[TenTec] balun noise?

[Denton]

Not really a ten tec question...but this little group seems to be 
particularly knowledgable...
I am tinkering with an 80 meter inverted L antenna, and I noticed that when 
I hook up any kind of balun at the feedpoint, the signal to noise is much 
more prevalent than when feeding the L directly with coax.
The L has a few radials attached and shares a common ground rod with the 
radio station ground.
Wonder whythe worse signal to noise. Thanks...