What about bandwidth? +/- 5kc would be a 10 kc band width. I thought we were supposed to limit our band width to 6kc. Please correct me if I am wrong.
That is a popular urban myth. There is NOTHING in the US regulations that specifically limits bandwidth. The regulations specify "good engineering and amateur practice", and deliberately leaves the specific bandwidth vague. In Canada, there is a rule on the books limiting bandwidth to 6 kHz, but I have never heard of them enforcing it against AM signals that may exceed that figure. Besides, accurate measurement of bandwidth would require a visit to the station with test instruments. Over-the-air measurement leaves too many possibilities for error due to propagation, QRM, QSB, etc.
The US regulations could be interpreted to mean a reasonable bandwidth for the mode being used, considering band occupancy . If you had a cw signal with so much noise, hum or FM on the carrier that it was 3 kHz wide, the FCC probably could interpret that as a violation of good engineering practice. If the band is empty, as for example, 10 m. most of the time nowadays, or 160m in the middle of the day, you could run hi-fi AM with audio all the way up to 15 kHz and that would probably be ok as long as you made sure you were not causing any harmful interference to anyone. On the othre hand if you were limiting the audio response to 3000~ and generating the same wide bandwidth due to splatter (overmodulation or distortion), that would be considered not to be "good engineering practice." If you operated the full hi-fi audio at high power on 75m at night when the band was crowded, that could be interpreted as violation of good amateur practice.
The bottom line seems to be, use common sense and adjust bandwidth according to conditions, and make sure your transmitter's spurious distortion products fall within the FCC's specifications, which are listed in the rules.
There was a flare-up regarding bandwidth a year or so ago, with "hi-fi SSB". This resulted in petitions to specifically limit bandwidth. The FCC apparently turned them down. Now the ARRL is proposing to change the definitions of subbands to be defined by bandwidth instead of emission mode, to promote "digital" experimentation. The proposed bandwidth limit for AM is 9 khz. The League has received so much mail questioning the wisdom of such a change, that the League seems to be rethinking the idea. They still have an open invitiation to the amateur community to send them comments and opinions on this subject.
Don K4KYV
