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What’s the Deal with LPFM and HD Radio?

Our latest podcast is all about the first, and—to the best of our knowledge—only low-power FM station broadcasting digitally with HD Radio. The episode has stimulated quite a bit of conversation on social media and raised some questions about the relationship between LPFM and HD Radio. Here I’ll try to answer the most common questions and clear up some of the confusion.

The station we profiled is KVCB-LP, a high school station operated by Vacaville Christian Schools in Vacaville, CA. Ralph Martin, the operations director, contacted us months ago to let us know about his experiment in broadcasting in HD Radio. For those who are unfamiliar, HD Radio is a digital broadcasting standard that works on the analog AM and FM dials, allowing stations to add a digital signal that can carry one to three channels of programming.

Because the digital signal is a sideband to the primary analog transmission, it expands the amount of space a station takes up on the dial (a reason why critics oppose the technology in the first place). To mitigate the effect this has on adjacent stations, the digital HD signal can broadcast at no more than 10% of the station’s rated power. So a 10kw station can have an HD signal broadcasting at no more than 1kw.

A LPFM station, then, which is limited to 100 watts, can have an HD signal with no more than 10 watts of power. But, as Martin explained, that isn’t the primary barrier for LPFM stations to broadcast in HD. What he found is that there simply aren’t any LPFM-approved transmitters available for HD.

You see, HD Radio requires a specialized transmitter. It’s not just some kind of add-on, like a signal processor. But HD Radio transmitters are designed for full-power stations, presumably because manufacturers—correctly—presume there is very little market amongst LPFM stations.

As he explains on the podcast, Martin eventually found a LPFM transmitter model that is similar to one used for translator repeater stations, that can have an HD module added to it. Essentially, putting KVCB on air in HD required some hacking, with willing assistance from the manufacturer.

Although KVCB’s HD signal is only 7 watts strong, Martin tells us that the signal is about as robust as the analog signal, often coming in better in places where the station’s analog signal is weak. In addition to the main HD–1 digital signal, which is required to simulcast the station’s primary analog signal, KVCB broadcasts HD–2 and HD–3 channels with alternative programming, with all student-created programming on HD–2, and HD–3 broadcasting school information.

Should LPFMs Go HD?

The question we’ve been hearing since releasing the podcast is: Is HD Radio a wise, or even necessary, investment for LPFM stations? Based upon the scant evidence we have so far, it’s hard to make that case.

Martin told us that one of his motivations for doing the interview is to network with other LPFM stations interested in HD, with the goal of convincing equipment manufacturers to make the necessary transmitters. While my intention is not to oppose his goal, I have to honest in my assessment.

Frankly, it’s even tough to make a strong argument for a full-power station to adopt HD Radio. Home HD Radios are rare. Most HD Radio receivers are in cars, where listeners are often unaware of the fact that they’re listening to a digital signal, as their radios seamlessly shift between analog and digital signals, depending on what’s stronger.

Sure, there are the additional HD–2 and HD–3 channels, but these aren’t easy to scan like analog stations. It takes a few extra seconds for an HD receiver to lock on to the digital signal and then find the HD–2 or 3 channel. Doesn’t sound like a lot of time, but when you’re used to the near instant tuning of analog stations, a few seconds is an eternity. In practice, this means the the driver scanning the dial on her HD-capable car radio will only occasionally stumble upon an HD–2 or HD–3 signal.

Of course, if you know about an HD–2 or HD–3 signal that you want to tune in, you can do that. But, really, how many HD–2 or HD–3 stations do YOU know about? If you have an HD Radio capable radio in your car—and you know it’s HD capable—how often do you seek out HD–2 or HD–3 signals?

So, if HD Radio is a questionable investment for a full-power commercial station, it’s an even dicier proposition for a non-profit, non-commercial LPFM. The big question is: How will HD Radio enhance an LPFM’s service?

Though having one or two additional channels to program is enticing, as it is, plenty of new LPFMs have a hard enough time filling all 168 hours of the broadcast week for their main channel with fresh, live programming. How do they expand to 336 or 504 hours?

An even bigger question is: How many people in your community have HD Radios, and use them within your broadcast radius?

If HD Radio were an inexpensive technology, these questions would still be relevant, but would constitute speed bumps rather than roadblocks. But HD Radio is not cheap. As Martin explained to us, the one transmitter that can be modified for HD costs between $5,000 and $8,000—more than most LPFM transmitters.

Plus, most new LPFMs are already on air. So, going HD would require replacing their current transmitters wholesale.

On top of equipment costs, HD Radio is a patented and licensed technology. Unlike analog FM tech, it’s not free to use. Stations pay a licensing fee to adopt HD Radio channels, and then an annual fee for digital sub channels.

Unfortunately, we didn’t get into this free structure with Ralph Martin in our interview. So I’m not certain on how much a noncommercial LPFM would be expected to pay, given that the annual fee is based on 3% of revenue.

But any additional fee is a burden for many LPFMs, whether it’s the money or the additional paperwork.

As it is, I can’t advocate for your average LPFM to adopt HD Radio technology. For most stations, I simply can’t see how it would enhance their local service enough to justify the additional cost and complication.

That said, if you’ve got the money and the time to mess around with it, I can’t make a strong argument that it’s an utter waste. Rather, it’s best considered an experiment, in that the results and impact are unknown. It may be that listeners in your community are ready to take advantage of an HD signal and any sub channels. But that’s a question only the broadcaster can answer.

If you’re interested in learning more, you’re invited to reach out to Ralph Martin at KVCB.

What About These LPFM HD-2s I Hear About?

It’s not uncommon for commercial and non-commercial stations that use HD Radio to rent or lend out their HD–2 and HD–3 signals to other broadcasters. As we’ve reported, in some cases an HD–2 signal on another station has been offered up as a consolation prize to college stations that had their licenses sold, making them otherwise internet-only.

In other cases there are LPFMs or small community stations that also broadcast on a larger station’s HD2 channel in order to reach a somewhat wider audience. A more common use is to feed a translator repeater station that extends the station’s reach.

As Michelle Bradley of REC Networks informed me, it’s legal for LPFMs to own and operate up to two translator stations, but those repeaters are limited in how far away they can be sited; generally between 10 and 20 miles away, and the repeater must be fed by the LPFM’s over-the-air signal. But if a full-powered station’s HD–2 channel is used to feed the translator the repeater doesn’t have to be limited to the low-powered station’s broadcast area–it only has to be within reach of the broadcast area of its higher-powered host.

But it’s important not to confuse a LPFM that is rebroadcast on a larger station’s HD–2 as the same as the LPFM having a HD Radio broadcast itself. It’s more like an AM station that gets onto the FM dial by leasing some HD–2 space on an FM station. It has nothing to do with a LPFM actually getting an HD Radio transmitter and broadcasting in HD.

Isn’t HD the Future?

In our interview Martin tells us that one of the reasons he looked into HD Radio is to sort of future proof the station, in the eventuality that it becomes the radio broadcast standard in the U.S., in the same way that digital broadcasting replaced analog on television in 2009. Though not impossible, a digital radio transition is not likely in the near future.

For perspective, note that the digital television transition required an act of Congress, paired with a subsidy so that Americans could buy reduced price converter boxes for their analog TVs. Moreover, digital TV offered a very obvious and visible upgrade, by supporting a high definition picture with four times the resolution of analog broadcast.

While the “HD” in HD Radio implies that it’s somehow “high definition,” the same quality upgrade doesn’t quite apply. Digital HD Radio signals are not susceptible to noise and interference like analog signals, but the quality difference between a HD Radio signal and good analog reception is minor in most cases. The addition of more channels per stations qualifies as an upgrade of sorts, although as someone who regularly surfs the HD–2 and HD–3 signals, it doesn’t seem like most broadcasters have figured out any profitable purpose for them.

HD Radio was sold to the FCC based upon its ability to work alongside analog signals, to supplement, rather than replace. It seems as though there was not, and is not, much of an appetite to transition the country to an all-new radio standard, obsoleting millions of receivers in the process.

I suspect it would require a similar act of Congress to transition the nation to digital radio, and I frankly don’t see that happening. Mostly because I don’t see the broadcast industry lining up in support, seeing little return on investment for the massive infrastructure upgrade. Plus, there are millions more radios out there than televisions, with the most valuable ones (from a broadcaster’s standpoint) installed in cars, where they are less likely to be upgraded. Instead, a driver with a newly obsolete radio would probably just switch to her smartphone.

Therefore, I don’t see HD Radio as a strategy for future-proofing. Even in the unlikely event of a digital radio transition, stations will get years—if not a decade—of notice.

LPFM + HD: A Valuable Experiment

I’m grateful to Ralph Martin and KVCB-LP for experimenting with HD Radio and low-power FM. We’ve always relied on the tinkerers and experimenters to push radio forward.

Frankly, I was surprised to learn from him that KVCB’s HD signal is nearly as strong as its analog signal, even at 7% of the power. It goes to show that we can’t necessarily generalize based upon the performance of a 10 kilowatt transmission to a 100 watt transmission; not everything is linear.

Even if HD doesn’t gain traction in LPFM, Martin and KVCB have contributed useful findings to our knowledge of the medium, and have valuable experience and tips to share for any stations that want to try out HD.

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3 Responses to What’s the Deal with LPFM and HD Radio?

  1. vcsradio June 9, 2017 at 9:47 am #

    Paul has some great points as always — and I certainly would agree that any LPFM station operator consider strongly their resources before going headlong into HD Radio… But consider this:

    The key difficulty is getting the equipment to work with the maximum digital power allowed — especially with many LPFM antenna systems that require a lot of output power. These capable transmitters are available right now, they’re just not LPFM certified as yet so we can’t use them. A manufacturer only needs to get a higher powered transmitter certified so LPFM operators can easily plug-and-play HD Radio technology. LPFM operators simply need to speak up. Let the industry know our interest is there. Remember we LPFM’ers are thousands in number! That’s why this conversation is so important! They’ll listen to us!

    With HD Radio, you don’t really have three separate radio stations and you shouldn’t look at it that way. You have one station with increased options. Paul said it’s harder to tune in HD2 and HD3. Well — I guess — maybe. Our listeners go to 100.9 and listen to our home channel — then if they want, they can go to our “menu” and select another channel and listen in. It’s kind of like going to Radio Survivor’s web page and then clicking on one or their additional menu items. Not that hard.

    Equipment packages will continue to go down in price especially if manufacturers know LPFM has an interest.

    Right now, the licencing fees are greatly reduced for LPFM. licensing the sub-channel capability is a $5,000 one time fee that can be split up into yearly payments over 5 years interest free. No continuous fee charges.

    I can only convey my own experience and it was positive. We have no problem programming three channels and we do get great community support — even for HD2 and HD3. The FCC was very helpful. The manufacturer was very helpful. DTS was extremely helpful! For us, it was definitely worth it.

    Having said that — LPFM is a very diverse community and the needs are unique to each station. What I know is that LPFM shouldn’t be left out of the digital conversation. Dream! Consider! Talk about it! Listen with an open mind. Paul’s right — we have time. It’s not bad to consider LPFM’s place in the digital realm.

    Feel free to reach out if you have any questions. I love to talk shop

    Ralph Martin

  2. kthelen June 10, 2017 at 5:28 pm #

    What I really wanted to know was what this mystery transmitter was, since it’s only mentioned in vague terms. My first thought was Nautel, but the mention of an HD “module” tripped me up a little.

    It took several minutes of listening (and skipping around) to finally hear Mr. Martin recite the letters and numbers I was expecting to hear from the very start: “VS300” – or, more likely, VS300LP (the LPFM certified version).

    Even more details, for the technically curious:

    Sounds like a Nautel Importer/Exporter, VSHD exciter, and a VS300LP, feeding a Jampro JLCP-2. Pretty slick!

    Of course, I figured they’d have to be in a pretty populous area for this to be anything more than an expensive toy. Quote from above linked thread: “our 60 dbu contour covers about 93,000 people”. Okay, I get it now.

    Another quote: “The kids want extended hybrid. I’ll do my best for them” – if there are high school kids out there that can discuss the merits of Hybrid vs. Extended Hybrid, -14dB vs. -10dB, etc., then maybe there’s hope for the future of broadcast engineering 🙂

  3. vcsradio June 11, 2017 at 4:51 am #

    kthelen, The cat’s out of the bag!! 🙂

    Transmitter: Nautel VS300LP — The internal exciter had to be deactivated and bypassed, so some internal soldering and breaking out ferrite shielding was required — and a shop vac to remove any ferrite dust in the process. Fun, but a bit scary in an expensive transmitter. Also the Orban processor is lost as well, so external processing is required. The transmitter can still handle some modulation protection and will still handle pre-emphasis, thankfully.

    External Exciter: Nautel VSHD with Broadcast Tools A/D converters as it requires digital audio feed our studios feed analog.

    Nautel Exporter Plus — for also required A/D converters to feed HD1

    Nautel Importer Plus — to feed HD2 and HD3 — oddly enough, accepts analog audio feeds.

    Audio processing for Analog and HD1 — Claesson Edwards’ Breakaway Broadcast One (PC based)

    Audio processing for HD2 and HD3 — Orban 1101PC (included with Importer Plus)

    Special note:
    Audio processing is a real challenge for us as our programming is so diverse and the program sources come from kids who are not always as audio-conscious as they should be. We’re also fighting to “conform” to the commercial band where stations brick-wall their audio. Also, because our listeners’ cars often leave our service contour I have to match our audio to our co-channel neighbor so when ducting occurs they don’t blow our listeners out of their cars when their radio intermittently “locks” (an FM analog thing) onto their signal (a fact of life for LPFM).

    Antenna — Jampro JLCP-2 — 2 bay — full wave separation to allow for 129 watts analog TPO. The transmitter can supply 130 watts so it just barely makes it. At -10db the transmitter falls short with only 120 watts available, so no go on that one :/ The Nautel VS1 could handle the 274 watts into our single bay — no problem except it’s not LPFM certified, so can’t use it. See the problem?? Simple solution — Nautel, please get your VS1 transmitter LPFM certified. I’m sure the FCC will understand its purpose.

    EAS — a former student – now a systems control engineer — designed a multi-channel audio relay box for our Gorman EAS1 and DEC1 CAP-to-EAS converter so one EAS unit interrupts and feeds all HD Radio channels.

    Oh my… LPFMers, don’t let this all intimidate you! I’m a music teacher, I got through it okay.

    Broadcast engineers: reach out to your local LPFMers! They’re broadcasters ready to serve the public at a hyper-local level and will ultimately keep radio interesting and vital for everyone on the spectrum.

    Ralph Martin

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