We on this reflector have often "beat to death" the American FCC Amateur service rules about bandwidth since they give no numbers about what is acceptable as long as the emission stays within the Amateur band. Unlike commercial frequencies, where specific technical standards avoid co-channel interference with other services, the rules for Amateur emissions are vague in keeping with the basic philosophy about not having rules where no rules are required.
>From a technical standpoint, the signal-to-noise ratio drops as the bandwidth increases. The best signal to noise ratio for a given effective radiated power is found at the narrowest bandwidths. That's why CW works with signals that can't be heard at all on SSB, and why SSB gets clear copy with signals unreadable on AM. Even if the receiver filter is tailored to match the signal, the amount of noise power increases in direct proportion to the bandwidth. The effect upon the listener is that the noise gets louder and the signal weaker as the bandwidth is increased. So, without trying to argue the law, that is a solid technical reason to maintain narrower bandwidths whenever possible. In free society, such as the USA, begins with the concept that citizens can do *anything* that pleases them but, to avoid injury to others, we must adopt laws prohibiting specific behavior. The objective is to have as few laws as possible, and to write the laws to prohibit exactly the behavior that is damaging. Of course we Yanks didn't invent the concept. One predecessor was the Magna Carta. Sure, some Americans don't understand that or they choose to "freeload", taking advantage of anything they can get away with without respect to the law. That injures the rest of us, then we're further put out by having to pay to keep them locked up when they are caught. But the vast majority of Americans I've known over my lifetime are what we call "honest, law-abiding citizens", in spite of what the movies suggest. Indeed, like all good story tellers, novels and movies dwell on the unexpected and unusual, not the commonplace. Ron AC7AC -----Original Message----- Of course, the FM filter can be used for AM transmit. All you need to do is tell the radio it is an AM filter. It will not know otherwise. There is really no reason not to transmit wide band AM, just like there is no reason not to transmit wideband SSB. The modes are perfectly legal in most of the world. For voice, it is a waste of spectrum but for digital modes, especially on the higher bands having more audio bandwidth may be useful. I think it might be that, in the USA it is not legal to transmit 15kHz wide AM or SSB. This is a difference between the USA rules and the rules elsewhere. In the USA, people are expected to do foolish things unless they are told not to, hence the limitations on transmitting out of band. Here in Europe, we have just as many fools, but it is considered their responsibility. We suffer greatly because of this but it also gives us a lot of freedom. _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
