License-Free Spread Spectrum Packet Radio
By: Albert G. Broscius, N3FCT 1989
Implications for the Radio Amateur
While it may be disheartening that commercial systems have become available before their amateur counterparts, it should be mentioned that these license-free systems may be used to augment or supplement our communications abilities even though they are not regulated under Part 97 of the Rules. It is also possible that a system which qualifies under 15.126 could be modified to be pursuant to Part 97 spread spectrum rules and thus allowed to operate at the higher power limit, one hundred watts, available for amateur spread spectrum as long as the control operator satisfied all appropriate requirements of the Rules. And of course, placing a 15.126 unit on a Microsat-class vehicle could pave the way for license-free space operation although there may be other restrictions which come into play in that situation.
The design of a power-limited spread spectrum network with realistic inter-node distances would require substantial antenna engineering skills which could be provided by amateur operators familiar with propagation conditions on these bands. However, the resulting network would be free of Part 97 restrictions in the spirit of the pre-Commission Ham activities. Realistically, a Wild West scenario of competing BBS networks and CB-style chaos could make this non-Ham world an unpleasant environment. Unfortunately, unless a pro-active position on this technology is taken, we may see a digital CB world forming around our shared allocations.
Neglecting intentional interference to amateur transmissions and power-limit abuses, there is still the issue of a high noise floor on the weak signal portions of the shared bands. Although these bands now suffer from their shared status, some fell that an influx of consumer electronics items which may each transmit up to one watt will cause unacceptable degradation on the "quite regions" of the band plan. Considering the possible density to be tens of radiators per city block, the argument of RF pollution seems credible.
To responsibly address this technology, we fell amateur operators should experiment with the commercial systems now available in establishing long distance communications paths using high-gain antenna systems coupled with the maximum legal power of one watt, determining interference levels seen by week signal receivers attributable to spread spectrum transmissions, and carefully introducing this technology to computer bulletin board operators who could financially support development of an unlicensed computer internet.