Hi Sonwatcher,
I would figure Inspector Morse might know this one, but I'll pass on what I remember from the bad old days of 1977.
When the FCC pulls certification of equipment, they will announce "sunset" dates, after which they may no longer be sold, and later on, used.
I'm probably wrong about the exact intervals, but seems to me that a 23-channel radio was no longer legal to sell as of 1982 (five years). The "not legal to use" date was a year or more after that, I think? Or maybe it was the same year? Not sure how many tons of old magazines I'd have to look underneath to find the original info.
The FCC would make a habit of "phasing out" old technology in stages, to ease the financial burden on users. Did this with the old "wide-band" FM-business 2-way radios 40 years ago. Folks who had a license for an old "wideband" 2-way system were given a few years to upgrade their FM 2-way stuff to "narrow band". New licenses were only granted for narrow-band equipment. When the last "wide-band" license expired, the industry had been upgraded. Likewise when the 2 MHz AM marine radios were phased out, it was announced five years in advance, giving everybody time to upgrade to VHF-FM marine radios.
The only "strictly legal" way to sell a 23-channel CB is to "disable" it. A working 23-channel CB is NOT legal to sell, OR to use. Honest.
There really was a point to this. The technical "hoops" that a 23-channel radio had to jump through to get "Type Acceptance" were pretty wide. No limits on many kinds of unwanted output from the transmitter. No limits on what could leak out of the receiver. A really loose set of standards, all in all.
When the FCC got talked into adding frequencies, they also addressed the technical-performance shorcomings of CB radios, with an eye towards interference problems. The proliferation of CB during the mid-70s was putting a lot of heat on the FCC from interference complaints.
When government agencies write new rules, they are always late to communicate them to the public. You know, the folks who are obligated to obey them. Late in the game, long after announcing the 17 new channels, the FCC got around to publishing the new technical requirements a 40-channel CB would have to meet to get "Certificated" as a legal-to-sell (and use) CB radio.
Manufacturers were desparate to sell ANYTHING during this "limbo" period. The explosive growth of CB had led them to sink every penny they had into producing product. The entire product pipeline, from the factories, in warehouses and on retail shelves became worthless, overnight. Nobody would buy a 23-channel radio when the "forties" were just around the corner. This led to creative marketing promises like "we'll put a 40-channel selector in it for free (later), just buy it now". Or, they would promise to exchange it for a 40-channel model, plus a small fee when those radios became available. JUST BUY ONE NOW! PLEASE, PLEASE !! Was the gist of all this.
Having all their assets made worthless overnight bankrupted 98 percent of the folks who made their names in 23-channel products. This made some of those "upgrade" promises moot all by itself. But when the FCC released the new technical performance specs for a 40-channel CB, there were lots of new restrictions. To make a long story short, this dictated a lot of added components, to filter every socket on the radio. Filters on the mike socket, PA, external speaker and power cable were never needed for a 23-channel CB. Without those, a radio would have too much stray RF leaking out of it and would flunk the 40-channel lab-measurement limits. Upshot was, that the "channel-selector upgrade" promise was ALSO moot, and led to "exchange credit" offers, replacing the "we'll upgrade it" promise.
The real injury came when the first 40-channel radios finally made it onto retail shelves. In the meantime, the price of a 23-channel radio finally fell to where you could sell one. They were being sold by the pallet for nothing at bankruptcy auctions all around the country. This made the price you could get for a 40-channel too low to make a profit. More folks went bust when they overestimated how many 'forties' they could sell, and how fast, and for how much.
Hmmm. Can't remember if the "sell a '23' new" cutoff date was one year or two? Pretty sure the "can't sell used or transmit" date was 5 years. Would have been 1982, maybe 1983? I was lucky. Sold all the 23s I had without going bust. Lost money on them, though. I've slept since those days. Just don't remember, exactly.
In a nutshell, the FCC considered the 23-channel equipment technically inferior to a radio that met the new 40-channel requirements. That's the reason their use was eventually banned.
One amusing side note to all this. The tendency of a radio's mike cord to soak up transmitter RF, causing feedback howl was a LOT worse on many 23-channel radios. The same filtering that keeps stuff from leaking OUT of a radio also prevents it from leaking IN FROM YOUR LINEAR.
On the whole, a 40-channel radio will behave a lot better around a 'dirty' linear than a 23-channel radio. FAR less likely to squeal with the mike gain turned up. Not what they intended, but so what? The whole experience was a lesson in "Be careful what you wish for, you might just get it". Always wondered how many folks who lobbied for more channels went belly-up BECAUSE their "wish was granted".
73