Building a Nationwide Low-Cost Wireless Digital Communications Network for Portable Devices

by Stewart Teaze, N0MHS


Are you interested in accessing the Internet from your laptop or PDA, but DON'T want to pay an arm and a leg for equipment and outrageous monthly fees? If so, read on...

Up until recently, the only low-cost wireless digital communications systems have been based on low-speed Amateur Packet Radio equipment. However, inexpensive High-Speed Wireless Networking is now possible using Part 15 devices. Many of these devices work in the Amateur Radio Service bands, and Amateurs are allowed to modify them for greater communication range than is acheivable under the FCC Part 15 regulations.

Low Cost Wireless Network How-To
Wireless LAN Project
Down East Microwave
VHF/UHF/Microwave Radio Propagation: A Primer for Digital Experimenters
Green Bay Professional Packet Radio
Using Part 15 Wireless Ethernet Cards For Amateur Radio
FCC Part 15 Devices
Range of Part 15 Devices

However, There are a number of problems with this approach:

A) Part 15 devices have severe range limitations.

B) Amateurs are allowed to increase the range of these devices by modifying the antennas and transmitters; but under Amateur rules, commercial content is verboten. Using Amateur Radio, you can't conduct business, or download web pages containing advertisements.

C) Part 15 devices are not currently suitable for laptop or PDA applications.

The FCC is working on converting the frequency space currently allocated to UHF Television channels 60-69 to a new service that would be specifically targetted to Portable Wireless data applications. However, the current "squatters" aren't going quietly, so we may not see such a system like this in the United States for another 5 years. Besides, these frequencies are likely to fetch $100 Billion dollars at auction time - so the service won't be cheap.

If you are able to live with a fairly slow data transmission rate, a packet radio-based system may be be just the answer. The FCC has recently approved a new, unlicenced personal radio service that allows digital communications - the Multi-Use Radio Service(MURS). By using the old packet radio technology first developed in the 80's, updating it for the 21st century, and using it on the MURS frequencies, you can have access to e-mail, chat, stock quotes, newsgroups, and many other applications - and NOT have to spend a lot of money to do it.

Multi-Use Radio Service (MURS)


TAPR and Amateur Radio Network History

Tuscon Amateur Packet Radio(TAPR) developed the 1200bps Terminal Node Controller(TNC) during the early '80s. They licensed the technology to commercial companies, and it formed the foundation for a gigantic network of Amateur Radio Stations that developed during the 80's and early 90's. At the time the original TNC was developed, 1200bps was actually better than landline modems were achieving at the time. Unfortunately, TAPR hasn't done much since then.

When landline speeds began to climb during the 80's, it did not affect the growth of the Amateur network. There were some attempts to go to 2400bps, but by then 1200bps was completely entrenched as a standard. This standard helped the Amateur packet network grow to huge numbers(at least at that time). By 1991, landline modem speeds had reached 9600bps, which was reckoned to be the maximum possible landline analog modem speed. The Internet and TCP/IP were starting to boom, and it was obvious that the Amateur community was going to have to do something; 1200bps was too slow to run TCP/IP(although it was great for learning the TCP/IP protocols, as you could actually watch the handshaking proceed!). Knowing that cheapskate hams wouldn't want to buy all new TNCs to run 9600bps, TAPR produced the $35 K9NG modem kit that could be interfaced to existing TNCs to upgrade them to 9600bps. Unfortunately, it was a piece of crap. They tried again a few years later, and actually produced a decent $70 9600bps modem(I still have a working model I built from a kit in 1994). TAPR was poised to produce another miracle, but it wasn't to be.

During 1993-1995, attempts were made to educate hams on how to upgrade their stations for 9600bps operations. The problem was, 9600bps was not plug-and-play like 1200bps was. Mike Curtis(WD6EHR) attempted to educate hams on how to build up a working 9600bps station. He held weekly 9600 baud packet workshops for those of us lucky to live in the Southern California area, and he produced his now famous, and mildly amusing, 9600 Baud Packet Handbook.

9600 BAUD PACKET HANDBOOK by Mike Curtis(WD6EHR)

Some progress was made in building a 9600bps network, yet most hams had become "appliance operators" and were not capable nor interested in attempting such "dirty work". The major radio manufacturers didn't help matters, either. They were slow to work on 9600bps-capable radios, and when they did produce so-called 9600bps-capable radios, they didn't work very good.

Then, in 1995, the Amateur Packet Radio Network market crashed, It was as bad as the Video Arcade Game Industry crash of 1981.

While the Amateur community was floundering with 1200bps technology, and attempting to educate users on how and why they should upgrade their systems to 9600bps, sophisticated algorithms and processors had pushed the landline speed limit to 28.8Kbps. This, in coincidence with the development of the Web and the subsequent explosion of interest in the internet, spelled doom for the Amateur Packet Radio Network.

After the crash, hams began to regroup, and try to think of new approaches. The Amateur Position Reporting System(APRS) utilizes inexpensive GPS equipment to breath new life into the old 1200bps packet equipment that was left gathering dust after the crash. TAPR began work on a 900Mhz Frequency-Hopping Spread Spectrum(FHSS) Digital Radio. After years of development, it is evident that the FHSS radio is going down the path of TAPR's other infamous doomed radio project of the early 90's: The packetRadio. Worse still, many amateurs look to TAPR for guidance in high-speed wireless networking, and since they don't see any information coming from TAPR, they wrongly assume that high-speed networking is too difficult. With simple $120 wireless networking cards, who needs a FHSS radio that operates on a band where Amateurs are secondary users?

TAPR

GRAPES

The Georgia Radio Amateur Packet Enthusiasts Society (GRAPES) developed the WA4DSY 56Kbps modem that puts out a 28Mhz RF signal that can be transverted to one of the Amateur bands where transmitting a 56Kbps signal is legal(typically 1.25m).

WA4DSY technology has been around for a long time - why didn't the WA4DSY modem catch on? First; it isn't cheap - it costs about $600 to set up a station, back in 1994 it probably would have cost about $1000. Second; it was TOO fast when it was introduced - the typical cheapskate ham's 10Mhz PC/AT "turbo" clone couldn't handle it. Third; it requires a high-speed networking card - they aren't easy to acquire, and the software for them was not very advanced in 1994. Fourth; it requires work - The software is typically Linux-like "roll your own", and the hardware is not plug-and-play - a pesky problem for today's "appliance operators". Fifth; it wasn't invented by an ARRL or TAPR crony - therefore it got little publicity. Sixth; the technology has now been superceded by inexpensive modified Part 15 devices.

WA4DSY 56Kbps RF modem

Amateur Radio Service

The privileges conferred by acquiring the NoCode Technician Class Amateur Radio license will allow experimentation and operation of high-speed digital communications stations on all Amateur frequencies above 30Mhz. A Technician Class Amateur Radio Staion, like a Part 15 device station, can be connected to the Internet through a gateway station(preferably through a cable modem or DSL connection). But, unlike Part 15 devices, these stations can legally be networked over larger distances, due to more relaxed antenna and power restrictions. A Technician Class license is very easy to acquire. All that is required is taking a 35-question, multiple choice examination covering basic radio and electronics theory with a passing score of 70%, or higher. All of the possible questions and answers are available on-line. It is also possible to take practice tests on-line, to see how you are doing. Study materials are available for a cost from the ARRL, and others; but they are really unnecessary.

Amateur Exam Question/Answer Pools
Take a Pratice Amateur Radio License Examination

Technologies like the Internet, Cable Modems, DSL, and Cell Phones have reduced the importance of HF communications. It is now no big trick to communicate world-wide with anyone, anywhere, anytime. Also, with the advent of much more efficient digital communications techniques like PSK31, the old ham HF mainstay mode -- Morse Code -- has become an anachronism. Recent restructuring of the Amateur Radio Service licensing structure has lessened the importance of Morse Code. There are now only three license classes - Technician, General, and Extra; and the General and Extra Morse Code requirements have both been lowered to 5wpm. Only International treaty agreements, requiring the ability to do a minimum of 5wpm to get on HF, are stopping the complete elimination of all Morse Code requirements.

Communicator Class License Proposal - To help get more young people interested in Amateur Radio
No Code International

ARRL

The American Radio Relay League(ARRL) is the largest organization of Amateur operators. While their membership includes hams with a wide cross-section of interests, it does tend to reflect the interests of the veteran ham population. As such, they are more focused on HF digital communications than high-speed/UHF digital communications. For instance, the on-line ARRL band plan for the 70cm UHF band does not even mention any digital allocations.

ARRL

Other Links

My Personal Radio Services Page
PubCel Home Page
Oswald Rocks!
Phil Hendrie

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