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#13
January 14th 07, 10:35 PM
posted to rec.radio.amateur.policy
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One way to promote learning of code ...
wrote in message
oups.com... From: (Michael Black) on Sun, Jan 14 2007 12:24 am This is precisely why two-tone oscillators are needed for testing SSB transmitters. Because only then are you actually modulating the output. Otherwise, it's just a carrier. What happens at AF to RF translation in THIS group is the emotional-baggage tie-in to the mythos of morse such that direct RF on-off keying is somehow a "pure way" to send "CW." You may modulate the carrier with a tone but then it is not actually "CW" anymore. You may not think definitions are not important or consider those who wish to adhere to important definitions to be carrying emotional baggage, but definitions do have value and can be essential. Remember the story of the 1800's era Indiana state legislure passing a law to refine pie by rounding it off from 3.1415 to 3? Those lost in the mythos will contentiously state that audio tone generation (with on-off keying of the audio) translated to RF is "false" or "artificial." Without on/off keying of the RF, it is simply is not "CW". I give you this; you could call audio code that generates 2 RF states such as mark/space to be "CW's" (continuous waveS). When the frequency or phase changes to a different value from the original value, the "wave" ceases to be continuous. However, you could conceive of the two RF states as being 2 continuous waves that are either present or not, similar to 2 A1A transmissions (where one continuous wave is present or not). They are not equivalent. Not the same as A1A Morse. I do not consider belief in fact to be emotional baggage. Those folks just haven't made the connection to spectral content of ANY modulated signal...a few even contend that "CW" (on-off keying) "has no sidebands" because "it is just turned on or off!" :-) Actually. I have never heard anybody say that. I have heard your Canadian compatriot talk about transmitting "pure" sine waves which almost imples no sidebands, when not considering on/off rise and fall times when the RF is keyed (which he seems to ignore when he say says "pure sine waves"). Perhaps worse is the group that believes all-Class-C transmitters are "pure" in their spectral content (as if those had no harmonics)! Sigh... :-( Again, most people who talk about "Class C" amplifiers are familiar with their bias points being set above cut-off value for increased efficiency, therefore they have distorted outputs and such people would know know that they therefore generate lots of harmomics (and in some cases are intended to, as in the case of frequency markers). Those who are not aware of this do not tend not to speak about "Class C" amplifiers, specifically. They just talk about their "linear AMPS" (which are hopefully biased at more like AB than C :-)) |
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