RF interference 300 DR

Posted by: BPou on 07 February 2017

Hi, I am having RF interference in my system. I completely disconnected my 272 from the 300 but still can hear a radio station if I put my ear to the twitter. This makes me believe that the RF is not coming through the pre. If I turn the amp off the RF disappear. If I disconnect the speakers cable from the amp, it also disappears.

I checked the electrical connections too. The voltmeter is reading less than 1 v between ground and neutral and 117v between hot and neutral, which means that the connection is well grounded.

It looks that the 300 is catching RF somehow. How can I solve this problem? Your inputs are highly appreciated. I am running out of ideas.

Posted on: 15 February 2017 by Ron Toolsie

Well, the wavelength of 100MHz (the 'left' side of the dial, where NPR stations reside) is around 3m. Maybe your speaker cables are uncomfortably close to some integer multiple of a half-wavelength. I have actually used a 5.5m length of NACA5 as a FM antenna plugged into the back of a NAT01 and got full signal strength.

One thing worth trying-if only to see if it makes a difference-is to shroud all Burndy cables in a wrap of aluminum foil. This has actually worked in extreme cases, but the WAF factor is in negative numbers. But if it works, it will at least tell you the portal of entry.

If that doesn't work-buy a NAT01 tuner and tune it to the signal that is breaking through. That way at least the noise will be correlated with the signal.