[App_rpt-users] Strange oscillation

[Scott Weis]

I have had strange audio problems on the URI when the usb port is acting up
or failing. I changed ports and it went away. 

-----Original Message-----
From: app_rpt-users-bounces at qrvc.com [mailto:app_rpt-users-bounces at qrvc.com]
On Behalf Of Shawn Hastwell
Sent: Tuesday, August 17, 2010 10:58 PM
To: app_rpt-users at qrvc.com
Subject: Re: [App_rpt-users] Strange oscillation

On Tue, Aug 17, 2010 at 10:42 PM, Stephen Rodgers <sales at qrvc.com> wrote:
> kb8ude at gmail.com wrote:
>> I am still testing my hardware here on a dummy load and having strange
behavior.  First, my hardware:
>>
>> Dell P3 1.13GHz server, 1gb RAM, 36gb SCSI drive, installed via ACID CD.
>> URI interface, output cable about 6 inches long, twisted but not
shielded.
>> Motorola Radius M120 UHF turned down to 20W.  Set as a simplex link and
the channel is set to carrier squelch.
>>
>> Set my audio levels using a Motorola service monitor.
>>
>> Sometimes when the radio transmits I get clear voice.  Most of the time
there is a noticeable low frequency oscillation on the signal and the audio
is unreadable. Almost sounds like mid-rpm engine ignition noise if that
helps paint a cleare picture of the sound.  RX seems good, I am listening
using iaxrpt on the pc and can hear myself slightly delayed and clear.
>>
>> I tried a couple ferrites on both sides of the URI with no change.  I
also noticed that sometimes the 'connected' announcement has a ripping or
tearing sound to it as well as stuttered courtesy tones on occasion.  I am
wondering if my server just isn't fast enough or if the URI needs a 2.0 USB
port to plug into.
>>
>> Any thoughts folks?
>>
>> -Shawn
>>
>> Sent via BlackBerry from T-Mobile
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>>
>
> Slow PC: If you run the 'top' command from the linux shell command line,
how much CPU is being consumed by asterisk?
> More than 25% is asking for trouble. Try a faster pc and see if it clears
up the problem.
>
> Audio oscillations: It's hard to say what might be wrong. This could 
> be CPU speed related, interface adjustment related, or a 
> grounding/ground loop issue. It wouldn't hurt to look at the URI audio
output with the scope in your service monitor while it is oscillating.
>
> BTW: Ferrites are no good at reducing noise at audio frequencies.
>
> Steve
> WA6ZFT
>

I am still getting used to the service monitor and how to do various things
with it properly.  I will see what I can do in that regard.

TXVoice and TXTone are at 300 and 175 respectively.

I did a 'top' while there was audio activity connecting and disconnecting
from the Echotest server.  It peaked near 22.3 and only one time at 24.8.

I was thinking RF may have been affecting the URI, hence the ferrites.
 I am not ruling out the radio as the cause directly though, I understand
that some of these models will exhibit some erratic behavior when turned
down too far based on the rated average power.  I am going to turn it back
up to it's rated power and see what happens as well.

-Shawn
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