The AM HD all digital test, part III

Continued from part II:

Can the AM broadcast service be revitalized and returned to relevancy?  If so, how?  The previous post demonstrated that AM radio services problems are multigenerational and multifaceted.  There is no one solution that will make everything better.  Pushing an all digital solution will not solve electrical noise issues or the overcrowding issues on the AM band.  It will not address the paucity of local, unique programming that is the bread and butter of successful AM operators.  Because the issues that face AM operators cover many different areas of broadcasting, any proposed solution must address every aspect.  Any proposal that simply addresses the poor fidelity, for example, will simply be another band-aid (no pun intended), placed on top of numerous others which have been previously ineffective.

The FCC is looking for deregulatory solutions to the AM problem.  Deregulation and the FCC’s lasissez-faire attitude is exactly why the AM broadcast band is in the condition it is today.  Relaxed technical standards have allowed the creeping crud to take over like Kudzu.  Further deregulation will only exacerbate the problems.

In broad categories, AM radio’s problems are:

  • Noise and interference
  • Low fidelity
  • Lack of ratings
  • Low profitability

Electrical Noise on AM broadcast band

In order for any solution to be effective, this problem must be addressed first.  Noise and interference are at the heart of the technical issues confronting the typical AM radio listener.  These problems come from multiple sources, but the worst of which are electrical devices such as CFL’s and other fluorescent lights, LED lamps, street lights, utility company wires, computers, computer monitors, TVs, power line communication, appliances and other intentional emitters.  The FCC has, within it current powers, the ability to address at least some of these noise generators.  Devices like CFL’s, LED lamps, computers and others are regulated under Part 15 and 18 of the FCC rules.  While there is little that can be done with fluorescent lights (they work using an internal electrical arc), other emission standards can be tightened and better, more specific warning labels can be implemented on packaging.

Station to station interference on the AM broadcast band

Another aspect of this problem is mutual interference on the AM broadcast band.  In short, too many stations are licensed to a small slice of the electromagnetic spectrum.  The increasingly poor condition of many directional antenna systems ensures that there is a cacophony of interference at night.  While this is a politically sticky situation, some tough love is needed to solve these problems.  There are many under performing AM stations on the air that are junkyards of last ditch formats that have little or no hope of success.  These stations are often technical disasters that pollute the spectrum with interfering signals.  Compounding this issue is the transmission of IBOC at night.  The current iteration of IBOC (HD radio) intentionally transmits on adjacent channels creating more problems than it solves.

Confronting any of these issues is almost certain to be a non-starter and that is a shame because real, meaningful steps can be taken here.

One scenario would be a one time test, applied during the next license renewal cycle, that allows station owners to assess their operations.  Those that do not pass the test would be able surrender their license for a tax credit.  This type of culling is not unprecedented, as the FRC did something very similar during the early days of broadcasting when the AM band became a free for all.  The test should have three areas of consideration; technical operations, programming and business profitability.  Something like this would be a reasonable example of a re-licensing test:

Technical operations
Test Points
Does station have its own studio 1
Are DA parameters or base current as specified on license 2
Is antenna array being maintained, field mowed, trees cut, tower fences secure, signage posted, catwalks or access roadways maintained 1
Does station have a working backup transmitter 1
Does station have a working backup STL 1
Does station have a working emergency generator 1
Does station have a current transmitter maintenance log 1
Are NRSC measurements up to date 1
Are monitor points measured at least biannually 1
Minimum score to pass technical operations: 5 points
Test Points
Does station originate local programing 1 point per average weekly hour
Does station have local news 1 point per average weekly quarter hour
Does station appear in market ratings survey 1 point per survey period (or 4 points for continuous survey markets)
Minimum score to pass programming test: 5 points
Is the station profitable ¼ point for every profitable quarter during last license period
Minimum score to pass business test: 3.5 points
Minimum overall score for all three tests combined: 16 points

This is a fairly low bar to get over. I generally do not advocated more government regulations and regulatory burden. However, this is one case where relaxed regulations lead to the problems currently being encountered. Perhaps a one time re-regulation would be warranted in the public interest.

Audio quality and other technical improvements

There are several areas where new technology can be used to improve AM stations technical quality.  There is a common misconception that AM broadcasting has low fidelity due to inferior bandwidth.  Truth be told, AM broadcasting can pass 15-20 KHz audio.  It is restricted to less than 10 KHz because of the aforementioned band congestion problems.  Since the NAB and the FCC has made exceptions to the NRSC-1 requirement in order to transmit HD radio, perhaps other wide bandwidth uses can be considered.  One possibility would be to allow transmission of 15 KHz audio during daytime hours, switching back to NRSC-1 standard after dark.  This may not work on local (class C) channels but for regional and what remains of cleared channels, it may offer some improvement.  Also, turning off IBOC hybrid analog/digital transmissions after dark should be examined regardless of whether an all digital solution is sought.  Hybrid IBOC is a part of the night time noise problem and not a viable solution, particularly troublesome are class A skywave signals.

Also, much benefit could be derived from requiring that all AM stations sync their carriers to GPS.  If all of the stations on the same channel are on exactly the same frequency, it will eliminate carrier squeals, growls and whines.  This is something that can be done very easily and inexpensively, especially with newer transmitters.

Double sideband AM is wasteful, as both lower and upper sidebands contain the same information.  Suppressing the lower sideband and transmitting just the carrier and upper sideband would free up quite a bid of bandwidth and reduce adjacent channel interference.  Most simple diode detectors demodulate the upper sideband anyway.

A concerted effort must be made to restore all of the technically deficient antenna systems.  Not only fixing out of tolerance DAs but also addressing bandwidth issues, general maintenance, ground systems, clearing away brush and undergrowth can all have noticeable positive effects on signal performance.

At the same time, better receivers are making their way into the market place.  Receivers that have auto variable IF bandwidth based on signal strength could greatly improve audio quality.  The auto bandwidth function could be overridden by user selected bandwidth, if desired.  I know that wider IF bandwidths are in the current chipset because of IBOC and DRM, I do not know to what extent they can be adjusted, but it is something that receiver manufactures should consider.

None of these solutions are Earth shattering, nor would they require great sums of money to implement.

AM to FM Translators

The current thought process is that using FM translators for AM stations is a fantastically great development.  For a class D AM station with little or no night time power, an FM translator is a good way to maintain service to the community.  For class C or some class B AM stations where night time interference greatly degrades the station’s service area, an FM translator is a good way to maintain service to the community.  Does a 50 KW blow torch really need a 250 watt (or less) FM translator to aide with reception in its city of license?  No.  Yet, this is how the AM to FM translator service will be rolled out, those that already have sound technical operations will be given FM authorizations.  This does nothing to actually fix AM broadcasting technical issues, it is a well meaning measure that will be incorrectly applied by the broadcasters that need it least.


All of the technology and gadgets will not solve the problem of poor programming.  This is an area where the FCC should not tread, however, broadcasting associations can assist their members with local programming issues.  Broadcasters need to understand that good local programming that is unique will attract listeners, worthless junk will not.

Continued in part IV

The AM HD all digital test, part II

Continued from part I:

In order to get to the root problems of AM (aka Medium Wave, or Medium Frequency) broadcasting, a bit of history is required.  For the sake of brevity, here is the cliff notes version:

  • Early broadcasting services were entirely AM and heavily regulated by the FRC and later FCC
  • FM broadcasting was introduced in the late 1930’s experimentally, then commercially circa 1947
  • In 1946 the FCC relaxed its regulations allowing many more AM stations to be licensed as both class II (currently class B regional) and class II-D, II-S, and III-S (currently class D) stations.  Between 1946 and 1953 the number of AM stations more than doubled from 961 to 2,333
  • In spite of FM’s technical superiority, AM remained dominant until approximately the mid to late 1970’s when the FCC forced FM stations to end simulcasting with co-owned AM stations
  • Broadcast deregulation came in small waves at first; programming rules, business rules, some technical rules, operator license requirements were done away with, enforcement of other rules became more selective
  • Deteriorating antenna systems, splatter, modulation wars, declining technical resources and increased electrical noise created interference issues
  • The electrical noise floor gradually increases as more electrical appliances, street lights, fluorescent lights, and other intentional emitters increase
  • Radio manufactures responded to consumer complaints by greatly reducing the audio bandwidth of their AM receivers
  • Broadcast deregulation greatly increased in the 1980’s
  • The FCC voted in 1980 to limit skywave protection of clear channel (class I or A) stations to within 750 miles of transmitter site allowing former daytime only stations to stay on at night which increased interference
  • AM Stereo is implemented in 1982 to improve quality and compete with FM broadcasting.  Competing systems are proposed, FCC does not mandate a standard, lets the market decide, the technology dies off
  • The National Radio Systems Committee (NRSC) is formed and comes up with a standard (NRSC-1) that restricts AM broadcast audio to 10 KHz or less, mandates yearly measurements
  • Ownership rules are loosened somewhat in 1994, then greatly in 1996
  • The expanded AM band (1,610 to 1,700 KHz) is opened up in 1997 to existing AM broadcasters.  Once stations are licensed to operate in the expanded band, they are supposed to surrender their former licenses, few do
  • The great radio consolidation takes place; 1997-2004.  Synergy is the word of the day, stations are overvalued in multiple transactions which created a debt bubble
  • Skywave listening is mostly depreciated as an acceptable communications method by the industry
  • The introduction of IBOC hybrid analog/digital broadcasting in 2002 greatly increased the adjacent channel interference issues.  Sidebands out to ±10-15 KHz of carrier are introduced with power levels of -16dBc.  For a 50 KW station, this equals approximately 2,500 watts power transmitted on each of the adjacent channels.  Analog audio of stations transmitting AM IBOC is restricted to 5 KHz, background digital noise is often present in analog audio, further degrading the quality
  • Inside electrical noise greatly increases as compact fluorescent lamps (CFL) and LED lamps become popular energy saving measures
  • Night time operation of HD radio permitted in 2007 creating greater interference problems to distant adjacent channel stations
  • There are 4,738 AM stations licensed, 89 are silent, approximately 210 transmit HD radio, approximately 66 (mostly class A and B stations), transmit HD radio at night

There is not any one development that can be singled out as the smoking gun that killed the AM broadcast band, it is rather, a death from a thousand cuts.  Because of heavy debt loads, technical, programming, promotional and personnel resources are directed away from AM stations (and FM stations too).  After staffs were reduced and news departments eliminated, AM stations became a dumping ground for mediocre satellite syndicated talk programming.  Eventually many also became a technical nightmare due to deferred maintenance.

There can be little doubt, AM broadcasting is a tough business to be in.  In spite of all of that, however, there are several AM stations that are not merely surviving but thriving.  What does it take to be a successful AM broadcaster in 2013?  There seems to be several common threads, but the two most common are a good technical operations and local programming.

Continued in Part III

The AM HD all digital test, Part I

After reading this article in Radio World it seems the all digital AM testing completed last December was “nearly flawless.” This comes as no surprise considering that WBCN is owned by CBS, also an iBiquity investor.  Could there really be another result?  I think not.  But let us examine the technical aspects of the WBCN test itself.

WBCN is on 1,660 KHz in the expanded part of the AM band.  According to the FCC database, it transmits from a single 90.7 degree tower.  As such, the tower is likely either broad banded already or easily modified to be.  Also according to the FCC database, there are eight other stations licensed to 1,660 KHz, all of which transmit with a power of 1 KW at night.  This eliminates much of the interference issues found on the rest of the AM band.  It can be further noted, the problem with electrical noise is most prevalent below 1,000 KHz.  There is little wonder in the nearly flawless results.

From a technical standpoint, this is about as favorable a testing configuration as can be conceived for AM IBOC.  If AM HD radio did not work under these test conditions, then it would never work at all.  The actual data from the tests has yet to see the light of day and it may never be released.  This is likely due to the same reason the NAB will not release its technical improvement study on AM; we simply won’t understand it.

Near the end of the article someone (it is not exactly clear who) asks the NAB, “why the opacity?” For which the answer given is “to get stuff done.”  There is a fair bit of hubris in that statement.  Is the NAB now the technology decider for the rest of us?  I think not.  Shutting out everyone but a very select few rightly causes suspicion, something that the Radio World article acknowledges.

Accurate, real world testing involves more than using one technically favorable test subject.  In fact, the tests should be run in the most technically challenged environment to present meaningful data points in real world conditions.  Stations like a six tower directional on 580 KHz, or a 190 degree tower with a folded unipole on 810 KHz, or pretty much any class C AM station at night time.  These types of test will represent at least a few of the existing antenna systems and stations.  Will that happen?  It depends on whether the FCC will hold somebody’s feet to the fire and demand meaningful testing.

Much ink has already been spilled by various trade publications debating the future of AM broadcasting.  Most take the position that there are several technical issues which makes AM broadcasting problematic if not downright untenable.  There are indeed some technical issues with AM when compared with FM or IP based audio distribution.  There are also several ways that AM broadcasting is superior to both FM and IP based audio distribution.  The truth is that AM broadcasting’s issues are complex and involve technical, regulatory and operational considerations.

These can be broken down as follows:

  • AM is prone to electrical noise interference
  • AM is prone to co-channel and adjacent channel interference
  • AM has inferior bandwidth and thus audio quality
  • AM has poor signal quality
  • AM has low or no market share

All of these problems conspire to make AM broadcasting unprofitable, or so the narrative goes.  Does all digital AM HD radio really solve any of these problems?  From the WBCN test alone, results are inconclusive.

Transmitting a signal in digital format does not make it immune to noise or interference.  It simply masks the interference until the noise floor becomes too high causing excessive bit errors, at which time the receiver mutes.  Thus, with AM HD radio in a noisy environment, the listener will not hear static, that much is true, they may not hear anything at all.  Is this all or nothing reception an improvement?

AM broadcasting audio bandwidth problems are mostly self inflicted.  AM stations created loudness wars in the 60’s and 70’s, causing splatter and adjacent channel interference on older, cheap diode detector type receivers.  Receiver manufactures responded by limiting IF bandwidths to 3-4 KHz, slightly better than telephone quality.  The industry came up with the NRSC-1 standard which limited AM bandwidth to 10 KHz or less.  For a long while, AM radio receivers remained very poor.  This appears to be changing with newer receivers that are both more selective and more sensitive.  My Toyota has a Pioneer radio which has good bandwidth on AM.  Is it as good as FM?  No, but it is certainly listenable, especially if no other station is playing that style music.

That brings me to programming, which is the real crux of the issue.  Continued in part II.