Uniden 125XLT Humming from pc line in, Caused by Loft Antenna.. Help Please

[Ghostrunner-Bax]

Hiya Guys.
So heres my problem. I have a Uniden 125xlt scanner which is connected to a Diamond D-777 Antenna in my loft.
The scanner works fine with the Antenna and i have no problems atall, But i decided that i wanted to connect my Uniden 125xlt to my Pc through the line in using a 3.5mm jack on the back of my pc so i can record the audio from the scanner.

Now heres the problem im having. When i try to listen to the audio on my pc from my scanner, i get this Humming sound when the scanner is quiet, infact even if i switch the scanner off the humming still persists.
So i did what we all would do and double check all cables and pc driver for being upto date, even did some googleing to see if i could find a solution for my problem but nothing jumped out at me apart from maybe needing to buy a grounding loop isolator.
So i took hold of my scanner and just decided to disconnect the loft antenne from the scanner and the Humming just stopped!. So i connected wattson super gainer and no Humming ( untill i touch the antenna conector and it starts to hum).

By the way: the humming im talking about is only audible through my pc headphones and not the uniden speaker on the front of the scanner.

So i figured the Loft antenna is causing this Humming sound that im picking up on my PC.
So guys, how do i solve this problem?.

Thanks in Advance.

 

[doctordialtone]

, how do i solve this problem?

Lots of people, including me, have had luck using a Ground Loop Isolator.

Works like a champ!

 

[Ghostrunner-Bax]

Lots of people, including me, have had luck using a Ground Loop Isolator.

Works like a champ!

Thats what i was looking at before i discovered the antenna was the problem.
Well thats great news i will order one today.

Thanks Doc .

 

[a417]

So i figured the Loft antenna is causing this Humming sound that im picking up on my PC.
So guys, how do i solve this problem?.

You move the loft antenna away from the electrical wires... in the loft.

 

[Ghostrunner-Bax]

You move the loft antenna away from the electrical wires... in the loft.

The antenna isnt near any electrical wires, i made sure of that before i installed it.

 

[vagrant]

You figured it out already in that you need a ground loop isolator. I use this one for $10 from Amazon.

Amazon.com

 

[donc13]

Hiya Guys.
So heres my problem. I have a Uniden 125xlt scanner which is connected to a Diamond D-777 Antenna in my loft.
The scanner works fine with the Antenna and i have no problems atall, But i decided that i wanted to connect my Uniden 125xlt to my Pc through the line in using a 3.5mm jack on the back of my pc so i can record the audio from the scanner.

Now heres the problem im having. When i try to listen to the audio on my pc from my scanner, i get this Humming sound when the scanner is quiet, infact even if i switch the scanner off the humming still persists.
So i did what we all would do and double check all cables and pc driver for being upto date, even did some googleing to see if i could find a solution for my problem but nothing jumped out at me apart from maybe needing to buy a grounding loop isolator.
So i took hold of my scanner and just decided to disconnect the loft antenne from the scanner and the Humming just stopped!. So i connected wattson super gainer and no Humming ( untill i touch the antenna conector and it starts to hum).

By the way: the humming im talking about is only audible through my pc headphones and not the uniden speaker on the front of the scanner.

So i figured the Loft antenna is causing this Humming sound that im picking up on my PC.
So guys, how do i solve this problem?.

Thanks in Advance.

Several things, the cable to your loft antenna is probably NOT grounded (the outside coax braid). I would also guess you are plugging your headphone jack output into your PC's "line in" or "microphone" jack. Neither of those input jacks is designed to take speaker output, the audio level is way off what those jacks are designed for. Third, what you are hearing is "classic" ground loop noise.

Definitely get a ground loop isolator.
Try to ground your antenna cable
BE very careful on volume level on the scanner, you don't want to overload your PC's audio system.

 

[a417]

The antenna isnt near any electrical wires, i made sure of that before i installed it.

Is your cabling crossing electrical wires at right angles, or is it running parallel to it for any length?

 

[prcguy]

The hum is usually caused by a ground loop where the computer and antenna are at a different ground potential and there is a little AC current flowing in the coax trying to equalize the potential. This is where a ground loop isolator will help. If the antenna is completely floating and not grounded that would be interesting and would take some troubleshooting to figure out. If they run near fluorescent lights then the ballast transformers can emit a very strong EMI.