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Packet Radio
Good Stuff, Cheap

Francis Vale

 

A Ham By Any Other Name

Why wait for digital Personal Communications Services to come to your neighborhood, when you can roll your own PCS-style wireless system today? And moreover, not have to pay a dime in user access fees to Ma Bell?

If this novel idea grabs your interest, then you should know about packet radio. Packet radio is another mode of Amateur Radio, or 'Ham' radio. All those geeks who stayed up late at night with racks of short-wave radio gear to talk to their buddies around the world have now gone digital.

The Hams dumped their telephone computer modems in favor of terminal node controllers (TNC), and then neatly sidestepped Ma Bell by using all that freebie amateur radio bandwidth. Packet radio takes your computer data stream (which can be text, video, or audio), wraps it all up into short, small bursts, and merrily sends it along to another Ham buddy's similar equipped amateur radio station.

Shazam! Instant, no cost, all digital, PCS!

The Canadians were the first to seize upon this novel idea, and packet radio users in Montreal went on-line on May 31st, 1978. Some of their countrymen at the Vancouver Amateur Digital Communication Group (VADCG) then proceeded to develop the first TNC in 1980. At a 1981, Tucson IEEE meeting, a spirited discussion took place about how to make a low cost version of VADCG's TNC for radio amateurs. The Tucson Amateur Packet Radio Corporation (TAPR) thus came into being. Lyle Johnson and Den Connors, made the first TAPR-originated unit, called the TNC-1; and on June 26th, 1982, said their first digital hello. The TNC-2 quickly followed, and is now the de facto worldwide standard for packet radio.

Things have been rapidly progressing ever since. Today, you can buy a digital signaling processing-based packet radio system from TAPR/AMSAT (Amateur Satellite Corporation; of which, remarkably, they now have many orbiting about). The DSP-93 software can also support data, audio, and video. The two part unit has a DSP on one card, with the radio/computer interface board on the other. The DSP engine, a Texas Instruments 320C25, provides the computer horsepower.

For the DSP-93's $430 kit price (call TAPR to order, at 817-383-0000), you can now build your own fully programmable, very powerful, PCS-style system that easily interfaces to your Mac or PC. While you are on the phone, you might also want to spend $15 for an annual TAPR membership, and join the 3,000 others in the group. Low cost shareware for the DSP-93 helps to propel the amateur spirit along. For the less adventurous, there are several fully assembled variants of the DSP-93 also available.

TAPR's pioneering efforts share a strong family lineage with the history of the PC; the latter also having its roots in home built kits. Via CSMA/CD (Carrier Sense Multiple Access/Collision Detection, as used by ethernet) packet radio allows many simultaneous users on the same frequency channel. There are also personal BBS setups for leaving packet radio 'mail.'

Most amateurs use off the shelf VHF/UHF gear for packet radio transmission speeds of 1200 baud. But with special or modified VHF/UHF gear, and even microwave, transmission speeds quickly go up to 9,600 baud, and beyond. In terms of range, a lot depends upon power, surrounding hills, buildings, and other such obstructions, but at the 144-148MhZ packet radio bandwidth, the range can fall anywhere between 10 and 100 miles.

More than that, packet radio allows up to 100 watts of transmitting power, versus the measly 1 watt of PCS. Significantly, along with AX.25 ( X.25 modified for amateur radio), TCP/IP is also supported by packet radio. There are also a variety of methods to build low cost packet radio networks.

To Be an Unabashed Ham or Not?

But why would anyone want to use packet radio when full blown, commercial PCS wireless systems are on the way? Easy answer: packet radio's wide spread software support, and great user flexibility. Grab your PC, plug a DSP-93 into its serial port, add software, power, and antenna, and you are on the air. And not just with some limited functionality PCS data/phone, either. You now have a high powered, flexible, all digital, wireless computer communications system.

Implementing client server systems over PCS is surely on every one's wish list. But full fledged, data-centric PCS will be slow to come. Moreover, who will provide the software? Your PCS access provider? Do they know your business requirements? Quite frankly, until the requisite PCS/client server software development kits arrive, it is unlikely the PCS access vendors will be of much help to you.

But if your needs match up with the range limitations of packet radio, and your organization has the developer staff, then packet radio offers the opportunity to put in place, as of today, a TCP/IP-based, all digital, wireless, client server prototype system that can span a metropolitan-sized city area. And if you put the TCP/IP Web + 'Net computing model together with wireless packet radio, you just might have something really hot.

Packet Radio also offers software that supports GPS (Global Positioning Satellites), providing real time geo-tracking. Lastly, spread spectrum, frequency hopping techniques, like those used in commercial PCS, are also coming soon to packet radio.

Low cost and/or shareware for the DSP-93, plus a supportive user community also will help drive down the price of your wireless prototype implementation. And better yet, the whole setup costs nothing to run!

Amateur Radio, by law, prohibits its commercial use, but proof of concept prototyping/experimenting is usually OK. Although licensing may be required in some cases, anyone can license a commercial frequency to digital data.

If you really like your prototype, just buy your own VHF/UHF channel and commercialize your system (presuming you can get a license in your market). And for a commercial grade radio, you can buy, for a few hundred dollars, one of Motorola's advanced radio packet modems, such as the RPM4X5i, the highest performance radio currently available in the world. This DSP-based system is small enough to fit in your breast pocket.

This is one deal Ma Bell would rather you didn't know about, don't you think?

Copyright 1996, Francis Vale All Rights Reserved

21st, The VXM Network, http://www.vxm.com

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