Sounds like a SDR could possibly automatically compute a best AGC-T setting by looking at an average of the 1% lowest signal content frequency bins across the band.
- Dan, N7VE -----Original Message----- From: flexradio-boun...@flex-radio.biz [mailto:flexradio-boun...@flex-radio.biz] On Behalf Of Lee A Crocker Sent: Monday, June 29, 2009 10:00 AM To: Flexradio Subject: Re: [Flexradio] Automatic Gain Control Threshold "AGC-T" versusreality The AGC threshold is basically the threshold where the AGC starts to reduce gain. That threshold is in no way set and forget. It is based on the band noise, and it should be set for each band/antenna combination. What AGC does is reduce gain. If you are trying to hear a very weak station at the level of the noise the LAST thing you want is your gain to be reduced. Being able to control this level therefore can be the difference between copy and no copy. It also is what makes the receiver so quiet. If you set the AGC-T correctly you can hear every signal on the band but you are not attaked by the constant drone of noise. The way AGC-T is set is to find a clear place on the band and set the AGC-T to where the noise is barely perceptible. You may need to increase the value the Audio to compensate. This maneuver sets up gain distribution across the stages of the radio, and it is set up correctly and remembered for each band, and for each season. Summer time static in a properly set up F5K or F3K melts into the background, while in the winter when the static is gone you may well want to run the receiver in a different position because the noise is so much less. The point being if static is S-9 you are not going to hear anyone that is S-1. If noise is close to S-0 then a S-1 signal is Q5. Alternatively you would never want to run the radio set up for S-0 conditions with S-9 static. This is exactly why it is not set and forget and needs to be adjusted for each band according to the noise that exists on each band. Legacy radios are clueless when it comes to this understanding of how to distribute gain. They are clueless largely because their gains are set in stone and can not be adjusted, AND thier AGC loops are a hodgepodge of non linear gain and distortion. This is the exact reason most legacy radios are not linear across the S meter reading. What you see on the S meter is merely a error voltage that tells you how much AGC is being employed. The Flex gives you a linear response across the dynamic range, so in a properly adjusted Flex the radio hears super strong stations with the same ability as it does stations virtually under the noise. If you are not experiencing this then it is likely you have not set up the radio correctly. 73 W9OY _______________________________________________ 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.flex-radio.com/ Homepage: http://www.flex-radio.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.flex-radio.com/ Homepage: http://www.flex-radio.com/
