No, they don't cancel out the signal.  Main reason they are quieter is 
they are a dc grounded antenna.  Take a look at tv antennas, almost all 
driven elements are folded dipoles.  The only way you'd cancel out the 
signal is if you had something 180 degrees out of faze.  Of corse when 
you put signals in faze, you get gain which is what makes fazing 
verticals work.
73s
Butch Bussen
wa0vjr

On Mon, 25 Aug 2008, Bob Tinney wrote:

> Hi,
> I have always heard that a folded dipole is quieter than a standard dipole,
> but I've always wondered if the two wires in the folded dipole would not
> only cancel out the noise, but would they also cancel out some of the
> signal.  Has anyone ever compared the two antennas side by side?
> 73
> Bob Tinney, K8LR, [log in to unmask]
> Skype, bobtinn
> from a guy that knows everything about nothing,
>     and nothing about everything!
>
> ----- Original Message -----
> From: "Louis Kim Kline" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Sunday, August 24, 2008 10:42 PM
> Subject: Re: G5RV VS Windom
>
>
> What about a folded dipole?  They are usually quieter than a standard
> dipole.  If a delta loop isn't practical, then a folded dipole might be the
> next best thing if you are looking to quiet down the noise.
>
> --Lou K2LKK
>
>