 (5KW), Caribou, Maine at 46.886N latitude. 180 stations are farther north than WFST-600, and all are scattered from Minnesota all the way to Alaska.

The geographical center of the lower 48 states lies outside of Lebanon, Kansas, in the middle of what used to be a hog farm.

Are there more stations to the north or to the south of this location?

There are 1814 stations to the north and 2970 stations to the south of Lebanon, Kansas.


Which US station is the farthest south? Think outside of the continental US.

Another tie. KJAL-585 (5KW) Tafuna, American Samoa at 14.357S latitude and WVUV-648 (10KW), Leone, American Samoa at 14.357S latitude. Coincidentally, these two stations are not only the farthest south, but also the farthest west.

Which is the most southerly station in the continental US?

WKIZ-1500 (250W), Key West, Florida at 24.567N latitude. The Florida Keys have 3 stations - 2 in Key West, and 1 in Marathon Key.

How about Texas? It's pretty far south.

The most southerly station in Texas is KVNS-1700 (8.8KW), Brownsville, Texas at 25.949N latitude.

And California?

That would be KURS-1040 (360W), San Diego, California at 32.694N latitude. Texas is much farther south than California.

How many stations are south of the continental US?

There are 118 stations south of the continental US, that is, south of Key West, Florida. All are in the Pacific or Caribbean.

The Mississippi River runs north and south through the country, dividing the US east to west approximately at St. Louis, Missouri (90.18W longitude).

Are there more stations to the east or to the west of St. Louis?

There are 1990 stations west of St. Louis and 2794 stations east of St. Louis. The majority of stations are to the east of St. Louis, in fact, 71% of them.


How about some IBOC stats?

There are 293 licensed IBOC stations. Two are silent at the moment.

The most westerly IBOC station is KOTZ-720 (10KW), Kotzebue, Alaska at 162.568W longitude. It is also the most northerly IBOC station and the most westerly NPR station.

The most easterly IBOC station is WIPR-940 (10KW), San Juan, Puerto Rico at 66.141W longitude. It is also the most southerly IBOC station.

There are 128 IBOC stations west of the Mississippi River. There are 165 IBOC stations east of the Mississippi River.

Which state has the most IBOC stations?

California wins with 32. Runner up is Florida with 25, followed by Colorado at 17. New York has 16, and both Texas and Ohio have 15 each.

Which state has the fewest IBOC stations?

Several are tied. Kentucky, Mississippi, North Dakota, Nebraska, and South Carolina have 1 each. Arkansas, Delaware, Idaho, Louisiana, Maine, Montana, New Mexico, and Nevada have 2 each.

Which state has the most IBOC NPR stations?

Surprise! Alaska wins with 6. Alaska also has the most NPR stations overall at 9.


How many "K" call signs?


How many "W" call signs?

2877. The "W"s win by a huge margin.

We have a KAAA and a KZZZ, but no WAAA or WZZZ.

What are the oddest call signs?

Puerto Rico gets the win here. WA2XPA-680, WI2XAC-740, WI2XSO-1260, and WI3XSP-1260. These four are experimental synchronous stations. Usually AM synchronous station call signs are named the same as the host station, like KKOB-770 in Albuquerque, New Mexico, which runs one in Santa Fe, also KKOB.

Which state has the most stations?

Texas takes the prize with 298, then California with 250.

Surely New York is next, right?

No. New York is #8 ranked with 168. Florida (227), North Carolina (219), Tennessee (185), Georgia (183), and Pennsylvania (180) all have more stations than New York (168). Weirdly, New York ranks just above Alabama, which has 152.

Which state has the fewest stations?

That would be Delaware with 10, followed by Rhode Island with 15 and Vermont with 19.

Coming up next: Mediumwave Oddities - Transmitter Power


Station powers listed are for their daytime service. Nighttime powers may be lower in some cases.

Sunday, July 25, 2010

Digital Radio Update

Let's take a look at the current state of the digital radio conversion process in a few selected countries around the world.


Almost a year has passed since I reported on The IBOC MESS In North America. Since then, hybrid-digital IBOC conversions (HD Radio) on the US mediumwave AM broadcast band have come to a near dead stop. There seems to be little excitement for new stations to jump on the Ibiquity AM bandwagon, what with a scattered amount of dedicated equipment available and marginal listener interest, not withstanding the large cash outlay stations need to get signed up and converted. Available receiving equipment seems to be a few clock radios, some home sound system type tuners, and car radios (which seem to be coming on strong). Portables have largely been ignored. Sangean had plans to make an intriguing little AM/FM model, the DT-600HD, however the AM band on this unit was to be traditionally analog. They dropped the product before it got to the marketplace.

Last year at August 27, 2009, we had 289 licensed IBOC AM outlets, per FCC files. As of this writing we have 293, and two of them are silent. This is a net gain of only four new registrations in the last 11 months. In the past year there have been reports of several stations switching off their digital signal due either to problems, interference complaints, or lack of interest, so the actual count of stations currently transmitting IBOC is almost certainly under 290. Using the figure 293 against the total number of licensed AM broadcast stations in the US (4786), the AM IBOC factor is 6.1%. At this rate, AM IBOC cannot sustain itself.

Then, there is the adjacent channel interference problem, particularly bad at night, which many still complain about. And rightfully so. Nightly, digital broadband hash continues here in the northeast and other parts of the country on the mediumwave band. Earlier this year, one evening after dark I was driving through Phoenix, Arizona trying to listen to local AM station KMVP (itself an IBOC station) on 860 KHz. It transmits at 1KW. Every time adjacent channel KOA-850 (another IBOC, at 50KW) out of Denver, Colorado peaked, KMVP was not receivable due to the digital hash. It was maddening.

Earlier this year, Ibiquity announced  2010 fire sale pricing (good through December 31) for new stations wishing to join the digital "revolution", with the stipulation that they be "stations eligible for discount pricing", whatever that means. The existing $25,000 main channel licensing fee was reduced to a remarkable figure of $10,500 if payment is made up front. Monthly payment plans (at an overall higher total figure) for those stations less able to scare up this kind of money all at once were also instituted. It seems that the original higher flow of incoming cash might be slowing down. Ibiquity claims that one new digital station goes on the air on the average of every four days. I guess this must mean FM, as the AM figures don't support this claim. It will be interesting to see if the fire sale continues into next year.

So what is the current market share for HD Radio in the US? A 7 month old Bridge Report hinted at it.

12/15/2009 Bridge Ratings: New Media's Effect On Radio Lessening

"HD Radio, though it reaches only about 650,000 people, is attracting 'considerable listening time' of about 11.5 hours a week", though Bridge says "that's down from previous surveys, attributing the change to a larger number of HD receiver owners, diluting the impact of the heavy users."

"Respondents were also asked what audio devices they use every day, with a choice of AM/FM radio, HD Radio, cellphone, satellite radio, and Internet radio. Nearly 90 percent of radio listeners also use a cellphone every day, while more than 44 percent use an MP3 player. About 35 percent listen to Internet radio every day, with satellite radio and HD Radio well behind."

6/30/2010 Bridge Ratings: Is Terrestrial Radio Ready for a Digital Future?

Things are not moving along very quickly. Back to mediumwave, we can only hope that Ibiquity eventually gives up on the mediumwave band, or the government does, or both, and they take the AM patient off of life-support.

Beyond our borders, several other countries have issued mandates to go digital for some or all of their radio broadcasting services. Let's examine some of their stories.


4/14/2010 Mexico Is Set to Elect IBOC

Information out of Mexico is paltry, and I have seen nothing new since April. It would seem that this is a done deal, with Mexico on the verge of adopting IBOC as their standard. Back in May 2008, a 200 mile wide border zone was established along the US - Mexican border allowing Mexican AM and FM stations to use the IBOC format to "take decisive action so that the country’s AM and FM radio stations in the zone located within 320 km of the northern border of Mexico can transmit at the same technological level so that they can provide the benefits of quality service to the radio listening public."

Supposedly, there are two, or six, or nine IBOC outlets, depending on what you read, and at least two more deeper down in Mexico itself in or around Mexico City (XHDL and XEDA). The two call signs I have seen reported along the US border are AM outlet XEEZ 970 Radio Palacios from Caborca, Sonora, and the other, an FM outlet, XHTY-FM 94.5 in Tijuana. The station news is all old news anyway and reported a long time ago, way back in June 2008. I have heard no other IBOC-rollout fanfare since then.

Suddenly in early 2009 Mexico announced that it intended to convert all AM radio station outlets to FM, country-wide, a wholesale disbanding the AM service. They even published a schedule of the conversion dates, to take place between August of 2009 and August of 2010 (see page 8).

Whether this eventually happens or not is anyone's guess, but you can bet on it not happening by next month. Local reports out of Mexico indicate that some regional areas have abandoned the AM mode, particularly in the southeast. The government's general idea, I think, was to force the big city AM outlets to convert to FM (and in the future, IBOC), and let the rural outlets languish and eventually disappear. However there was no lack of border blasters in southwestern Arizona, where I spent last winter. The Nogales to Tijuana border strip has a sizable number of AM outlets, but none running IBOC as far as I can remember hearing. Assuming I get to Arizona again this winter, I will pay more careful attention to what is coming out of Mexico. Needless to say, the AM to FM conversion in Mexico is coming along slowly. And IBOC even slower. So where does this leave Mexican AM IBOC?

Curiously, Mexico's announcement of being on the brink of voting to adopt the IBOC methodology is some months old now, with no action since. It seems they can't pull the trigger. Maybe they realize that it's just a whole lot of money and effort for no good end, at least on the AM side. Or maybe they are dragging their feet waiting to see what happens with IBOC in this country. IBOC may be on life-support for the mediumwave band in the US, but FM has greater presence. As of this writing, 1569 stations (8 not on the air) are shown with IBOC permits in the FM service. This is compared to a total of 9608 full-fledged FM stations on the air, commercial and non-commercial, 130 of them showing silent at the moment. Using the figure 1569 against the total number of licensed FM broadcast stations (9608), the FM IBOC factor is 16.3%. Still not a great showing. However, listenership seems to be coming around.

May 2010 FM HD Radio is Becoming a Fact of Life for American Radio (be careful with this news, it is an Ibiquity article)


Canada (having wanted to go with the DAB standard) seems to be stalled on the whole digital radio broadcasting question, according to a recent article this month in Radio Magazine Online. The article reports that "government observers agree that the service has reached the end of the line....with DAB's imminent demise, increased demand for analog FM frequencies is taking place in Canada's urban areas."

IBOC, where for art thou?

"While posts in online Canadian radio forums suggest a preference for HD Radio among hobbyists, government regulators and industry representatives still treat the the option with caution. Canada's Communications Research Centre, a governmental research body with an advisory role on telecom policy, has developed its own coverage analysis tool dubbed COVLAB to evaluate digital radio coverage and spectral compatibility, rather than simply deferring to U.S. data. IBOC digital radio testing has been conducted in Canada since 2006, and the Canadian government has said that it will accept experimental HD Radio digital hybrid applications from licensed FM stations, though few stations have stepped up to do so."

"So industry opinion on IBOC's potential in Canada is checkered at best. With many stations moving away from AM altogether, and interference concerns among those who remain, AM HD Radio is probably a nonstarter."

Exactly what I've been talking about. Canadian reader Greg writes:

"DAB failed in Canada because there was almost no public awareness of it and virtually no receivers on the market that could receive it. I never saw anyone selling or even advertising DAB receivers, and never even heard any mention of the service anywhere except on radio hobbyist sites and mailing lists. Canada's DAB system was a bit different than that adopted in the U.K., operating on a different frequency band. I wonder if it would have been more successful had we adopted the British standard, which would have enabled us to use receivers designed for the U.K.?"

7/7/2010 Canada DAB Shut Down

Outside of North America, at least four more countries are either entertaining or have adopted Digital Audio Broadcasting (DAB) or Digital Radio Mondiale (DRM) schemes. Europe and many parts of Asia have gone or are going with the DAB or DRM schemes.

Also see:

Digital Radio Mondiale Home Page
Country Information for DAB, DAB+ and DMB


Britain is an interesting story, in and of itself. The government is going gangbusters for DAB "Digital Britain" via the Digital Economy Act, and pushing it as hard as they can. However, the public and the pundits are panning it for now as "not ready", if ever. The government stipulates that the 2015 switchover "will go ahead only if 50 per cent of radio listening is via 'digital platforms' by 2013." Many say that will never happen by that soon a date, and that the switchover should be delayed for a period of ten years or more. At the forefront is the BBC. The BBC's digital radio stations now cover 86 per cent of the country (signal pattern coverage). The corporation has built 50 transmitters in the last year and plans 60 more in the next year to increase coverage to 90 per cent. Of course, nationwide, the thrust is mostly FM.

Whether their switchover happens by 2015 is the guess of the decade. Figures published showed that the audience share for digital radio in Britain – including listeners on digital TV and the internet – is rising at a record rate, up to 24 per cent from 20.9 per cent in the previous quarter (first quarter, 2010).

We shall see, if we all live long enough. No IBOC for Britain.

There is lots of interesting digital conversion news out of Britain:

7/22/2010 More On The Digital Economy Act

7/8/2010 Digital Radio Speech by the Culture Minister, Ed Vaizey

7/8/2010 Relax. Digital radio switchover will now never happen

5/23/2010 Digital radio switchover gets poor reception

4/8/2010 Say goodbye to your transistor radio, digital switchover is coming

9/9/2009 Britain Mulls Over Digital Radio Transition

6/16/2009 Digital Britain: Analogue radio switch-off set for 2015


India is going with DRM, and All India Radio has just ordered a fair amount of equipment. All India Radio is also big into shortwave, much of it used for national regional service. On mediumwave, transmitters there tend to be big boys - 100KW, 200KW, and 300KW to extend the coverage area. On the books are 34 new MW transmitters, upgrades to 36 existing MW transmitters and the purchase of 5 SW transmitters and other associated equipment. Interesting, I see no mention of FM in here.

7/1/2010 All India Radio tender notice for DRM digital transmitters

4/10/2010 Indian government approves country’s digitalisation plan using DRM


Australia has gone with the DAB+ method, a variation of DAB. All commercial and public service broadcasters are now broadcasting digital radio in Sydney, Melbourne, Brisbane, Perth and Adelaide. Australian commercial digital radio services switched-on progressively in May and June 2009 in the five state capital metropolitian areas. The public service broadcasters switched on 1 July 2009. A recent report revealed, "....the industry recently released figures indicating there were already nearly 500,000 people listening to digital radio across those markets."

"There are no plans at this stage to switch off AM and FM radio services", the report said. It continued on, "As there is an estimated five radio devices per home, listeners must be given time to change over all of their radios before any discussion of the switch off of analogue services. In addition, planning needs to continue for the switch on of digital services to the rest of Australia outside of the five metropolitan capital cities."

"It is expected that it will be some years before digital radio is extended to the bulk of the Australian continent. Australia's vast distances and low population density are not well suited to the propagation characteristics of DAB+ and it is therefore likely that a standard other than DAB+ will be adopted for serving areas outside the major cities."

At the moment, it looks like IBOC has lost out here. Australia may use DRM to fill in the nether regions if DAB+ doesn't work out.

Digital Radio In Australia (Wiki)

Digital Radio FAQs For Australia

7/19/2010 ABC Radio Is Now Digital (including AM outlets)

5/5/2010 Digital radio trial to begin in Canberra

8/13/2009 Rollout Of Digital Radio In Australia (announced in 2007)


Brazil is huge. Ibiquity has done IBOC testing here, and the HD Radio system has been used on a trial basis by a number of commercial broadcasters since 2005. Brazil is the second-largest radio country in the world in terms of station count, behind the United States. Brazil has more than 3,000 commercial stations and about an equal number of low-power community radio stations. This would be huge profit for Ibiquity.

"Brazil's target date for full roll-out of an IBOC approach to digital radio is the year 2016. The Congress of the Brazilian Association of Radio and Television Broadcasters is expected to make a standards announcement by the end of this year or in early 2011. However, there is also interest in Digital Radio Mondiale's DRM30 and DRM+ technologies. The possibility exists that the country will adopt different standards for AM, FM and shortwave."

"While AM and tropical-band shortwave remain important in large swaths of Brazil, DRM may be better positioned than Ibiquity's HD Radio AM for these wavebands, according to anecdotal comments on Brazilian digital radio message boards, blogs and press accounts. Yet HD Radio has more receivers on the market than does DRM. If regulators opt for DRM on AM and for HD Radio on FM, there is a concern that the rollout could be delayed by the manufacturing time necessary to produce dual-standard receivers, according to these accounts. Ibiquity publicly has supported the use of DRM30 for shortwave services in Brazil. It also supports the concept of multi-system tuners capable of receiving both HD Radio on AM/FM and DRM on shortwave."

IBOC is at the doorstep here, but not through the door yet. Again, like Australia, the rural regions may need to adopt the DRM technique for the AM service. We will soon see what Brazil decides.

5/27/2010 Brazilian Broadcasters make public open letter in support of DRM

5/12/2010 Brazil Could Pick Digital Standard in 2010


According to the Ibiquity web site, there are a handful of other countries testing and evaluating IBOC digital radio as of this writing. They are: Argentina, Austria, Canada, Chile, France, Hong Kong, Indonesia, New Zealand, Nigeria, Phillippines, Poland, Switzerland, Thailand, and Ukraine.

Ibiquity International

Monday, July 19, 2010

The AM Broadcast Station Self-Inspection Checklist

AM Broadcast Station Self-Inspection Checklist (Sept. 2009)

As a mediumwave DXer and a person interested in radio in general, you might be interested in what the FCC requires of mediumwave AM broadcast stations in their day-to-day operation. A document exists, called the AM Broadcast Station Self-Inspection Checklist. The FCC has developed it to assist broadcast station management in conducting a self inspection of their station. It provides an opportunity for the broadcaster to review and correct any deficiencies associated with the operation of a station without an actual on-scene visit (and citation!) by the Commission. Some interesting entries are to be found, and I will cover them in this article.


First of all, the paperwork. Stations must keep logs and records. What is the difference, you might ask? What goes into a log and what goes into a record?


STATION LOGS include entries pertaining to equipment status, equipment calibration, the Emergency Alert System (EAS) and, when applicable, the recording of tower light outages.

STATION RECORDS include, but are not limited to chief operator designations, equipment performance measurements and AM Directional field strength measurements.

Station logs and records are to be retained for a period of two years.


This is a hot topic with me. Stations seem to identify less and less. There are stations (ESPN Radio, Radio Disney, are you listening?), which never seem to identify with call signs, making our task as mediumwave DXers a little more difficult. What is the rule? Well, here it is spelled out in exact terms:


Station identification shall be made at the beginning and ending of each period of operation, and hourly, as close to the hour as feasible, at a natural break in program offerings. The identification shall consist of the station's call letters immediately followed by the community of license. Any reference to additional communities must be made after the community of license. The name of the licensee, or the station frequency, channel number, or both, may be inserted between the call letters and community of license. No other insertion is permissible. Simulcasted AM and FM stations may identify jointly if owned by the same licensee.

Not much room for ad-lib here. Stations must identify at least once per hour on the hour, and in a strictly defined format. Exclaiming, "ESPN Radio!", "Radio Disney 1650!", "Power 101!", or "K-Lite 107!" cannot be used for the official identification. They must state the station's call letters and community of license at minimum. Optionally, they may insert the owner's name, or frequency, or channel, or all of these. Finally (capitalization mine): "NO OTHER INSERTED INFORMATION IS PERMISSIBLE." What's so hard about this?


A tower is a thing of beauty to the radio aficionado. Somebody even produces a tower calendar. Ah, the mediumwave broadcast tower! Think of it! Stately, striped sentinels with strobe lights flashing, they number thousands and thousands across the country, each emitting invisible waves of electrons through the late night air, spanning that mysterious thing called "the ether" to deliver communication to unknown distant masses. It conjures up thoughts of far-away points on the landscape, souls crouched in cramped corners with headsets fixed in the dark of night, straining to make sense of distant babble through static crashes and heterodynes. That would be me. The whistle of a far off freight train gives the same feeling of wonder. So, back to the broadcast tower - what is the broadcast station's responsibility?

Well, any tower over 200 feet tall or even if under 200 feet and an impediment to aircraft navigation must be registered (FCC Form 854). It also must be lighted and painted. We've all seen the lighted towers of AM broadcast stations. Ever wonder about those lights? What happens when one goes out? Who checks to see if they are burning, and how often?


The lighting on tower structures is to be observed at least once every 24 hours either visually or by observing an automatic indicating device; or alternatively the licensee/tower owner may provide and maintain an automatic alarm system to constantly monitor the lighting on a structure. All automatic or mechanical control devices, indicators, and alarm systems are required to be inspected at intervals NOT TO EXCEED 3 months.

Relief here, maybe, for the engineer. As of 1996, responsibility for tower lighting (and painting) lies with the owner of the structure, not necessarily the station licensee. However, at least a human doesn't have to go outside once a day and look to see if the lights are burning. An electronic monitoring device can perform the task. However, then the MONITORING DEVICE must be inspected at least every three months! Note: A recent directive relaxes this requirement to a year.

More on tower painting:


The station authorization and/or tower registration specifies the painting and lighting requirements for your operation....The licensee must make certain that the number and placement of paint bands and lighting match exactly with that shown on the station authorization and/or tower registration. The licensee/tower owner should also be aware of the requirement to clean or repaint tower structures as often as necessary to maintain good visibility to aircraft.

Exacting detail is found in FCC Form 715-715A:

Antenna structures shall be painted throughout their height with alternate bands of aviation surface orange and white, terminating with aviation surface orange bands at both top and bottom. The width of the bands shall be equal and approximately one-seventh the height of the structure, provided however, that the bands shall not be more than 30.48 meters (100 feet) nor less than .46 meters (1 1/2 feet) in width. All towers shall be cleaned or repainted as often as necessary to maintain good visibility.

All high and medium intensity lights shall be synchronized to flash simultanously at 40 pulses per minute. The light system shall be equipped with a light sensitive control device which shall face the north sky....

Additionally, Form 715-715A goes into great detail on the positioning and intensity of tower lights.

Section 2D, PAINTING/LIGHTING finishes by saying:

....One of the most common problems associated with tower painting is the feedlines that are on the outside legs of a tower. In many cases, the tower is painted correctly, but the solid black colored feedlines defeat the purpose of the painting by covering the outside legs of the tower. The licensee/tower owner should make certain that the feedlines are also painted in such instances. This does not apply in cases where the tower is authorized for strobe lighting.

To wit: If you run your feedlines up the outside of the tower leg, paint the feedlines to match the tower striping! So that's what they call that red color on towers: aviation surface orange.

And let's not forget to notify the Federal Aviation Administration when the lights go out:


The tower owner/licensee is to notify the Federal Aviation Administration (FAA) at (Phone: 877-487-6867) within 30 minutes of the observation of an improper functioning or extinguished top steady burning light or ANY flashing obstruction light regardless of its position on the structure. Such improper functioning beacons include non-lighted beacons as well as those that are lighted, but non-flashing. Notification is to also be made immediately to the FAA once the beacon or steady burning top light is returned to service. Notification is not required when side light outages are observed....

Bottom line: you have 30 minutes to notify the FAA if your top tower light or one of your flashing lights goes out!


Lots of rules exist about checking and maintaining station transmitter power and purity of signal. Stations are granted the privilege to transmit at a certain output power. How much leeway do they get to be over or under powered?

Section 4A. POWER:

All AM stations are to maintain antenna input power between 90% and 105% of that authorized.

Interesting, we are allowed no more than 5% over and 10% under. Accordingly, a 50KW station can actually run between 45KW and 52.5KW and still be in compliance. I wonder how many 50KW stations push the envelope and run that extra 2.5KW? Or more?

Section 4A continues on, concerning failure to maintain a minimum power level (90%):

....The power is to be maintained as near as practicable to the station's authorized power. In the event that it becomes technically impossible to operate at authorized power, a station may operate at reduced power for a period of not more than 30 days without specific authority from the FCC. If operation at reduced power will exceed 10 consecutive days, a notification must be sent to the FCC, Media Bureau, Washington, D.C. 20554, no later than the 10th day. If normal power is restored prior to the expiration of the 30 day period, the licensee must notify the FCC upon restoration of normal operation.

It's kind of like highway speed limits. The cops will ticket you for going more than 10 mph over and let you by at 5 mph over. You will also get ticketed for going to slow on certain roadways, i.e. 35 mph in a 55 mph zone.

So how exactly does a station measure its power level accurately to assure compliance with the FCC?


Okay, we need to check the power. Do we just read it off a meter on the console and log it? Well, perhaps.

Section 4B. DIRECT vs INDIRECT METHOD (of monitoring power output):

The antenna input power of AM stations must be determined using the direct method. However, the indirect method may be used on a temporary basis when it is not possible or appropriate to use the direct method due to technical reasons.

Direct Method. Two possibilities are allowed here:

1) Employ a suitable instrument for determining the antenna's input power directly from the RF voltage, RF current, and phase.

2) Calculate the product of the licensed antenna or common point resistance at the operating frequency and the square of the indicated unmodulated antenna current at that frequency, as measured at the point where the resistance has been determined.

Indirect Method.

Apply the appropriate factor (they mean efficiency factor here) to the input power to the last radio frequency power amplifier stage of the transmitter, using the following formula:

Transmitter output power = Ep x Ip x F


Ep = DC input voltage of final radio stage.
Ip = Total DC input current of final radio stage.
F = Efficiency factor of the transmitter.

The value of the efficiency factor, F, is to be determined and a record of its value is to be maintained and available upon request. Licensees must make certain that all duty operators know which method of power determination is being used and how to calculate the output power based on that method.

Furthermore, how does a station ensure that its signal is clean and meets prescribed standards?


Not only must a station monitor power and other parameters, but it must have procedures in place on how and when to do it.


The licensee must establish monitoring procedures and schedules for the station. Monitoring procedures and schedules must enable the licensee to determine compliance with operating power, modulation levels, AM modes of operation, and where applicable with antenna tower lighting and AM directional antenna parameters. Licensees should be able to provide upon request made by the FCC, the monitoring procedures and schedules they have established for each station. In the event that an AM broadcast station is operating with a mode of operation not specified by the station license, then the station operation must be terminated within 3 minutes or the station output power must be reduced sufficiently to eliminate any excess radiation. This includes AM Directional stations with parameters or monitoring points out of tolerance with the station authorization.

Additionally, the directive states:

....In the event that an AM broadcast station is operating with power in excess of 105% of authorized, or with excessive modulation, then station operation is to be terminated within 3 hours, unless corrective action is taken prior to that time.

All right, it basically boils down to this: A station must have a monitoring procedure in place (obviously written), and a schedule in place for when to do it. They must monitor, at minimum, the power output, modulation level, AM quality, antenna lighting, and antenna directionality. And if their monitoring shows that they are out of compliance, they must shut down within three minutes, or at least reduce power to bring them back into compliance! The only exception is if power is exceeded or modulation is excessive - in which case they have three hours to terminate operation.


A station is licensed to transmit on a specified frequency. Along with measuring power output, a station must also ensure that it is on frequency. How accurate is it required to be?

Section 4C. FREQUENCY:

The carrier frequency for monophonic transmissions or the center frequency for stereophonic transmissions may not depart more than 20 Hz from the assigned frequency.

Tune across the broadcast band some night when conditions are good and listen for heterodynes. On any given channel there should be none, ideally. You have to listen carefully. Listen for that faint, low "whump, whump, whump" beat note caused by one station being ever so slightly off frequency, usually only a matter of cycles. 20 Hz offset is too low to hear as a tone. It is more of a rapid, dull thump-thump-thump, 20 times per second. If you hear a tone, a station is way off frequency, much more than 20 Hz (cycles). Surprisingly, you will find some.


Over-modulation is sometimes a no-no, too much over-modulation is a definite no-no. It results in distortion of recovered audio when the signal is demodulated, and worse, interference to stations on nearby frequencies due to the spurious byproducts. Here's what the FCC has to say about it:

In no case shall the amplitude modulation of the carrier wave exceed 100% on negative peaks of frequent recurrence, or 125% on positive peaks at any time.

Slight over-modulation on the positive portion of the waveform is sometimes used for a more punchy sound, and works within limitation.

Any time you exceed 100% modulation on the negative portion of the waveform, it is clipped because you can't have less than zero carrier signal; that clipping generates high order harmonics that cause sidebands far outside of your intended channel and will interfere with other stations above or below the operating frequency.


Back to station output power again. If a station's service is not "Unlimited", it will generally be required to operate at different power levels for daytime, nighttime, and possibly even during the "Critical Hours" period. Critical Hours are the first two hours of daylight after sunrise and the last two hours of daylight before sunset.

Of course throughout the year, sunrise and sunset times are changing every day, therefore, stations must be constantly updating the times when they change power levels. The FCC is very specific on this. Let's see what this section of the document has to say:


Most AM stations utilize more than one power mode of operation. In addition to the normal authorized daytime power many stations operate under the reduced power pre-sunrise service authorization (PSRA) and post-sunset service authorization (PSSA)....Some stations will have reduced power nighttime operating authority and a few stations have a specified critical hours reduced power authorization. The times when power changes are to occur are clearly shown on the station authorization and in readily available sunrise/sunset tables.

(See for a table of the sunrise/sunset times for your area).

Any unauthorized departure from an operating schedule will be considered as a violation of a material term of the license. It is the responsibility of the licensee to maintain calibrated time keeping devices, power switching devices and other equipment necessary for the timely change in power to occur as authorized. In addition, should the station be operated with more power than authorized for that time of day, then all operation is to be terminated within 3 minutes. The logging of power mode changes is not required unless the station is operating out-of-tolerance with any operating parameter. However, licensees are encouraged to do so.

As already stated, the FCC is very specific on power changing. Stations must keep accurate timing and change their power accordingly and on time. They must determine (on their own), their local sunrise/sunset time and change power precisely at that time. If they are out of tolerance by as little as three minutes, THEY MUST SHUT DOWN OPERATION. This is a stringent requirement. Violation of this requirement is a violation of the terms of their license. I would venture a guess that there are more than a few stations that are not changing power exactly on time. I know of some locals that are most definitely not within the three minute window.

So there you have it - the FCC's basic checklist on how to run an AM broadcast radio station. Hope you enjoyed it.


Other FCC self-inspection checklists