Interference - Electromagnetic?

[Ascii2]

I have been trying to record audio from an AM radio station and have had problems.

While tuned to the desired station, I cannot distinguish voice sounds. All I hear from radio device is a constantn "ehrrrrrrrrrrrrrr" sound.

After turning off nearby CRT monitor, audio is much better. Sounds of voices may be heard, but with a constant "ooooooooooo" sound.

After turning off nearby computer (but not as near as the monitor), audio sounds clear.


I would appreciate help with this.

What is the problem and how can I fix it?


Extra information that may be helpful:Radio device is a Bose brand system.
Radio is connected to sound card via Line-In.
I am using a Creative Sound Blaster Live 5.1 Digital sound card.
I am using Windows 2000 Professional with Service Pack 4.

[Gnufsh]

SOunds like emi, definately. It might be straight through the air, but gounded cases should provide soem shielding. It may also be in your power lines, in which case a good ups could isolate your system and radio.

[striker85]

Plus, AM is much more susceptible to intereference.

[Intrepid]

use a bigger antenna and an interment amplifier (an OPAMP in difference amplification configuration) will filter out a lot of the noise from any signal, use a gain of about 1 or 2 times if you do that. Another thing that will help is if you isolate sources of electromagnetic fields from your antenna and RF equipment, also shield the RF circuitry from the antenna, but DO NOT shield the antenna from the open air. Things that can cause an electromagnetic field is anything with electricity flowing through it, this does include the antenna, which is why you want your RF circuitry isolated from it, but not electrically disconnected, this way the signal gets picked up in the antenna but the EM wave does not also mes with your circuitry and cause distortions.