I used a similar device a couple of summers ago,made by MFJ, when I had some broadband noise. In my case, I found that a shorter antenna (a wire) of about 25 feet long worked best. My antenna at the time was a 65 ft long wire antenna. It worked well, and I was able to null the local noise several dozen DB down. It was not perfect, but it made the difference between not hearing anything, and being able to hear strong and medium strength signals.
I fed my noise antenna with coaxial cable, and was not particularly careful about its placement..it worked OK. I tried making another longwire antenna that was closer in size to my "real antenna". It did not seem to help much====if any in my case.
I recall that fiddling with the knobs and switches was always a project. My settings would vary from one day to the next even if I was on the same frequency. It took patience to set it up correctly....and I frequently had to adjust slightly a few hours later.
Universal has the manual for this on line:
http://www.universal-radio.com/catalog/preamps/0094om.pdf