Ground Loop Isolator

[EarlSuitor]

I still have a low hummmmmm in the background,

Warren County Fire and EMS Live Scanner Audio Feed

I just installed a ground loop isolator..... still humms. ARE THEY DIRECTIONAL?
Perhaps I put in on the line backwards? If so, I need to get an adapter and put it in the other way [???]

 

[DigitalSandwich]

I listened to your feed for a while, and it sounds like a 60Hz hum. If the ground loop isolator didn't fix the issue, it could be also be poor filtering on your power supply.

I also noticed that the hum and the noise floor becomes louder when the traffic ends, so I suspect there is some sort of AGC on the PC side. Disabling or reducing the max gain on the AGC may make the hum less apparent.

Without knowing your exact setup (especially power and signal routing), I can't give any specific feedback, but I hope this helps you root-cause your issue.

As for the ground loop isolator, they don't usually have in/out, since they are typically made of 1:1 isolation transformer.

N8YQX

 

[EarlSuitor]

Reply.....

I don't know how to get to the AGC to reduce the gain. Is there any chance that plugging the computer into a different outlet or a line conditioner might work?? I could try that. What do you think? I'm pretty sure the hum is coming from the computer the signal goes through, because I've tried 3 different scanners and they all do it.

THANKS,
Earl

 

[DigitalSandwich]

Based on your analysis, it does sound like the PC is at fault.

IF your sound card input has a AGC option, I think it can be accessed through the speaker icon in your system tray. Unfortunately, my PC doesn't have the AGC option, so I'm taking an educated guess.

Assuming you have Win 7,
1. Right click speaker icon in tray.
2. Click on "Recording devices".
3. Click on your particular input device.
4. Click on "Properties".
5. Look for AGC or something similar (automatic level control?).
6. You may also want to play with gain/volume within properties.

Sorry I can't be of any more help.


N8YQX

 

[EarlSuitor]

Thank you !

It's not sounding too bad now...... thanks.

 

[04Z1V6]

I had this same problem and I did everything in about the same order as you did. I ended up using a very good monster power strip, that isolated the power supply on the scanners from the power used by the computer because of the filters used in the power strips circuitry. What I had found was that there was so much noise created by other electronics on the houses power that I needed to filter out this.

 

[jsncrso]

Best thing is to eliminate the ground plane period. Half the reason I chose a thin client PC as my server is that it runs from an AC-adapter and doesn't have a grounded chassis. Same with my scanner. Grounds outside of a controlled setting are horrible for noise. Ground loop isolators will isolate the ground plane, but can still readily transmit noise since they are nothing more than 1:1 transformers.

There is not one iota of noise on my feed due to the way I have set up and designed my setup.