Re: [Flexradio] Need AVC
If you don't mind a little complication you can get what you want from a voltage controlled amplifier, typically an audio amplifier IC whose volume is controlled by a DC voltage. You rectify a sample of your audio, scale it with a pot and apply it to control the gain. Depending on the component selected you may need to invert the sense of the control voltage. Alternatively you can buy a COTS (Commercial off the Shelf) device intended to level the volume on a TV so commercials are not super loud compared to the program. These are readily available and not expensive. They are stereo, i.e. two audio channels and usually are RCA phono plug in and out. The ones I have used have a control to adjust how aggressive the leveling is. Turned way up there are few amplitude dynamics left in the audio. 73 Patrick AF5CK -Original Message- From: Robert Logan Sent: Wednesday, December 19, 2012 7:20 PM To: David Edwards Cc: flexradio@flex-radio.biz Subject: Re: [Flexradio] Need AVC Various older Handbooks, including my 1962, have a simple circuit of diodes to lessen nearby blasts of audio. It's called a noise limiter, and works between the audio out and the headphones on the principle of diode current limiting. Not an AVC circuit but it may help. Bob, NZ5A Sent from my iPhone On Dec 19, 2012, at 7:08 PM, David Edwards w...@verizon.net wrote: Is there anyway to implement an AVC on the flex 5K? I am using 5K, powerSDR 2.5.3, and windows 7 64 bit. When listening to weak DX that is near the noise floor and loud stateside stations calling your ear drums get blown out when the locals are calling. The AGC raises and lowers all boats. Need an AVC, Maybe there is some way to put one between the Flex and the speaker, anyone know of such a device? thanks de WB1S ___ 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/
Re: [Flexradio] Need AVC
On 12/19/2012 8:08 PM, David Edwards wrote: Is there anyway to implement an AVC on the flex 5K? I am using 5K, powerSDR 2.5.3, and windows 7 64 bit. When listening to weak DX that is near the noise floor and loud stateside stations calling your ear drums get blown out when the locals are calling. The AGC raises and lowers all boats. Need an AVC, Maybe there is some way to put one between the Flex and the speaker, anyone know of such a device? thanks de WB1S [...] It seems to me that the AGC in PowerSDR should be able to control the relative levels perfectly if you make sure that the AGC-T is all the way up, set the AGC time constant fairly fast, and ensure that there is enough preamplification (put the preamp on 'high' and even use an external RF preamp if needed) to bring the noise floor and the weak signals up to full audio level. I do extensive listening, recording, and observing of the waveform off the audio output of PowerSDR and, if you set the AGC and RF preamp aggressively enough, it can be very tightly controlled. I cannot imagine needing any post-processing to control it. 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/
Re: [Flexradio] Need AVC
Guys, this is what AGC is FOR. Older radios that had AVC used it because AGC did not work well. (ANL was just a clipper and a way of dealing with impulse noise in an AM receiver, taking advantage of how clipping the peaks greatly reduced the average power of the noise.) The trick here is to use the AGC-T opposite the way that Flex suggests that it be used. Most of us prefer the first 10dB or so to be linear so that a 10dB change in signal level translates into a 10dB change in audio level. If you do that and push the noise down, it works almost as well as DSP-based noise reduction (NR) but without the gargles and other anomalies (which drive me nuts). The point of AGC is to flatten the level response so that stronger signals do NOT sound different in level. Certainly the AGC in the Flex radios is pretty good. So here is what I suggest: rather than adjusting the AGC-T downward until you get a clear and subjective halving of the noise floor level (about a 10dB cut), I recommend you slowly increase AGC-T until you no longer hear an increase in noise level. You want your AGC threshold set right at the noise floor. This should keep everything, noise and signal, at that level. I don't like this setting because it means that I have to listen to the noise at the same level as the signal between and words (in SSB and depending on AGC speed), but it does mean that you should hear the really weak ones at the same volume level as the really strong ones. -- Brian Lloyd, WB6RQN/J79BPL 3191 Western Dr. Cameron Park, CA 95682 br...@lloyd.com +1.767.617.1365 (Dominica) +1.916.877.5067 (USA) ___ 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] Need AVC
Is there anyway to implement an AVC on the flex 5K? I am using 5K, powerSDR 2.5.3, and windows 7 64 bit. When listening to weak DX that is near the noise floor and loud stateside stations calling your ear drums get blown out when the locals are calling. The AGC raises and lowers all boats. Need an AVC, Maybe there is some way to put one between the Flex and the speaker, anyone know of such a device? thanks de WB1S ___ 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/
Re: [Flexradio] Need AVC
Various older Handbooks, including my 1962, have a simple circuit of diodes to lessen nearby blasts of audio. It's called a noise limiter, and works between the audio out and the headphones on the principle of diode current limiting. Not an AVC circuit but it may help. Bob, NZ5A Sent from my iPhone On Dec 19, 2012, at 7:08 PM, David Edwards w...@verizon.net wrote: Is there anyway to implement an AVC on the flex 5K? I am using 5K, powerSDR 2.5.3, and windows 7 64 bit. When listening to weak DX that is near the noise floor and loud stateside stations calling your ear drums get blown out when the locals are calling. The AGC raises and lowers all boats. Need an AVC, Maybe there is some way to put one between the Flex and the speaker, anyone know of such a device? thanks de WB1S ___ 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/
