From: MICHAEL SMITH <kb8wlw@me.com>
Date: 2010/05/04 Tue AM 10:12:47 PDT
To: app_rpt-users@qrvc.com
Subject: [App_rpt-users] Noise Problem with URI and Voter Comment
Sorry guys I just realized when I was hitting reply, I was replying directly to the individual. I would guess proper etiquette would be to email the group. Or at least CC the group.
Thanks for all of the suggestions, I will try adding in a resistor or a voltage divider. I will have to check to see if I have a 1:1 transformer laying around. And yes the "RADIO TUNE TXVOICE" was on the far low side. I will also double check to see if the monitor is creating the noise by turning it off.
I thought the same thing (regarding local HT noise) and hooked up the audio input leads to the audio path and seen this (hopefully I can attach a picture). I also had someone off site confirm they heard the noise. I did not think about trying to figure out the frequency.
Looks like coherent noise from the 1ms interrupts Asterisk uses. Probably sounds like a raspy 1kHz tone. Try the voltage divider first. Your scope picture shows 10mV of noise (assuming a x1 probe ad 2mV/div). I'd try a 20:1 voltage divider ratio. BTW: The 1:1 transformer will not help as the ground from the URI still needs to be connected to the radio for proper operation of the control signals COR and PTT and the isolation action of the 1:1 xfmr will be defeated.
Another approach would be to drive the TX modulator directly and not use the mic input.
Steve
WA6ZFT
replyAll (1.04 KB)
reply (146 Bytes)
I finally had time to try some things out, I was able to get rid of the noise by putting some resistance. Actually I put in a POT and set the RADIO TUNE TXVOICE just above mid range. Then I used the pot to adjust the deviation. I ended up with around 6k of resistance. When I have more time I will adjust the RADIO TUNE TXVOICE to mid point and do the same test.
Thanks to all!
Mike / KB8WLW
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On May 4, 2010, at 1:46 PM, hwstar@rodgers.sdcoxmail.com wrote:
From: MICHAEL SMITH <kb8wlw@me.com>
Date: 2010/05/04 Tue AM 10:12:47 PDT
To: app_rpt-users@qrvc.com
Subject: [App_rpt-users] Noise Problem with URI and Voter Comment
Sorry guys I just realized when I was hitting reply, I was replying directly to the individual. I would guess proper etiquette would be to email the group. Or at least CC the group.
Thanks for all of the suggestions, I will try adding in a resistor or a voltage divider. I will have to check to see if I have a 1:1 transformer laying around. And yes the "RADIO TUNE TXVOICE" was on the far low side. I will also double check to see if the monitor is creating the noise by turning it off.
I thought the same thing (regarding local HT noise) and hooked up the audio input leads to the audio path and seen this (hopefully I can attach a picture). I also had someone off site confirm they heard the noise. I did not think about trying to figure out the frequency.