Yep it does work but not so much as to pay big bucks for it...
I had a coil I made in my junk box and a 250pf variable so I tossed them together to see what would happen when I connected it to my 200 foot single radial...
It did tune out electrical line noise from the power company lines about 2 db... not great but now I can hear some thing down on 75 meters which is all I asked of it... so I giv3e it a 5 on the joy level ;-)
I used the coil for BCB not amateur as the 200 foot radial is 'long' vs 75 meters. the variable is connected in series with the radio ground and the long radial...
The radial is just speaker wire run to the back of the apartment, out the door and down a side wall to the front of the apartment. It soon will be hidden with flower beds that I always use to hide such things. The apartment owner doesn't realize that I have a 'hidden' motive behind making the area grounds looking better ;-) In this situation one must use what works for them ;-)
73 Vince
KA1IIC