Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!texbell!vector!telecom-gateway From: paul@devon.lns.pa.us (Paul Sutcliffe Jr.) Newsgroups: comp.dcom.telecom Subject: Re: SW or CB Mobil Radio: Legal? Message-ID: Date: 11 Sep 89 03:16:56 GMT Sender: news@vector.Dallas.TX.US Reply-To: "Paul Sutcliffe Jr." Organization: Devon Computer Services, Lancaster, PA Lines: 50 Approved: telecom-request@vector.dallas.tx.us X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@vector.dallas.tx.us X-TELECOM-Digest: volume 9, issue 364, message 4 of 5 In , Mark Smith wrote: +--------- | Actually, CB Radio, which doesn't require a license, is located | between 27 and 28 MHz. I don't know what the channels are exactly in | that range, but I do remember that they are not in a purely sequential | order, due to the expansion from 23 to 40 channels. +--------- I'm taxing my memory for this, so I may be giving invalid data, but anyway: The original 23 channels were .01mHz (10 Kc) apart, and ranged from 26.985mHz (channel 1) up, except there was .03mHz (two empty channels) between channels 22 and 23 (at 27.225, I believe). We CB'ers used to refer to them as 22A and 22B. Most 23 channel transceivers were crystal controlled -- there were a half-dozen-or-so crystals to make up the 'set'. Some more 'experienced' CB'ers would hook up a DPDT switch to get 22A and B. Later, channels 24 to 40 were assigned up through 27.405mHz. I seem to recall the old 22A & B frequencies being officially assigned as channels 24 and 25, but I'm not sure about that anymore. Then came PLL (phase lock loop) technology (along about the time of the 40 channel sets). The PLL circuit synthesized the 40 frequencies, but actually 'knew' a much broader set of frequencies. I remember having used my external speaker/PA switch to allow 'below channel 1' (under 26.985) and 'over 40' (27.415 through 27.805) dialable from the channel changer. - paul PS: disclaimer: I haven't touched my CB radio in at least 10 years. -- INTERNET: paul@devon.LNS.PA.US | How many whales do you have to UUCP: ...!rutgers!devon!paul | save to get a toaster? [Moderator's Note: Actually the first 23 channels were 26.965 through 27.255. They were 10 kc. apart, with '3-A' at 26.995; '7-A' at 27.045; '11-A' at 27.095; '15-A' at 27.145; '19-A' at 27.195; '22-A' at 27.235; '22-B' at 27.245 and 23 at 27.255. The so-called A and B channels were really not for CB use at all. They were garage door openers; radio controlled airplanes and similar. When CB was expanded to 40 channels, channel 24 and 25 were squeezed into 27.235 and 27.245 respectively, meaning 24 and 25 are actually 'lower' than 23. Channels 26 through 40 follow evenly upward 27.265 through 27.405. And yes, those PLL chips were really something, weren't they! With a little luck and a golden screwdriver, those guys could get the thing to oscillate all the way up to ten meters. But the feds started raising cain with Uniden and Motorola, among others, and forbade the further manufacture of the chips which could be programmed like that. Everything had to be done in ROM from that point (around 1980) onward. Are any CB radios still coming out with those programmable chips? Probably not. PT]