I gave up on am broadcast. There's too many stations on the same frequencies. All I hear at night is a cacophony of overlapping interference on every channel.
Sent from my iPhone On Dec 15, 2011, at 9:03 AM, "David R. Wilson" <da...@wwns.com> wrote: > For many years now on the short wave bands broadcast stations have been > using CCM (Controlled Carrier Modulation, also being called other names) > to reduce the carrier as much as 6db. That along with multipath can > cause some strange distortion problems on the receive end. That has as > of a few weeks ago been approved by the FCC for AM broadcast. Add to > that stations can do 125 (or more) positive peak modulation and it makes > clean decoding a bit more of a challenge. > > Dave > KU4B > > > On Thu, 2011-12-15 at 03:51 -0500, ke...@3950.net wrote: >> On 12/14/2011 10:47 PM, Brett Gazdzinski wrote: >> [...] >>> What as the problem with early versions of psdr and the agc working >>> off the audio? >> [...] >> >> >> >> For those who want the best fidelity from AM, the problem is this: >> The carrier gives an almost perfect reference for receiver AGC, >> without having to depend on the transmitted audio level for AGC >> detection as one necessarily does in suppressed carrier SSB. If you >> allow the audio level to be a factor in AM AGC detection, then you >> lose some of that fidelity (dynamic range preservation) advantage -- >> the AGC becomes a _de facto_ audio compressor, and those who care >> about fidelity cringe at that. They complained about it and got it >> changed. But people with less critical ears might never have noticed >> the problem. >> >> I do wonder if there is now clipping happening somewhere in the >> receiver / audio system since the change, when you're receiving one >> of those amateur AM stations that likes to run 150% or 200% positive >> peak modulation (AM broadcast stations usually limit themselves to >> 125% positive). >> >> If so, maybe the ability to switch in lower post-detector gain, or >> peak AGC, on such stations should be added. When extremely high AM >> positive peaks are present, a light could flash, too. It could be >> labeled "W3DUQ." >> >> >> 73, >> >> Kevin, WB4AIO. >> >> _______________________________________________ >> FlexRadio Systems Mailing List >> FlexRadio@flex-radio.biz >> http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz >> Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ >> Knowledge Base: http://kc.flexradio.com/ Homepage: http://www.flexradio.com/ > > > > _______________________________________________ > FlexRadio Systems Mailing List > FlexRadio@flex-radio.biz > http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz > Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ > Knowledge Base: http://kc.flexradio.com/ Homepage: http://www.flexradio.com/ _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flexradio.com/ Homepage: http://www.flexradio.com/
