[App_rpt-users] Strange oscillation

[Stephen Rodgers]

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