Hi Don; Thanks for your input. A discussion of bandwidth is meaningless unless you tie it to how far down from peak voltage. The standard is 1/2 voltage or -6 dB down. However, as I remember, the 9 kc the FCC is talking about is further down. -26 dB if I remember right. We cannot compare apples to oranges. That may be 6 kc at -6 dB. The Canadian regulation is probably at the standard -6 db. So they may be the same. I think the implication is 6 kc @ -6 db and I am going to comply with that.
73, Ed Richards K6UUZ On Sun, 26 Sep 2004 18:02:32 +0000 "Donald Chester" <[EMAIL PROTECTED]> writes: > > >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 > > > ______________________________________________________________ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:[email protected] >
