Debunking AMC Modifications This article has been in the works for some time and has been painstakingly researched. The information contained herein applies to all operators of am transmitters. The all too rampant fad involving the destruction/alteration of this critical circuit is the subject of this editorial/article. Anyone tuning thru the Citizens Band and the so-called freeband allocations immediately above and below the 11 meter band must almost certainly agree that cleanliness of emissions and spectral purity / harmonic distortion products are clearly the furthest things from anyones mind. To start this off let's review a list of the "side effects" of this particular modification. Action: AMC Circuit Disabled Results: (What You Get) Excessive Levels of Interference to Commercial/Consumer Electronic Equipment / Yes Excessive Levels of Adjacent Channel/Frequency Interference/Splatter / Yes Excessive Levels of Harmonic Distortion Products / Yes Severe Clipping of Transmitted Signal/Waveform / Yes Excessive Levels of Heat in Related Circuitry / Yes Premature Destruction of Related Components / Yes Greatly Reduced Mean Time Before Failure / Yes Higher, Inaccurate Power Measurements / Yes Distorted Transmitter Audio / Yes Reduced Duty-Cycle Ratings / Yes Results: (What You Don't Get) Good Reputation / No Increased Tx Audio / No Increased Power Output / No Increased Operating Range / No Increased Signal Readability / No Gentlemanly Consideration From Others / No Some of us who are a little further ahead of the game than most realize that there are still a few options here for enhanced performance having nothing whatsoever to do with the AMC control circuitry. The Ham Radio Operators knew back in the 50's (as some of us now do) the only goal worthy of pursuit at this stage of the game is to determine how much power in the upper and lower sidebands of an am signal is too much. Any educated AM Operator realizes that a certain amount of carrier must be present so that the listening receivers detector circuitry can properly demodulate the signal and provide something resembling a human voice to the receivers audio output/speaker. This process with which the hams were experimenting was referred to as SuperModulation. In stark contrast to the current "Good To The Last Drop" mentality prevailing in most of the above-mentioned spectrum today the hams realized that this process could be achieved in tube-type equipment without sacrificing purity of emissions, etc.. The trick was to determine, with a given amount of carrier, how much power could be developed in the upper and lower sidebands of an AM signal before it was "too much". Generally speaking, it was found that when the total power contained in both the sidebands of an AM signal/carrier combined approached a ratio of approximately 4:1 with respect to a given level of unmodulated carrier that optimum results were obtainable without unduly sacrificing spectral purity. Yaesu pretty much proved that out. By comparison, AM broadcast stations, in an effort to maintain spectral purity at extremely high power levels are held to a figure/ratio of approximately 1.5:1. That is, modulated power output from the station is + or - one and one half times the unmodulated carrier level. All other things being equal, the best sounding AM transmitters will be operating within these parameters. (from 1.5:1 - 5:1) With regard to the 5:1 figure, this is again pushing the envelope. Purity of emissions begin to suffer typically from this point on. Although most of my operation involves ssb, it is rather disheartening to talk with operators in other parts of the world only to find out that they consider CB AM/SSB Operators in this country some of the most inconsiderate with respect to the trashy sounding transmitters in use. They are absolutely right too. In Australia, the equivalent of our FCC is the ACA. Most operators that I have spoken with tell me that there have been no "busts" for ten years or better down under, simply for two reasons. First of all, they police their own. Instead of merely "putting up with lid operators and trashy sounding, modified equipment", they instead make every attempt to educate the newbies and thereby reap the benefits of being "left alone" by the ACA. They also don't have thousands of retail CB Chop Shops filling them with hype and misinformation in an attempt to "give them the business" either. Consider also the fact that our Aussie friends pay 3 - 4 times what we pay for the same equipment and you begin to understand that these guys don't have the time or the money to offer up their new gear as guinea pigs for sacrifice on the local hacks bench. Unfortunately for CB Radio as a whole, the advent of the internet has only made it possible to disseminate more hype and misinformation at a faster, more voluminous rate. Well written college texts or technical books on the subject remain the best source for reliable information, as well as a small handful (relatively speaking) of internet sites. This site/shop will continue to stand in the minority where it has been all along and continue to expose the ongoing, blatant attempt by the majority of radio related web sites/shops dealing with this subject for the money-grabbing, technically challenged and deceptive extortionists that they are. Why should you have to be continually replacing your equipment instead of enjoying years of trouble-free service from the rig that you have now? I have heard some refer to this process as "upgrading". More like replacing the rig that just quit working or "burned down" after a year or two. (and these are the lucky ones) Upgrading would be leaving behind that AM technology which is 60 years out of date and picking up a new rig with ssb capabilities The market has fed you the bull and turned an otherwise durable, long lasting piece of equipment into another throw-away disposable commodity in an effort to keep the product flying off of store shelves. And you not only bought into it, you helped. Quit believing all of the hype and talk about "modifications". Unless of course you have a piece of equipment that has been working flawlessly for 25 years or so. Since the Mean Time Before Failure for most of the components in this stuff is about a hundred years or so this shouldn't be too difficult to achieve. Or is it? E-Mail me and let me know about your own similar experiences. Disable the AMC? The only one that loses is you........ ........all the way around.