Art Goddard suggested I share with you the following exchange that he and I had a few months ago. Dave K1ZZ -----Original Message----- From: Art Goddard [mailto:w6xd@attbi.com] Sent: Thursday, May 02, 2002 3:01 PM To: David Sumner K1ZZ Cc: Jim Haynie W5JBP Subject: Is there a Limit? Hi Dave- At Visalia, a couple of members expressed concern to me about the SSB "Hi-Fi" operation on 14.178, and other frequencies. According to these members, the Hi-Fi proponents have modified their radios for up to 6KHz of audio bandwidth and are unnecessarily disrupting nearby operators. 97.307(a) says use no more bandwidth than necessary. ITT's Reference Data for Radio Engineers states that 3KHz is the necessary audio bandwidth for communications-quality radiotelephone and 4-10KHz for sound broadcasting, "depending on the quality desired". Since broadcasting is prohibited (97.113) what is the justification for broadcast audio in the Amateur Radio Service? Is there any limit? Is SSB with 6KHz bandwidth (J6E) OK? The ARRL FCC Rule Book, 12th ed., p 4-27, appears to side with the HI-Fi folks, bounded only by "good amateur practice". If J6E is OK for SSB radiotelephone, then 6KHz is OK for SSTV and any other non-phone emission (97.307(f)(2)). And if 6KHz is OK for SSB, then 12 KHz is OK for AM. May QST, p13, carries an ad for Ten-Tec's Jupiter radio heralding "Great Audio!" with built-in DSP selection of transmitted audio up to 3.9KHz to "deliver the finest sounding audio in amateur radio". By carrying this ad, we have aligned ourselves with the Hi-Fi proponents, at least in some people's eyes. "It Seems to Us" there's an opportunity for ARRL to provide some guidance here... 73, Art -----Original Message----- From: Sumner, Dave, K1ZZ Sent: Friday, May 03, 2002 4:11 PM To: 'Art Goddard' Cc: Jim Haynie W5JBP Subject: RE: Is there a Limit? Hi Art, Occupied bandwidth is defined as 26 dB down from mean power. The bandwidth of a voice signal is heavily dependent upon the individual voice characteristics. Even if a transmitter is deliberately designed to pass voice frequencies above 3 kHz, it will be a rare voice that contains much energy at those frequencies. Looking at it another way, is there an affirmative obligation on an amateur to filter out of his or her transmitted voice signal, frequency components that are present in his or her voice? I don't believe there is. Poor IMD characteristics and excessive power are more likely to cause problems than broad transmitter filters, it seems to me. But I admit that I seldom listen with a filter wider than 500 Hz. 73, Dave K1ZZ