Putting Channel 22"A" in the blank spot      


Back in the early 1970's, during those initial days of steady growth which preceded the mass media-driven explosion of users who would come to know CB radio as the latest social fad, there were already a growing number of people who were truly interested in wireless communications as a hobby.  While most were not formally educated, their "hunt and peck" style of experimentation often yielded interesting results. Naturally, these budding hobbyists were constantly looking for innovative ways to optimize their setups. That competitive spirit often drove these early tech pioneers to push the limits of their setups (and sometimes their finances) to get the most performance that they could for their discretionary dollars.  Also back then, as the channels started filling up, there were, predictably, those personality disputes which started cropping up between rival channel groups.  These clashes usually revolved around differences in opinions, bleed over, and a very obvious generation gap.  And while it was not yet rampant at that time, there was a growing dark element of society which derived pleasure from disrupting the communications of other people.  Finally, there was the phenomenon of "DX" talking, which required some sort of "edge" over the other guy if one wanted to be truly successful. The dynamics of these converging conditions were often responsible for fueling the desire to modify our equipment beyond what was considered "stock", or legal operation.  One of the more commonly sought "modifications" involved frequency expansion. This is the story of one such mod.

In this case, the expansion consisted of only one channel.  The channel which is the subject of this article, has the frequency of 27.235 Mhz.  Once, this frequency was part of a land-mobile business band allocation.  Because of the relative ease in finding it in a typical synthesized 23 channel CB radio, and due to its close proximity to channel 22 (both in frequency and on the channel dial), it was given the nickname of "Channel 22A". To our young, just starting out on CB minds, Channel 22"A" was an enigma, and it held a somewhat mystical allure.  Having access to this channel was like membership in a secret club, and only the "top dogs" of the local groups seemed to have it.  It was also a bit of a status symbol, a cut above the general pack, if you could move to a "private" channel which the "common" people didn't have access too.  In the beginning, when we didn't even have all 23 channels yet, the appeal of "22A" was not fully appreciated. But once our teenaged group of locals managed to join the ranks of fully capable 23 channel rigs, it didn't take long before the desire to gain access to the mysterious "22A" started to occupy our time.  On a typical, modern out of box radio, the channel was defeated and the radio neither transmitted or received in the blank spot.  So as someone who was driven to learn all that I could about radio, I took it upon myself to find the solution to this obstacle.

For a little background (and every good story has some) on why this channel was there, and then deliberately defeated, we take a look back to those pioneering days.  Back then, while there were many different models of CB radio which had 3, 6, 8, or 12 channels, most high performance CB'ers ran full 23 channel synthesized radios which used quartz crystals as the frequency determining element.  Normally, a simple transceiver (And most radios with less than the full 23 channel compliment) required one crystal for the transmit frequency, and a different one (offset by the I.F frequency which was usually 455 Khz) for the receive frequency. When you increase capacity to the full 23 channels, that can add up to a bunch of crystals (46) under this scheme.  While this was certainly doable, crystals are not cheap and represented a fair percentage of the cost of an already expensive radio set in those days.  Engineers came up with a clever way to reduce the amount of crystals required, while still allowing full 23 channel capability.  What they came up with relies on the principle of frequency mixing.  If you take 2 different frequencies and combine them together in a mixer circuit, you will get, at the mixer output, frequencies that have both sum and difference components of the original frequencies.  With the proper filtering, you can then select which mixer products you want and reject the others.  The bottom line is that you can now generate many different channels, by mixing the same set of crystals in different ways.  Call it "crystal multitasking", to put it into 21st century terminology,  but the end result is that you can now generate the 23 channels from as few as 12 crystals.  Needless to say, this represented a significant reduction in the number crystals required, which directly translated into a cost savings.

So ok, where am I going with all this boring "technobabble"? Don't worry, I'm getting there...  So where were we anyway?  Oh yea, the most common method of generating the 23 channels consisted of a main set of 6 crystals, which were then mixed with another set of 4 crystals, to derive the main synthesizer output. That output was further mixed with a fixed receiver offset local oscillator, and a transmit mixer crystal.  Each crystal from the bank of 4 was mixed once with each of the crystals in the bank of 6. If you then use simple multiplication, you can see that 6*4=24, and that 24 is the total amount of potential channel combinations that can be generated with the installed crystals.  But wait a second! There's only 23 channels labeled on the dial, so where did that extra channel go?  Where indeed...... If you look at a typical 23 channel radio, you will see that the channel selector itself is 24 position but that most have a dial which has an extra "blank" spot, usually located between channels 22 and 23 (Hmmmm...).  Curious people wondered why the dial was set up that way.  Well, the straight up, no nonsense answer is that there is an extra, hidden channel there, the 24th channel which was created by the crystal synthesizer.  It so happens that this "hidden channel" has a frequency of 27.235 Mhz (Which is now Channel 24).  Very early, first generation synthesized radios actually had the extra channel enabled (but not labeled), but included strict instructions not to use the channel as it was not authorized for the class "D" CB service. The FCC wasn't comfortable with this "honor system" method of self regulation restricting access to an "illegal" channel, so they insisted that more effective methods be employed by manufacturers to prevent either inadvertent or deliberate use of this channel.  Sometimes the manufacturers put an accessory feature in the blank spot, like a P.A. function.  Usually though, that open spot was simply left conspicuously blank, but the radio would neither transmit nor receive there.  While not a legally authorized CB channel, it was nonetheless situated 10 Khz above Channel 22, and 20 Khz below Channel 23, which led to it being given the nickname of "Channel 22A".  But since mathematics cannot make 6*4=23, the FCC would have to rely on CB radio manufacturers to make this extra channel unavailable to the user.  But those efforts didn't stop people from attempting to exploit the truth in mathematics to their advantage when seeking to access this "bonus" channel.  

Manufacturers were given a fairly broad liberty in accomplishing the goal of removing "Channel 22A" from the hands of the general public. Most "defeated" the channel mechanically on the channel selector switch itself. The simplest form was a single tab on the switch gang which shorted one of the crystals out when in the blank position. This simple defeat was not always 100% effective and some radios equipped with this type of defeat mechanism could be "fudged" to work on "22A" by carefully wiggling the channel selector between the detents of either Channel 22 or 23 and the blank spot. If the selector had any "play" in it, you could usually successfully access the channel.  It required a steady hand and some patience to master, but in many cases you might be able to access the channel without having to open the radio's case at all.  Some radios though, utilized more complex defeats.  In these cases, each crystal "bank" would have a different wafer section of the channel selector.  Sometimes there would be a small gap in the switch plate on each section corresponding to the "blank" spot, which made the "wiggle" method nearly impossible to facilitate.

Those of us who lacked the patience to "wiggle" in the channel, or who otherwise wanted Channel 22A to be just as easy to access as any of the other 23 channels, usually resorted to circumventing the factory defeat mechanism's.  On some radios (like my Pace 223, Tram XL5, and Midland 13-885) the defeat mechanism could be disabled by a simple clip of a single wire (or two).  Other radios employed gaps in the channel selector,  which opened up the switch contacts when the "blank" spot was accessed.  This required a different and slightly more difficult method to reach the desired goal. I used to carefully solder a thin piece of copper ribbon across the gap, effectively removing it and restoring connectivity to the switch. This mod required some skill and a steady hand so as to not cause damage to the switch fingers.  Another, slightly less risky, method was to bend the main switch finger, on each wafer with a gap, slightly so that it would still be in contact with the switch plate while in the blank spot detent. The drawback to this method was that if you bent the contact too far, you could cause intermittent operation on either Channel 22 or 23 if you were not careful.  Still another method was to add an additional switch finger out of a stiff wire or from the pieces of a cannibalized channel selector from a parts radio.  Regardless of which methods had to be employed, the end result would be that you now had a 24 channel radio.  In the grand scheme of things, this may not sound like a big benefit for the effort required. But when placed in the context of the atmosphere of the time period, anything that you had, which your rivals did not have, was something to be proud of.

Adding this extra channel became a much sought after modification in those days and I lost count of the number of radios which I performed the mod on.  But in a way, by granting access to the channel to more people, I was destroying its appeal as an "exclusive" channel. This was yet another example of how capitalist greed trumps the desire for exclusivity....

When Phase Lock Loop (PLL) radios first hit the scene in late 1975, they added another interesting wrinkle to the mysterious allure of "extra" channels.  Radios like the Hy-Gain 623 placed a mechanical switch stop in the channel selector, which prevented the dial from completely rotating. They also placed the blank spot between channel 23 and 1, and by virtue of the switch stop, physically prevented the dial from selecting that spot. When the mechanical stop was removed, (A feat best performed by a heavy set of pliers) there was indeed a channel there, but it wasn't "22A". In fact the extra channel turned out to be Channel "19A" (27.195 Mhz, a class "C" radio control channel between channels 19 and 20). The Realistic TRC-152, also had a blank spot between 22 and 23 like a typical crystal controlled radio.  But when the pink defeat wire was cut, the extra channel which appeared there was yet another class "C" radio control channel ("15A", 27.145 Mhz). It was also discovered on early Cybernet chassis (Some Midland, Lafayette, G.E., Kraco, Hy-Gain and others) 23 channel PLL radios, that by utilizing the old faithful wiggle technique in between various standard channels on the dial,  several extra channels could be discovered. These initial examples gave us a small glimpse into the wonders of PLL radios and their frequency expansion capability.  But that's another story.........