Engineering Radio – Page 182 – One Hundred percent Human Generated Content for your Reading Enjoyment

The lesser of two evils

If I had to pick between allowing HD Radio^TM a 6 dB increase or removing the third adjacent protection for LPFM stations, I’d choose LPFM.

In tests performed by NPR, Ibiquity’s In Band On Channel (IBOC) digital radio scheme created significant interference to the first adjacent channel when running with 6% of the analog carrier power (-14 dB referenced to carrier) vs. the 1% (-20 dB referenced to carrier) currently allowed. The NAB would like to see -10 dB referenced to the carrier or 10% of the analog carrier power.

Remember Bill Clinton’s sign during his first election, something about the economy, stupid. In this case, it’s the Bandwidth, Stupid. In the US and Canada, FM stations are allowed 200 kHz of spectrum to transmit their analog signals. Analog signals include main channel mono (left plus right), and sub channels for stereo pilot (19 kHz) stereo matrix (left minus right), RDS (57 kHz), and any subcarriers in the 67-92 kHz range.

HD Radio^TM radio requires 400 kHz of spectrum to transmit its digital carriers. Here come those laws of nature again, you can’t fit 400 kHz bandwidth into 200 kHz of spectrum.

Ibiquity decided to try it anyway, contravening the FCC’s rules about FM broadcasting bandwidth channels which had been in place since the advent of FM broadcasting in the early 1940s. What they attempted to do was make the power level on the adjacent channel so low that most analog radios would not have a problem with it while there was a strong signal from another station present. (hey buddy, how about a little of this new thing called crack?) This is known as the capture effect.

Now, Ibiquity created this whole thing to make some money. Nothing wrong with that, this is a market economy after all. They marketed the hell out of HD Radio^TM radio, I saw them at various trade shows, they had full-page advertisements in all the trade magazines, they hit the phones, it was a full-court press (it’ll make you really cool, you’ll be able to do things you can do now and you’ll feel really good). They would even reduce or waive the license fee (here, just take a little rock, try it, on me, you’ll see).

So they were able to sell a very expensive system that has significant coverage issues because of the low power levels needed to satisfy the FCC’s concerns about adjacent channel interference. The NAB and many of the big radio groups bought in to it (gotcha, crackhead, you’re mine now).

Now, of course, those that bought into HD Radio^TM radio want their investment to work, (which it doesn’t right now) so all the talk of power increases and hey, lets just disregard that pesky interference issue. If you ignore it, eventually it will go away (along with the entire FM band).

The problems with HD Radio^TM radio are:

Inadequate building penetration at the current power level (1% of carrier power)
Bandwidth that exceeds current channel assignments on both AM and FM frequencies.
The proprietary nature of HD RadioTM’s CODECs and licensing for second channels give Ibiquity too large a role in saying how radio is broadcast in the US. Remember, radio station licenses are granted in the public interest, the owners are trustees of the public
Complete lack of public awareness.
It doesn’t really improve anything anyway.

By the way, shame on NPR (again) for their corporate stance contrary to maintaining good quality radio and serving the public interest.

Compared to that, LPFM is a very minor thing. As I said before, removing the third adjacent protection will raise the noise floor in the FM band and by default cause more interference. However, I’ll take a little more interference created by community radio stations over the complete rack and ruin of the FM band.

FCC inspections for broadcast stations

So here you are, minding your own business on a not-so-frantic Wednesday afternoon when a guy shows up in the lobby and wants to see you. The receptionist says he has a badge and he is from the FCC.

Oh no! Panic! Mayhem! Chaos! Etc!

Actually, things are not as bad as they might seem, after all, this is not your father’s FCC.

Many stations use the state broadcaster associations’ Alternative Inspection Programs (AIP). This is where you pay a contractor from the broadcaster’s association to come out and do a mock inspection of your radio stations. After the station “passes” the “inspection” it is issued a “certificate” that “insures” it won’t be inspected by the FCC for three years.

Totally bogus, or as the French might say complete bull shit.

The stations I currently work for had those “certificates.” When the FCC inspector showed up, he laughed at them and inspected us anyway. We complained to the state broadcasters association and the head of the FCC enforcement bureau at the local field office, all to no avail. This happened four times. Each time the FCC inspectors found nothing and went on their way.

What did I learn from this? Why bother with the stupid AIPs when all that needs to be done is comply with the FCC’s rules. After all, the so-called “inspector” from the broadcaster’s association is merely going to use the same FCC checklist that is downloadable from the FCC website. Anyone can do that themselves.

I also learned that the FCC inspectors check a few things more closely than others. For example:

The public inspection file should be perfect. Since they inspect these stations all the time, they know what is usually missing; Issues and quarterly reports, Contour maps, and license renewal cards.
EAS logs and procedures. Make sure that every operator knows how to send an EAS test. Make sure that all the EAS logs have been checked and signed by the chief operator. Make sure that any discrepancies are noted.
Directional AM station operating parameters. Still a hot-button issue and one area that trips up a lot of people. All antenna parameters are within 3 percent of licensed values. All monitor points below the maximum allowed.
Equipment performance measurements. These are needed on all AM stations every year. They are carrier frequency harmonic measurements and NRSC-2 mask compliance measurements.
Tower fences and tower registration numbers. Big one and easy to spot and fix. All AM towers need to have a locked fence around the base insulator. Any tower over 200 feet tall needs to be registered and have a sign with the registration number posted. The sign needs to be accessible and legible.

So prepare ahead of time for the inevitable visit. It is very easy to comply with the FCC rules using the FCC checklists. Both the AM station checklist and the FM station checklist can be downloaded and used to self-inspect any radio station.

Here is something else that I have found. Clean up the transmitter site. Sweep the floor, replace the burned-out lights, empty the garbage, keep a neat maintenance log, etc. These things go a long way to making a good first impression, which can make the inspection go a lot better.

Once, I and the FCC inspector pulled up in front of the transmitter building of an AM station. The grass in front was mowed, the bushes were all trimmed back, the field was mowed, the towers had new paint on them, The fences were in good shape, and the place just looked good. We were about to go inside when he asked “Does the inside of that place look as good as the outside?” Which it did and I said yes. Then he said he had seen enough, have a nice day.

So, when the FCC guy shows up, offer him a cup of coffee and relax, things are going to be alright.

Update: This is the actual checklist that an FCC inspector will use if he is inspecting a broadcast station.

You can download the .pdf version here.

About community radio

Because of this post, I have received some e-mails asking why I am against community radio. I am not. In fact, I support community radio. I think that community radio done well is a wonderful tool in our democracy, giving a voice to those that are watching the government. It also promotes other locals’ interests, events, music, etc. I would like to see more failing stations bought by community broadcasters and turned into something that is a public trust and responsive to the local population.

What I was trying to get at in the previous post was that overcrowding the FM band with more and more small signals will degrade it. There are no ifs, and, or buts, removing third adjacent protections on the FM band will increase the noise floor. This will lead to more interference on the average FM radio, which will lead to more people getting fed up and tuning out.

Here is why: You cannot change the laws of physics. FM transmitters have output filters that attenuate sideband energy, that is to say, energy transmitted on 1st, 2nd, and 3rd adjacent channels. A 50,000-watt FM station on 100.3 MHz will have sideband energy on 100.1, 99.9, and 99.7 MHz as well as 100.5, 100.7, and 100.9 MHz. Due to the limitations of the components used to construct those filters, they can only be designed with the accuracy of the components used. In other words, most electrical components have a tolerance given in percent, for example, +/- 10%. That means that the value of the component will change, usually because of heating. Therefore, output filters cannot be constructed to limit emissions to only the main channel and say one adjacent channel, they would drift off frequency.

Also, creating a brick wall filter that cuts everything off at the second adjacent channel will cause distortion of the RF signal on the main channel. With analog AM and FM transmitters, it cannot be done. Digital transmissions are another story, but that is not what we are talking about here.

That is an engineer’s point of view.

One other thing about adding hundreds more LP FM signals. There should be something that stipulates most (say >50%) of the programming be locally originated. Recorded for later playback is fine. Having thousands of LP stations broadcasting the same syndicated shows or running voice-tracked automation 24/7 would be a recreation of the AM band as it currently exists. If you want to listen to that, then it already exists, help yourself. I, on the other hand, would like to avoid the AMization of the FM band.

That is all.

Working with Tower Companies

Almost all radio stations use a tower of some sort to support their transmitting antennas. These towers need maintenance from time to time and only qualified people should perform maintenance on towers. Hence, the tower company is formed.

405 foot guyed tower with ERI FM antennas

Over my years of experience, I have dealt with many different tower companies, from one-man operations to big corporations that have multiple crews out in the field on any given day. I have discovered that not all tower companies are created equal. Not only do tower climbers need to be in good physical shape and be trained correctly in all tower climbing safety procedures, they also need to be good mechanics so they can actually repair things on the tower. Climbing a 470-foot tower to repair a strobe light is all well and good. Once the climber gets to the strobe light, he needs to be able to disassemble it without dropping parts or breaking things, troubleshoot if needed, install new parts, and re-assemble the unit, again without dropping or breaking anything.

Applying RF connectors, installing an FM antenna or STL antenna, and repairing light fixtures or conduit all require some amount of manual dexterity and concentration. Assembling high-powered antennas requires close attention to detail. Any pinched O rings, cross-threaded bolts, bent bullets, and the antenna will have problems, likely at the worst possible time.

The sign of a bad tower company is if its climbers cannot carry out those tasks with one or at most two climbs. I have a situation on a tower where our FM station is a tenant. The tower has a strobe light failure near the top of the tower where our FM antenna is located. They have climbed the tower no less than four times to repair this, and it is still not fixed yet. Each time they climb, the station has to reduce power to protect the tower climbers from excessive RF exposure. Each climb it takes them several hours longer than anticipated to finish their work.

A good rule of thumb, If the defective part cannot be fixed in the first two climbs, then the entire strobe unit should be replaced on the third climb. Even though the strobe units are expensive, by the time they get done paying for all this tower work, they could have bought two new strobes. Today will be the fifth climb and there is no guarantee that it will be fixed.

I advised the tower owner that they should be looking around for another tower company because these guys aren’t exactly setting the world on fire.