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Fire communications is Jack, known as freecell, I have not heard much of him in a very long time.
Firebreather is Chris.
He and John at Panther electronics did a lot of playing with the RCI radios.
John was a awesome radio tech, one of the best in the country back in the late 90`s
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
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.
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.
I have no idea. but it scans like a good read in any case.
thanks for the post.
you wouldn't happen to have an antenna article discussing the differences between top, center, and base loaded would you?
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