usb radio config file

App_rpt-users
1

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

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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

2

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

ยทยทยท

-----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

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App_rpt-users mailing list
App_rpt-users@qrvc.com
http://qrvc.com/mailman/listinfo/app_rpt-users