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  #21 (permalink)  
Old 07-20-2011, 5:15 PM
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Quote:
Originally Posted by ProScan View Post
The hum is caused by a ground loop. Go to RS and get an audio isolation transformer. Your problem will be cured. Guaranteed.
This is classic 60Hz hum. He may have some noise by ground loop but all signs point straight to 60Hz hum. You guys need to stop leading him astray.
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  #22 (permalink)  
Old 07-20-2011, 7:30 PM
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Originally Posted by jwjkp View Post
This is classic 60Hz hum. He may have some noise by ground loop but all signs point straight to 60Hz hum. You guys need to stop leading him astray.
I'm not. I think you are by suggesting a power supply. This is a classic problem connecting audio sources to different grounds. The AC adapter that comes with the scanner is good enough.
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  #23 (permalink)  
Old 07-20-2011, 8:01 PM
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Originally Posted by ProScan View Post
I'm not. I think you are by suggesting a power supply. This is a classic problem connecting audio sources to different grounds. The AC adapter that comes with the scanner is good enough.
Well he will find (and probably attest to eventually) that it is 60Hz hum and ONLY using a different power supply, like the one I linked to, will solve it.

I know this because I had his same issue and thought the same you did. I was dead wrong.
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  #24 (permalink)  
Old 07-21-2011, 9:15 PM
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I had a radio that would hum in the 470. frequency range to the point I couldn't stand it any longer. Turned out to be the wall wort.
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Old 07-22-2011, 6:47 AM
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Quote:
Originally Posted by DavidQT69 View Post
Well It's definitely NOT a problem of someone transmitting on the same frequency because I'm broadcasting an 800-Trunked system for a Police Department so there's no way someone else is transmitting on there besides Police... Another thing is I am leaning more towards a power problem that was suggested about the 60-hz thing because when I don't use a power supply and just use batteries there's no hum at all, it only hums when I plug it in the wall. The only thing I don't understand is I bought that power supply from Radio Shack along with the scanner I bought from there because that is the only power supply RadioShack has that powers this particular scanner...
you can buy radio's that can be programmed for that frequency all you would need is a wide band vhf radio that can send and receive pl tones is an audible tone transmitted when the user presses the transmit button on the radio this activates all other radios on this frequency a device like this sells for around $100 - $200 your best bet is just to check everything and to take Necessary steps to fixing the problem.

besides if you couldn't on the frequency it would mean that that frequency is encrypted then you wouldn't be able to receive communications on that frequency either.

i have been setting up vhf and uhf networks for some time now

anything is possible

Last edited by absarjames; 07-22-2011 at 6:57 AM..
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Old 08-30-2011, 12:36 AM
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Hey guys I just wanted to update y'all on my "humming" situation... I FINALLY was able to plug in the wall adapter into my scanner and not hear a hum anymore on my feed... Turns out the problem was I was using a stereo cord for my scanner-to-mic input on my laptop, I switched to a mono cord and it's perfect now, listen for urself! Thanks to all for ur helpful advice!


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  #27 (permalink)  
Old 09-18-2012, 9:13 PM
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I seem to be getting this hum on my feed that has been discussed here.

I went out, bought a 13.8VDC switching power supply with cigarette lighter adapter.

It got rid of ALOT of my hum, theres still a small hum there, but again when I unplug my power source the hums totally gone,

I am going to get a ground loop isolator, im also running a stereo 3.5mm cord and not a mono cord.

Any other suggestions?
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  #28 (permalink)  
Old 09-18-2012, 11:34 PM
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Your on the right track with the Ground Loop isolator, This should take care of your issue. However give it a try and if the problem still exists we will help you make it right.

Sometimes the cords that are used to connect the scanner audio to the computer, are not well shielded this will allow noise to enter the sound card of the machine thus also creating the hum.

Hope this helps.
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  #29 (permalink)  
Old 09-19-2012, 7:44 AM
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Quote:
Originally Posted by smittyj77
I seem to be getting this hum on my feed that has been discussed here.

I went out, bought a 13.8VDC switching power supply with cigarette lighter adapter.' still a small hum there, but again when I unplug my power source the hums totally gone,

I am going to get a ground loop isolator, im also running a stereo 3.5mm cord and not a mono cord.

Any other suggestions?
Read the post above re: stereo cord.
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Last edited by W8RMH; 09-19-2012 at 7:46 AM..
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  #30 (permalink)  
Old 09-25-2012, 4:05 PM
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I fixed hum noise by adding a common ground between radio and machine. just a piece of wire clipped to the antenna and computer chassis.
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  #31 (permalink)  
Old 12-15-2012, 7:46 PM
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I'm very grateful for this radio reference forum! I recently fired up my trusty old pro-2037 scanner and it worked fine except produced this exact same 60Hz hum on my feed. I could not hear the hum locally but it was obvious on the internet feed. I immediately assumed that this was a ground loop and installed a ground loop isolator onto the feed. It made not a bit of difference!

So I took a booster pack with a 12 volt outlet and fed the scanner with this for power. The feed ran silent and clean. No 60Hz hum possible with a DC supply but it bothered me why it would be this way. So I experimented further.

Tried a mono cord in place of the stereo version, still hum. Tried running a common ground wire from my computer chassis to the scanner. Still hum. but I finally fixed it. Guess how?

Replacing the capacitors on the power supply rail! It makes sense to me. The scanner was made over ten years ago. I changed only two caps, both rated at 1000 microfarad and the feed is now silent even when fed with AC power.

Thanks to this thread all of the answers were provided. You guys are awesome.
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  #32 (permalink)  
Old 12-16-2012, 12:25 PM
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Quote:
Originally Posted by DavidQT69 View Post
Does anybody know how to get rid of the "humm" that is broadcasting over my feed? It's been there for the longest time and I have no clue how to fix it. It's worse when I have my scanner plugged into the wall so I have to run my feed of rechargeable batteries so it doesn't make audio issues, but there is still humming, does ANYBODY know the problem and how to get rid of it? I would appreciate any help... Thanks!
Please see here: How to Maintain a Good Feed
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  #33 (permalink)  
Old 12-19-2012, 8:43 AM
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Quote:
Originally Posted by lowerrollin View Post
I fixed hum noise by adding a common ground between radio and machine. just a piece of wire clipped to the antenna and computer chassis.
This worked for me too, got rid of 90% of the hum.
Probably will still add isolator anyways.
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  #34 (permalink)  
Old 12-25-2012, 10:47 AM
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Even good power supplies can have 60 cycle hum on their DC output. I just found a bad Astron RS 12 power supply that was ripping up a 470 mhz receiver front end. This was the 2nd Astron I've seen do this and it was the last thing I suspected as the culprit.

You can check for 60 cycle with an O-scope, if you have more than .25 volt AC on the DC output you're gonna hear it usually in the audio. Same for car alternators when the diodes start to break down, you hear the weeeeeeee weeeeeee sound that rises and falls with engine RPM in your stereo or CB.
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  #35 (permalink)  
Old 12-26-2012, 9:21 AM
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Quote:
Originally Posted by spectr17 View Post
Even good power supplies can have 60 cycle hum on their DC output. I just found a bad Astron RS 12 power supply that was ripping up a 470 mhz receiver front end. This was the 2nd Astron I've seen do this and it was the last thing I suspected as the culprit.

You can check for 60 cycle with an O-scope, if you have more than .25 volt AC on the DC output you're gonna hear it usually in the audio. Same for car alternators when the diodes start to break down, you hear the weeeeeeee weeeeeee sound that rises and falls with engine RPM in your stereo or CB.
For those of you who don't have a scope, can also check for the amount of AC ripple on your DC with a regular DVM set on the AC setting. (old trick from my analogue DC drive days)
FYI a tech. I apprenticed under years ago first step in any kind of electronic repair was to replace all the Caps. It was amazing what that fixed and 9 times out of 10 electronic problems were power supply related.
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  #36 (permalink)  
Old 12-26-2012, 6:31 PM
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Thanks gfdfortynine, forgot to mention the easy way to test the line without a scope.

I just fixed my hum problem with a ground loop isolator from Rat Shack. I didn't want to wait for the one on ebay that had stereo jacks on both input and output for $10. This Rat Shack one only has a stereo plug on one side and RCA jacks on the other so I had to add in a Y adapater with RCA female to 3.5mm stereo plug male

Part # 270-054 ground loop isolator - cost $20
Part # 274-369 Y adapte,r 3.5mm stereo to RCA - cost $4

No more hum or thump at the beginning or end of a transmission.
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