On 12/16/2012 7:40 PM, W2RU - Bud Hippisley wrote: > Admittedly, it was stupid to open an ionospheric-skip band to a supposedly line-of-sight service,
The CB Radio Service was created when the 11-meter band was reallocated internationally to "Industrial, Scientific, and Medical" services (ISM) - in essence, an electronic garbage can used by diathermy machines, industrial heat sealers, and similar non-communications radiators. As such, the FCC felt that if the new users can make communications in that mess, it's all theirs. The first CB users were rather law-abiding -- that went downhill in the mid-1960s. During the 1960s it was very common to hear such signals sweeping through the band. The main reason that we don't hear them today is that they were usually using unfiltered DC, and rich in harmonics. The third harmonic fell in the aviation bands, and caused harmful interference. The FCC had a very extensive effort to close down such devices - in fact, they were the only devices that an FCC enforcement agent could order closed down on the spot with no notice or hearing. The sweep was due to heat sealers (think waterbed mattresses) changing frequency as the material - the dielectric in a capacitor so to speak - changing as it heated up. Those devices were required to be used in shielded rooms or at other frequencies, usually the ISM microwave bands. So much for that history lesson - "I was there". 73 de K2ASP - Phil Kane Elecraft K2/100 s/n 5402 >From a Clearing in the Silicon Forest Beaverton (Washington County) Oregon ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
