One of the AM stations around here that I am familiar with is considering a downgrade, which is to say reduce power and get rid of a directional antenna system in favor of a non-DA antenna. In this particular case, it makes sense, as the station can co-locate with another AM that is closer to the COL by a good distance. The coverage from the new site at reduced power looks to be a good fit. If this can be arraigned, the AM station in question would lose a multi-tower AM antenna system that is 50 years old and all the attendant headaches, expenses, and labor that goes with it.
Many AM stations that are DA-2 or even DA should consider downgrading to a lower power level and getting rid of their DA system. Directional antenna systems on AM stations are maintenance nightmares. Unfortunately, in the ’50s, 60s, and 70s, it was often thought that adding power, and extra towers to an AM station would give them great swaths of extra coverage. Sometimes it worked out, sometimes it did not. Often what happened was some area was added, but in areas that were nulls toward protected stations, signal strengths went down. What the station ended up with was more towers, more maintenance, monitor points, a sample system, and more expense.
Taking an AM station in the other direction might actually make more sense. Go back to one tower non-directional 1 KW or whatever power can be used in the daytime. Time was when the FCC would only allow certain power levels; .5, 1, 5, 10, and 50 KW. Those were what a new station had to work with. No longer is that the case, any power level can be used so long as it meets interference contours and the city of license contour coverage requirements.
Presunrise authority is normally 500 watts and is available at 6 am, post-sunset authority varies but often a PSA extends the on-air time to 9 pm in the wintertime. For a local radio station, which is what all but the class A AM stations are destined to become, this will be adequate. For a losing station, it may be that, or turn in the license and sell the land to a developer.
Diplexing on another AM station’s tower closer to town is also a good way to get out of maintaining an expensive antenna array with diminishing income.
I was digging through some old manuals at the shop today and I found this June 1987 memo from Orban to AM stations titled “AM radio CAN sound almost like FM.”
The main purpose of the memo was to get AM radio stations to implement the NRSC standard for pre-emphasis and high-frequency roll-off to improve the sound of AM broadcasts on ordinary radios.
I am not sure why the receiver manufacturers never designed an IF filter that would be compatible with NRSC, it seems like a fairly simple design. Instead, what we have is “digital” AM radio (IBOC) which does not work well, and creates many more problems with interference than pre-NRSC broadcasting.
If one were to look at the entirety of AM broadcasting history, one would find some striking parallels with what is happening with IBOC today on both AM and FM.
To start, the NAB began petitioning the FCC to allow more AM broadcasting stations, even as it was known that these stations would create interference with existing stations, especially at night. Still, the NAB persisted and the FCC relented and through the fifties, sixties, seventies, and eighties many more class II and III stations were established on what used to be clear channels (classes I and IA).
Once the AM band was chock full of stuff, they began going to work on the FM band with 80-90 drop-ins.
You see, for the NAB, more radio stations means more dues money, and greater lobbying power because of the larger size of the industry. Then came the deregulation of ownership limits. By this time, Big Group Radio was calling the shots and they wanted more. This led to the great consolidation rush of the late 1990s from which the radio industry is still reeling. The consolidation rush led to highly overpriced radio stations being leveraged to the absolute maximum, leading to recent bankruptcies.
Finally, the NAB’s great push toward adopting IBOC digital radio in the early years of the 00s. IBOC was supposed to save the day, greatly improving the quality of both AM and FM and bringing radio into the 21st century. Except that the promised technical advances never materialized. IBOC remains a great expensive boondoggle and I am beginning to think that perhaps we should stop listening to the NAB.
The memo itself is a fascinating thing, which was one could substitute AM with RADIO and come to some of the very same conclusions today regarding analog and IBOC digital radio. For example, this paragraph on AM stereo:
AM stereo was thought to be an answer (to improve AM), but AM stereo was embraced with the false assumption that having ‘stereo’ automatically meant having ‘high fidelity’. While AM stereo did provide somewhat better fidelity, it was not comprehensively engineered to get the best fidelity from AM. It was hoped that the gimmick of having two channels would be enough to save AM.
AM stereo could have been an improvement, had it been properly implemented. Unfortunately, the underlying problem of bad-sounding receivers was never addressed. About which, the same memo notes:
Receiver manufactures did what they could to reduce listener complaints – – they narrowed the bandwidth (thereby reducing audio fidelity) until the complaints about interference stopped. Listeners clearly indicated, through their buying habits, a clear preference for lower fidelity over continuous irritating static, buzzes, whistles, and “monkey chatter’ from adjacent stations. People accepted this situation for a long time – – until the simultaneous advent of improved receiver technology and the FCC’s anti-simulcasting rules created the FM boom of the late 1970’s. (ed note: I remember listening to FM because there were fewer commercials, not better sounding audio)
Then the memo goes on to stress the importance of implementing NRSC standard for AM broadcasting that included the sharp frequency roll-off at 10 kHz, noting that receiver manufacturers would design “fine new receivers” that would take full advantage of the new standard, but only if broadcasters first showed good faith by widely and promptly implementing it.
As I recall, NRSC-1 was adopted as a rule of law by the FCC in 1989, about two years after this memo was written. One could reasonably expect that receiver manufacturers then started producing radios that took advantage of the NRSC pre-emphasis curve with IF filters that did not cut off audio frequencies above 3.5 kHz, but rather rolled them off in a gentle slope until about 7 kHz, more aggressively after that until 10 kHz, where they cut off.
Except they didn’t.
Instead, twenty years later, AM radios universally sound bad, with an audio bandwidth of about 3 kHz or so.
I believe that AM receivers could be made with three IF bandwidths, automatically selected based on signal strength. Within the 5 mv contour, full (10 kHz) audio can be reproduced using a high-frequency roll-off described above. In the 1 – 5 mv contour, a 6 kHz bandwidth and less than 1 mv a 3 kHz bandwidth. The automatic selection could be defeated with a “wide/narrow” IF bandwidth selection switch like the GE super radios have. Of course, if one were listening to stations transmitting AM IBOC, the “narrow” setting would be the best.
Half of me thinks that the ship has already sailed on AM broadcasting. The stations on the air will continue to decline until they are no longer able to broadcast due to expensive repairs or replacement, at which time they will be turned off. The other half thinks that AM radio, as evidenced by the huge public response to WEOK and WALL broadcasting the true oldies channel, can be revived. With the impending inevitable FM IBOC power increases, translator shoe-ins, LPFM, etc; the FM band may become worse than the AM band. At this point, the public will have to decide whether free radio is important to them, or 3G/4G services will become the new method of broadcasting.
I am a strong proponent of non-computer-based air chain processors. Something about listening to dead air while the computer reboots is annoying and every computer needs to be rebooted every now and again.
All of that being said, I recently had a chance to play around with Breakaway Broadcast audio processing software. I have to say, as a low-cost, very versatile platform, it can not be beaten. I would put it up against any of the high-end FM audio processing, provided one uses a high-quality sound card with an adequate sample rate.
Claesson Edwards Audio has developed several software-based audio processors for a variety of end uses. They make several recommendations for hardware and operating systems, Pentium 4 3.2 GHz or better, dual-core preferred. If one is interested in using the sound card to generate composite audio, then any sound card capable of a true 192 KHz sample rate will work. They list several that have been successfully tested on their website.
For approximately $1,200 dollars or so, one could buy a decent computer, the Breakaway Broadcast software, and the Airomate RDS generator software. For a Mom and Pop, LP, or community radio station that is looking to do some high-end audio processing and or RDS, that is a good deal. I would add a UPS to the computer and keep backup copies of the software installed on an emergency computer just in case. One can never be too safe when it comes to computers, viruses, hackers, and other malicious persons.
Things that I like
Inexpensive, the fully licensed version is $200.00. The demo version is free but there is a 30-second promo every thirty minutes.
There are several factory presets, but everything is fully configurable, changes can be named and saved allowing some experimentation.
Audio cards with 192 KHz sample rate or greater can be used to generate composite audio, eliminating the need for a separate stereo generator
RDS capable with additional software (Airomate2, approximate cost $35.00)
The same processing computer can be used for streaming audio and or AM audio processing simultaneously.
A full set of audio calibration tools for AM and FM transmitters allows correction for tilt, overshoot, and linearity. Can add pre-emphasis at any user-selectable rate.
Fully adjustable phase rotators.
Things that I don’t generally like:
A computer-based system using Windoze operating system
WXPK in White Plains, NY has been using this software to process their streaming audio for about 2 years now. The software itself is extremely stable running on a stand-alone Windows box with XP service pack 2.
I believe it is time that we consider the fate of Channels 5 and 6 as they relate to current radio service. These channels have proven difficult for television broadcasting, and I have a hard time imagining that they would fare much better as additional spectrum for mobile broadband use. This spectrum is not well suited for digital transmissions. It certainly is possible that this spectrum could be used for LPFM, expanded NCE use, and AM broadcasters.
That would, indeed, be an interesting development, if it were allowed to happen. Of course, there are quite a few hurdles to get over, even if it gets the FCC’s nod, which is a long shot, to say the least. There would likely be some type of congressional “input” into the matter, which could stall things for years if not forever, depending on which way the money flows and which one of our wonderful congressional representatives can be bought and sold.
Getting new radios on the market with the expanded FM band (77 through 87 MHz) will take some time. Thankfully, unlike HD radio, no licensing fees will be required. Manufacturers simply need to increase the frequency range down. It might take several years, but it would happen eventually, as is the case with expanded AM band radios, which are universal now.
Existing AM stations should be given the option to move, those that stay on the AM band will get the option to improve their facilities or go non-directional as the interference contours allow.
Those that choose to abandon AM need to surrender their AM license before commencing broadcasting on FM, none of this expanded band crap where they were supposed to surrender licenses after five years and never did.
Those that choose to abandon the AM band also will not be assured the same theoretical coverage areas they had on the AM band.
AM migrants should not have to compete in an auction.
Indeed, if LPFMs get a boost in the process, all the better. It might actually give radio the shot in the arm it needs, add a good deal of local competition, and satisfy several needs.
