Follow Slashdot blog updates by subscribing to our blog RSS feed


Forgot your password?
DEAL: For $25 - Add A Second Phone Number To Your Smartphone for life! Use promo code SLASHDOT25. Also, Slashdot's Facebook page has a chat bot now. Message it for stories and more. Check out the new SourceForge HTML5 Internet speed test! ×
Open Source

Video David Klann Talks About Using Open Source Software in Broadcast Radio (Video) 35

David Klann works with Driftless Radio, call letters WDRT, in Wisconsin. This is community radio, with no huge advertisers or morning shock jocks with names like Bobba the Fet Sponge. They use open source software for just about everything except accounting, and that includes processing their audio for both OTA (Over the Air) and online streaming. Their transmitter runs a "stripped down" version of Debian, and David is proud that they had 3 1/2 years of uptime -- that only ended when David did a kernel upgrade that forced a reboot. (Alternate Video Link)

Tim Lord: David, what is community radio and how did you first get involved with that?

David Klann: Yeah, that’s a great question. There are lots of different kinds of radio stations out there, the most common of course is the commercial radio station where they sell time. It is kind of like with Google the product is not the Gmail the product is you—the user. In radio, the product is the listener. And then there’s public radio. In my home state, we have Wisconsin Public Radio, there’s National Public Radio. And then there’s community radio. Community radio stations are typically independent. They are typically run almost completely by volunteers. Ours has three part-time paid staff members, and the rest of the station is run by volunteers.

Tim: Tell everyone the name and the frequency of your community radio.

David: Oh sure. The radio station that I am associated with is WDRT. It is in the Driftless region of Wisconsin and we are on 91.9 FM and

Tim: How big a radio does that actually take in?

David: Compared to some it is a small station. We are 480 watts and we cover about a 25-mile radius around the tower. So it is a pretty small geographic footprint but we like to think that we are making a huge impact in the community.

Tim: Running a radio station is a lot different from people doing person-to-person communication, as in HAM radio.

David: Yeah, right.

Tim: What are some of the complications? What are some of the equipment that you use for instance? How do you get a signal from soup to nuts, how do you actually put a signal out on an FM station?

David: Sure. I think the main thing is that the FCC is heavily involved. I think it is partly because these things are such high powered. Even at 500 watts we are far more powerful than a lot of HAM radio outfits and certainly more powerful than the old CB radios, more powerful than the cell network, individual radios on the cell network, I think partly because of the large power output and also because of the limited spectrum that was originally allocated for FM radio. Radio stations, unlike other over-the-air wireless communications, radio stations first of all, they are one way. It is all being sent out from a source. So at our station—and this is pretty typical of radio stations—we have all the input devices, microphones, turntables, tape players, CD players, computers, iPods, whatever people bring to the station, all that gets funneled through what we call the audio chain. At some point, right before it leaves the station, we digitize it, and we send it to two places: We send one half, not really half, but we send one copy of it up to the transmitter. We use a leased Ethernet line for that. And then we send another copy of it out to the stream on the internet. And so our internet stream, and our FM broadcast are identical. In the chain from the studio to the transmitter, you’ve have got an encoded piece of audio that gets sent up over the Ethernet. At the other end, at the transmitter end, it gets decoded—it turns back into analog audio and then is sent to the transmitter just via coaxial cable.

Tim: You are using open source software to control that entire chain?

David: Yeah, all the way up to the transmitter and actually including the transmitter, all the software is open source—we are using Liquidsoap to do the encoding and the decoding. For audio production, we are using Audacity as the audio editor. A lot of people use Audacious to play. We use an open source automation system called Rivendell that does it. We don’t staff 24 hours at our station and so for the overnight hours, where we are not staffed, we do automated playlists—that’s done with Rivendell. What else? Well, you mentioned the open source chain. The open source actually extends into the transmitter.

Tim: Explain that a little bit.

David: Yeah. It turns out that the manufacturer of our transmitter, Nautel, is based in Nova Scotia. They started out doing marine radio. So they do really hardened stuff. They put radios out on buoys and it had to last a long time. They’d gotten into the broadcast space, and they chose to put a computer inside their transmitter. And the computer runs Debian. It is an ARM processor. It runs Debian distribution. But they’ve stripped it way down, it is highly customized but you can get a shell on it. It is pretty cool to poke around.

Tim: You’ve had to upgrade that?

David: Yeah. In fact, our transmitter had an uptime of three and a half years. The Debian instance was running for three and a half years until about a month ago. I put an upgrade on it, and they upgraded the kernel and so it forced a reboot.

Tim: How is it like, if you’ve have got a radio station that is running even unattended, do you have to do anything special to do you need to put a bank of UPSes on all your equipment to make sure things stay up overnight—how concerned are you about that?

David: Yeah sure. Well, it is a kind of a two-part answer. The first part is yeah, it is just like any other instance of a computer or a set of computers where you want high availability, we use UPSes kind of consumer grade UPSes because we are a community station with a low budget. But up at the transmitter, we are in a commercial grade data or transmitter shack up there. So we’ve got UPS on the transmitter itself and the audio decoder. And it is also backed up with a generator. So we’ve got a good power supply up there in the studio.I like to say it is community radio and people kind of expect that things will break once in a while.

Tim: Now in talking about the software you use, you mentioned Rivendell and you mentioned Liquidsoap, you mentioned using Icecast, where does Icecast come in the picture?

David: We send the encoded audio out to the streaming server via Liquidsoap, and then on the streaming server, we split that stream into three pieces:one for high bandwidth users, one for low bandwidth users and another one for folks that want to use the Ogg Vorbis. The high and low are MP3 which is pretty common. We also want a supply stream for the folks that love open source codecs and so we use the Ogg Vorbis codec. That’s also a high quality codec. So we split it into three. Those three streams get sent to Icecast and Icecast is what makes the audio available to the listening public.

Tim: You are using Linux as well even in the administrative functions within the station?

David: Yeah. Every computer except one at our station is running Linux. Most of them are Debian installations. Automation system runs Gentoo because of the customizability that we can get with Gentoo. So the Rivendell stuff runs on Gentoo and pretty much everything else runs on Debian, we run Wheezy I think for just about everything at this point.

Tim: What’s the exception about the machine that’s not running Linux?

David: Our accounting system. Our bookkeeper uses Quick Books. We are actively searching for open source accounting, and so we would love to hear opinions on that. I know that that’s a common thread on Slashdot and other places as well.

Tim: You mentioned Rivendell, the automation function that it had, and I know you also have a project that is related to that. Can you talk about that a little bit?

David: I and one of the other volunteers at the station have started a little project called Open Source Radio. It is What we are trying to do is basically put an entire specification together for open source radio. Recently the FCC granted construction permits to thousands of low power FM radio stations—they are even more strapped for cash than we are. So what we are trying to do is put together sort of a recipe for building a radio station at varying cost levels. The bottom one starts at about $500 where you can just build basically a radio station in a box. And then it goes up from there, and you can add components and pieces to it, and spend pretty much as much money as you want. I spent about $80,000 to $90,000 putting our radio station together. Some of it was new equipment. The transmitter we bought new. Some of the computers I bought new. Some of them were refurbished from donations from area businesses and stuff like that. So you can really spend as little or as much as you want. One of the things that we are working on right now is a super low latency—hopefully zero latency—compressor limiter that is all open source codecs, all open source stripped down operating systems, real time kernels that kind of thing. We can buy something like that out on the open market for as little as $1600, we can make that for cast off equipment and open source for fifty bucks. So that’s the kind of thing that we want to achieve with open source radios. Make this achievable for LPFMs, people that want to do webcasting, or full power radio stations. So that’s the goal with open source radio.

Tim: When you bought you transmitter that does run Debian in kernel, did you shop for them that way, did you look for an open source transmitter, or is that just the luck of the draw?

David: It was luck of the draw. Nortel has gained a really good reputation in the broadcast industry and it was affordable enough for us that we could buy that one and there’s probably I don’t know half a dozen well-known brands of broadcast transmitters. Everybody recommended Nortel to us and I did the specs and went through all the review of the specifications and I settled on that one. I am really glad we did.

Tim: David, let me ask one more question: You are in a cold state at least for someone like me living in Texas right now.Do you have any equipment horror stories that are in this type of weather that your station has to weather very much?

David: Oh man! You know, our antennae has these covers on them, I think it is PVC covers called radomes and we’ve survived four Wisconsin winters so far. That’s been okay. Unfortunately, I can’t think of any weather related horror stories.

Tim: That’s unfortunate for me.

David: I know but stories are always great.

Tim: I know. I’d like to ask one more now. If people want to learn more about community radio, and they are intrigued by the concept, where would you advise them to start looking, because I think a lot of people want to do college radio and things like that.

David: Yeah, yeah.

Tim: It is not an opportunity you see everyday.

David: There are tons of resources. I would search for well, you can go to our wiki, We have put up a lot of our founding documents, our bylaws, our planning documents and things like that—it is pretty typical. Another really good place is They have got tons of good resources that they publish and references to other folks that do community radio. Just earlier this August I attended the Grassroots radio conference, I think their website was And they’ve also got references to a lot of other really good resources out there.

Tim: It sounds like a fun community.

David: Yeah, it really is. It is grassroots and down to earth people doing good work. It is really fun to be associated with them.

This discussion has been archived. No new comments can be posted.

David Klann Talks About Using Open Source Software in Broadcast Radio (Video)

Comments Filter:
  • by Anonymous Coward

    This is AC This is AC please come in

  • by UnknownSoldier ( 67820 ) on Tuesday September 02, 2014 @04:18PM (#47810415)

    ... means just asking to get hacked due to not keeping up-to-date with patches.

    This is the '90's anymore.

    • You are thinking of Windows. With Linux most updates happen without the need for a reboot. The only kernel vulnerabilities you are likely to be exposed to are privilege escalations, in which case they have already hacked in to the system. I'm not saying it isn't a good idea to keep current, but using an older kernel is far from the same as not applying updates for three years as you seem to be assuming it does.
    • by jandrese ( 485 )
      Nothing is more 90s then having to reboot just because you applied a patch to an application. The only thing you should need to reboot for is kernel upgrades, and it seems like that is exactly what happened here.
    • by OzPeter ( 195038 )

      ... means just asking to get hacked due to not keeping up-to-date with patches.

      This is the '90's anymore.

      To be fair he was talking about the embedded debian installation built into the transmitter hardware, not some general purpose surf the internet type thing.

  • If you want to use a real world example but don't want to say Bubba the love Sponge, there's always Howard Stern or Mancow or Bob and Tom or a host of other clean shockjock names...don't just make stuff up, it takes away from an otherwise interesting summary.

  • To David Klann for using Open Source, for keeping huge advertisers at bay, and for servicing his community. There's a clear signal there in Wisconsin.

  • It's great to see how others utilize open source software. Last year myself and some friends started MT Radio.Net []. We are Community Internet Broadcasting, showcasing Montana talent and more. Staying away from FM/AM transmission allows us to operate uncensored with material that is sometimes explicit. Importantly, it has allowed us to begin broadcasting with very little overhead or financial investment. With donated microphones and mixing consoles and many hours programming, our NEW Player (beta) [] is now up

  • Hmm, the transcript says 'Nortel' but it's actually 'Nautel'. They make good transmitters, and have for a very long time.

  • open source software windows []
  • I don't see how a radio station in the United States can steam over the Internet using exclusively free software. Apple iOS devices play only MPEG codecs subject to royalty-bearing patents, not any free lossy codecs. And HD Radio in the United States uses an iBiquity codec parts of which are patented and parts of which are trade secrets [].

    Spell check turned iBiquity into Iniquity. Telling?

    • by tlhIngan ( 30335 )

      I don't see how a radio station in the United States can steam over the Internet using exclusively free software. Apple iOS devices play only MPEG codecs subject to royalty-bearing patents, not any free lossy codecs. And HD Radio in the United States uses an iBiquity codec parts of which are patented and parts of which are trade secrets.

      There are free software implementations of MPEG4/AAC encoders (faac, for example). It's free software by any means because the user is free to do anything with it. Usage in

FORTUNE'S FUN FACTS TO KNOW AND TELL: A giant panda bear is really a member of the racoon family.