Hack19.Tune Your PC for Radio Reception

Hack 19. Tune Your PC for Radio Reception

With the right receiver, your PC can take over the radio function of a car's head unit.

Receiving radio broadcasts via home PCs has always been somewhat of a novelty option. Every generation of PC has had its tuner cards or external USB receivers. But as radios already do a great job of receiving broadcasts, it's only the added featuressuch as remote control and timed recordingthat make PC radios valuable. Now you can take advantage of these features with your car PC, too.

2.9.1. PC Radios

There are two basic kinds of PC radios: external radios connecting to USB or serial ports, and PCI cards with FM tuners on board. Almost all of these cards output analog audio via a pair of cables and use the USB or PCI connection only for tuning the station. There's no real point in sending audio over a digital connection, because the broadcasts are analog to begin with. Instead, the audio goes into the CD-in, line-in, or microphone input of the computer's sound card.

Every computer radio comes with software that allows you to control the tuner, select different channels, and display which channel you are on. None of these applications, however, are designed for in-car use; they are generally quickly-thrown-together Windows programs that do a rudimentary job of tuning and may or may not offer extra features such as timed recording, pause, and so on.

2.9.2. Problems with PC Radios

Radio is one of the most difficult responsibilities for the PC to take over. For one thing, head unit radios are very mature and sophisticated, and they are designed to clearly receive broadcasts while moving at highway speeds. PC radio cards and USB receivers, on the other hand, usually use the cheapest radio chip available and are designed to sit still on a desk or in a window. This means that the signal quality of these devices is not as high as it could be.

Another problem with PC radios is that they do not adhere to a standardized programming interface. Each new unit from a different manufacturer has its own method of changing stations, and these aren't usually part of a published API. Luckily, the interfaces usually get reverse-engineered by the Linux community to produce open source drivers and documentation, but this does mean that in-car GUI software has to be re-coded to control each different FM receiver.

Finally, most of the PC card and external radios do not pick up AM signals. While not that important for the desk-bound target market of the devices, lack of AM radio is a showstopper for many drivers.

2.9.3. The Hack: Getting Radio to Your Car PC

In 1999 D-Link came out with an excellent FM radio tuner, the DSB-R100, that was easily controlled by USB. There are now many third-party applications that can control that unit, because it's been around so long. You can still buy them on eBay and in car computer forums such as http://www.mp3car.com. A company called Radio Time (http://www.radiotime.com) bundles an almost identical unit with their subscription service, and Griffin Technology makes the Radio Shark (http://www.griffintechnology.com/products/radioshark), which works on Macintosh computers but may have third-party drivers for Linux by now. A number of PCI TV Tuner cards also include FM tuners. Hauppauge (http://www.hauppauge.com) makes several different inexpensive PCI and USB TV and FM tuners.

Whatever radio tuner hardware you find, it's probably going to be supported by Radiator (http://www.flesko.cz), a freeware program for tuning and recording radio from any PC radio device. In fact, you can find a rather complete list of the radio tuner hardware available for PCs at the Radiator web site. Radiator is probably the best program for car PC useit's supported by car PC frontends such as CENTRAFUSE [Hack #73] and FrodoPlayer [Hack #75].

If you must have AM your options are limited, but you will find that there are more expensive scanner units (costing several hundred dollars) that pick up AM, FM, and a variety of other signals, such as police and emergency frequencies, and are controllable by USB. You can have it alljust not on a shoestring budget.

Once you have chosen an FM tuner, you need to route the antenna from your car to the antenna input of the device, or your reception is going to be pitiful. For this you need an antenna splitter that allows you to tap into the antenna while still letting it go to your head unit. The most useful of these splitters are called scanner splitters (Figure 2-14), because they're designed to split the antenna signal out to a scanner. These usually have a standard BNC connector on the end.

Figure 2-14. A scanner splitter for an antenna and its connector cables (courtesy of http://www.walcottcb.com)

Once you have this antenna connection, it needs to be adapted to the antenna input of your tuner. Tuners usually accept either a U.S. television coaxial male connector (Type F) or, less usually, an RCA-type input. Radio Shack carries a BNC-to-coax adapter, as well as RCA, BNC, and coax adapters.

If you don't want to buy all of these adapters, or you are getting rid of your head unit altogether [Hack #15], you should be able to just splice and solder the correct connector onto your radiosimply take a piece of coaxial cable (for television), and solder it to a simple FM splitter. You don't want to start cutting up the cable that runs your antenna to your car stereo; it's always cheaper and easier to destroy a $10 part in the process of hacking than to explain to the dealer why you need a new antenna wire run through the body of your car.

Once you get this antenna linked into your receiver, you should get better reception than you ever did with the receiver in the house. Your car PC now has the potential to replace your head unit's radio, especially if you take advantage of the car PC frontend software that we cover in Chapter 7, such as FrodoPlayer.

2.9.4. PC XM Radio

The success of subscription satellite radio in the U.S. is either strong evidence of consumer interest in audio entertainment, or strong evidence that traditional radio sucks. In either case, satellite radio services such as XM and Sirius are getting more popular every day, and most new car head units are satellite-ready.

For a while, the hardware cost for satellite radio was very high, and you could easily spend almost $400 to upgrade to satellite radio. In the last year tuner hardware prices have plummeted, and the basic XM receiver (called XM Direct) now costs less than $50, and can be used with any XM-ready stereo head unit.

What's more, with a simple cable you can build for about $15, you can turn your own car PC into an XM-ready head unit! You can find a schematic for the appropriate cable at http://www.i-hacked.com/content/view/56/94/ (or just Google for "XM Direct PC Cable"). Using these inexpensive cables, most of the car PC frontends (see Chapter 7) include the ability to tune XM radio.

If you don't want to build, you can buy premade homebrew cables for about $25 on the forums at http://www.mp3car.com, or you can buy hardware and software from TimeTrax (http://www.timetraxtech.com). Their software not only connects the XM Direct receiver to your computer, but also allows you to do scheduled recordings [Hack #20].