I posted a hyperlink to the exact Radio Shack UVSJ that has power pass on the UHF side. You'll have to order it from an Ebay seller (that's where I got mine, as my local RS store wanted TWICE the price for it!), or find a Radio Shack that still has one. Or, you can order one from an Amazon seller, or buy the model that Rabbit posted a link to.
As for disconnecting the preamp you presently have to try that option, you
must take it
out of the circuit completely. Just disconnecting power to it doesn't bypass it.
Personally, IF you want to try just replacing the preamp and leaving everything else the same, the Kitztech KT-200-Coax model may be your best bet. I
originally ran both my UHF and VHF antennas through that method (up until this last weekend) like Rabbit's "Test 3", and it seemed to work just fine with the Kitztech with NO overloading that I could tell.
Here's a link to the cheaper Pico UVSJ to put right after the UHF antenna.
http://www.solidsignal.com/pview.asp...UVSJ%29&q=uvsj
The EZHD antenna may work ok for you for VHF only, IF you run it through the VHF side of a UVSJ to filter out UHF signals.