Re: [Flexradio] Two (minor) suggestions on Operating Manual v 1.4

[Craig Monsen]

Joe,   I think that I have had a similar experience with the AGC oscillating at high max AGC settings. I thought that it had to do with the "crud" at around 0 Hz (-11.025 KHz) (ground loops, etc), overloading the sound card causing this oscillation. I have been trying to isolate and reduce this noise at the far left end of the panadapter with less than optimal success. Turning the max AGC setting down clearly reduces this oscillation. However, the sound level is concomitantly reduced, which is not desirable for weak signal copy.   I continue on my quest to reduce this "crud".   73 Craig KC2LFI ----- Original Message ----- From: Joe - AB1DO To: FlexRadio@flex-radio.biz Sent: Friday, August 26, 2005 2:32 PM Subject: [Flexradio] Two (minor) suggestions on Operating Manual v 1.4 Hi all,   I have the following suggestions regarding the operating manual:   1. In the discussion on windowing functions, the manual mentions that Blackman-Harris is  the "best" selection (page 88, heading Window). On page 90 a discription follows of Blackman, Blackman-Harris and Blackman-Nuttall. However, on the Setup/DSP/Options tab the Window selection shows Blackman2, Blackman3 and Blackman4. It is unclear to me which is which. A link in the manual from one to the other would be desirable, but better perhaps changing the terminology on the Setup/DSP/Options tab to match the more descriptive ones of the manual.   2. Regarding the AGC settings on Setup/DSP/Options the default Max Gain is 68dB. However, on my system, I noticed that at this threshold setting my AGC was unstable and oscillating, resulting in an audible "pumping" of the audio volume with just band noise present (-130dBm). I finally figured out what was going on (thanks to the recent outstanding paper on AGC by Phil VK6APH). Lowering the gain to 50dB resolved the oscillating. No mention of possible oscillation is mentioned on page 87 of the manual. Although I understand that the AGC is being looked at, a warning of the possibility of AGC oscillation at too high a setting of Max Gain is perhaps a good idea (we are not all blessed with Phil's intricate knowledge of AGC systems). Prudent might also be a slightly lower default setting of Max Gain, but I guess that would depend on how unique AGC oscillation at a threshold of 68dB is.     73 de Joe, AB1DO _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz