From: "David Powell-Williams" <dpowellwilliams@shaw.ca> Date: 2010/01/05 Tue PM 03:26:26 PST To: <app_rpt-users@qrvc.com> Subject: [App_rpt-users] usb radio config file
<snip> Second issue: The loudest playback sounds cause the URI to go into saturation and distort. I may not have calibrated the levels very carefully, but even if I manually lower the txlevel setting from 800 down to, say, 300 it still distorts - it's just a quieter distortion. What can cause this? <snip>
I have the same problem with a modified CM108 usb installation.
After setting all the 'radio tune' parameters, there is serious distortion on voice modulation peaks, irrespective of the source being Iaxrpt or another node.
However, the 'radio tune txvoice' generates a perfect sine wave at 3 KHz deviation, as seen on an oscilloscope at the exciter modulator or on a service monitor off-air. I am using duplex=0 in rpt.conf since the node operates simplex.
Dave VE7MQ 2140
_______________________________________________ App_rpt-users mailing list App_rpt-users@qrvc.com http://qrvc.com/mailman/listinfo/app_rpt-users
I have not seen this on a properly configured system. Chances are it has to do with de-emphasis configuration on the receive side, or pre-emphasis/limiting (prelim) in the transmit side) Where is the audio getting distorted? Transmit or receive? so you see the distortion on the TX line or RX line if you look with a scope? You might be able to determine where it is getting distored by connecting your node to a working node you can monitor, then send audio both ways. Disclaimer: I offer URI support and suggestions as a courtesy only as I do not derive any income from sales of the URI. I am in no way obligated to provide support at any level. Steve WA6ZFT
subsequent experimentation seems to indicate that if you set txprelim=yes the audio overloading of the CM108 goes away. I guess you get pre-emphasis AND limiting or nothing at all which is too bad because even though it says ; no - Audio is not pre-emphasized and limited. ; Suitable for use on a microphone input once the signal has been trashed, it is not really suitable for anything, especially a microphone input. a better wording might be Audio is not pre-emphasized and NOT limited if audio level exceeds D/A dynamic range it will be severely distorted. the user needs to make sure that levels do not exceed the maximum warning: some of the pre-recorded GSM files exceed the maximum It would be nice if there was an option for limiting with no re-emphasis ... Ken -----Original Message----- From: hwstar@rodgers.sdcoxmail.com To: David Powell-Williams <dpowellwilliams@shaw.ca>; app_rpt-users@qrvc.com Sent: Tue, Jan 5, 2010 6:55 pm Subject: Re: [App_rpt-users] usb radio config file
From: "David Powell-Williams" <dpowellwilliams@shaw.ca> Date: 2010/01/05 Tue PM 03:26:26 PST To: <app_rpt-users@qrvc.com> Subject: [App_rpt-users] usb radio config file
<snip> Second issue: The loudest playback sounds cause the URI to go into saturation and distort. I may not have calibrated the levels very
carefully,
but even if I manually lower the txlevel setting from 800 down to, say, 300 it still distorts - it's just a quieter distortion. What can cause this? <snip>
I have the same problem with a modified CM108 usb installation.
After setting all the 'radio tune' parameters, there is serious distortion on voice modulation peaks, irrespective of the source being Iaxrpt or another node.
However, the 'radio tune txvoice' generates a perfect sine wave at 3 KHz deviation, as seen on an oscilloscope at the exciter modulator or on a service monitor off-air. I am using duplex=0 in rpt.conf since the node operates simplex.
Dave VE7MQ 2140
_______________________________________________ App_rpt-users mailing list App_rpt-users@qrvc.com http://qrvc.com/mailman/listinfo/app_rpt-users
I have not seen this on a properly configured system. Chances are it has to do with de-emphasis configuration on the receive side, or pre-emphasis/limiting (prelim) in the transmit side) Where is the audio getting distorted? Transmit or receive? so you see the distortion on the TX line or RX line if you look with a scope? You might be able to determine where it is getting distored by connecting your node to a working node you can monitor, then send audio both ways. Disclaimer: I offer URI support and suggestions as a courtesy only as I do not derive any income from sales of the URI. I am in no way obligated to provide support at any level. Steve WA6ZFT _______________________________________________ App_rpt-users mailing list App_rpt-users@qrvc.com http://qrvc.com/mailman/listinfo/app_rpt-users
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Ken