The H-shaped antenna will give you direction; with calibration for intensity, it could give you a rough idea of location on its own. You could place a pair of the H-antennae a known (smalll) distance apart to increase your precision, or place them a larger distance apart and look at where their directional lines cross. For example, if one points east and one points north, then it’s clear that there’s only one (nearby) place the Fiend can be. Lastly, you can use multiple “intensity-only” antennae to locate the Fiend, by drawing overlapping circles on a map. Two such receivers will narrow the Fiend’s location to two possible points; a third receiver that’s not collinear with the first two will pare your options to one. Additional receivers are overkill, but give you better precision.
A GPS receiver attached to the Fiend is nice, but it’s an unnecessary complication. If you gather the GPS data on-board a Fiend Finder, you have to transmit it from the Fiend (to the Hero) for it to be of any use. At that point, why not just transmit “beep beep beep” and use the above methods? The bonus here would be that you get data accurate to within 3m of your target, and your Hero doesn’t have to know his own location or even follow along. If your transmitter includes a pager or a phone instead of a radio, you could even SMS-Text message the location to an e-mail account. So there are advantages, but you pay for them in complexity. Unless you’re keeping a detailed log of the places your Fiend visits to build a court case, and intend to keep surveillance running continuously for days or weeks, adding GPS isn’t really worth it.
Another option is to passively home in on a known signal emanating from your Fiend (eliminating the need to place a bug). Using the “multiple intensity-only antennae” method from above is even more helpful when you realize that (a) such antennae already exist, and (b) most people carry around a transmitter keyed for these antennae anyway: cell phones! If your Fiend’s phone number is known, it is technically possible (although non-trivial) to compromise cell phone towers or enlist the aid of the phone companies to triangulate a phone’s location. With enough towers, you get triangulation that’s as good as the local cell network. No good in Iraq, but pretty good in the U.S., Europe, or Japan. “What if the phone is off?” you ask. I had heard that it used to be possible to activate parts of a cellular phone (like the microphone) remotely without the user’s knowledge. YMMV - I think you’d probably have to be a government agency or similarly well equipped (spy/right-wing conspiracy/black ops team/Batman) to pull this off.