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Summer 2003 Issue |
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OP ED Alternative Options for Resolving HSMM Interference Issues By John Champa, K8OCL |
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On the left is
the Logitech USB 1.1 Notebook Pro camera and its carrying case (for
information see <http://www.logitech.com>.
The large golf-ball camera on the right is the Orange Micro iBOT2, a USB
2.0 version of Logitech’s iBOT firewire camera (for details see |
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Many newspapers around the U.S. print a page entitled “Op-Ed.” This usually runs opposite the editorial page; hence its name. Sometimes the name takes on a double meaning, when the author has a viewpoint opposite to the editor’s. Its purpose is to give a writer an opportunity to express a view or propose an idea for discussion in a longer format than what is normally found in a letter to the editor. There are many views and ideas floating around in the world of VHF that are worth considering and discussing. Please note that the views expressed herein are those of the author and do not reflect the views of CQ VHF or its editorial staff. —N6CL Writing for myself, and not the ARRL High Speed Multimedia (HSMM) Working Group, I wish to respond to “Op Ed” in the Spring 2003 issue of CQ VHF regarding the 2.4-GHz band and the negative slant the piece gave to amateur radio spread-spectrum experiments on that band. One of the flaws in the spring “Op Ed” was the author’s omission of the fact that in the U.S. the unlicensed FCC Part 15 IEEE 802.11b devices have access to channel 1 through channel 11. However, the U.S. amateur radio 2.4-GHz band shares only channels 1 through 6 of that Part 15 service. Therefore, any Part 15 wireless local area network, or WLAN, station experiencing interference from an amateur station of any type needs merely to change its operating channel to one of those outside the amateur band. On the other hand, it must be noted that FCC regulations clearly require that any Part 15 user who is causing harmful interference to an amateur station must either cease operations, or correct the interference problem no matter how prestigious or wealthy the manufacturer of his or her equipment might be. That is the law. Recently, current FCC rulings confirmed this requirement when two unlicensed Part 15 cordless-phone-device, not WLAN, users were directed by the FCC to either cease operating or eliminate the sources of the interference to a licensed amateur radio station using the AMSAT-OSCAR 40 satellite downlink. At last report, the unlicensed Part 15 equipment owners had a friendly relationship with the amateur radio operator, and the Part 15 owners were working with the equipment manufacturer to correct the interference problem. Again, that is the law and that is the way it is being enforced. In like manner, any unlicensed WLAN Part 15 station experiencing interference from a licensed amateur high-speed multi-media (HSMM) station must accept such interference. It should be pointed out, however, that to date there has not been a single such report, so let’s get real. Even if every active amateur radio station in the U.S. were equipped with HSMM, it is doubtful there are sufficient numbers of us licensed amateurs to cause any problem for the millions of Part 15 WLAN users. Probably the most obvious reason for this lack of QRM is that the vast majority (but not all) of the unlicensed Part 15 users, both commercial and home-office WLAN, are located indoors and are using low, vertically polarized rubber-duck antennas. On the other hand, all amateur HSMM station antennas are outdoors and most use horizontally polarized, usually highly directional antennas up relatively high. These are much different RF environments.
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