A quality preamp will run about $35 - $60 and a quality rotor about $65 - $90.
I haven't seen a lot of discussion on rotors here. Maybe I haven't looked hard enough. I've used all sorts of rotors since 1968 so I have some strong opinions on them. I'm not a fan of these inexpensive (<$150) TV rotors for a couple of reasons. 1) They have no real bearings in them so unless you live in a very low corrosion environment they tend to seize up or bind after a couple of years. They really need to be taken down, cleaned up and greased every so often. Who wants to do that? 2) The 3 wires going to the rotor only supply voltage to the motor. There is no positional feedback. The accuracy of the pointing depends on the rotor turning the correct amount in the expected amount of time. That's how the indicator box stays in sync with the antenna position. If for any reason the antenna does not turn completely freely, the antenna and the indicator box get out of sync and you have to perform the sync procedure. Even brand new rotors have this problem. The only positive thing I have to say about these rotors is that they do seem to be capable of turning a TV antenna.
Once upon a time there were a couple of decent rotors that were not extremely expensive. The Alliance U-100 was the standard TV antenna rotor although it did have some sync issues but not as bad as today's rotors. A step up from there was the Alliance HD-73 which was remarkably inexpensive for a rotor with real positional feedback. If you can find one today used, I'd still recommend getting it. In light duty use they essentially never break. The only thing that happens to some of them is that a small disk of cork inside the rotor used as the brake can become stuck and prevent the rotor from turning. This is easily repaired with no replacement parts and the bearings can be cleaned and greased.
Today if you want a rotor that will last for years with no issues you need to buy a low end ham rotor. The least expensive one is the Hygain AR-40 and it comes with the lower mast mounting bracket. The next one up is the Yaesu G-450 with optional lower mounting bracket. The only thing I don't like about these rotors is that they use AC voltage to run the motor so they have a large non polarized capacitor. In the past it was common for that capacitor to go bad with disuse and the rotor wouldn't turn. I don't know if the quality of the capacitor has improved these days. These rotors are in the $320 - $400 range without rotor cable.
My favorite rotor right now is the Yaesu G-800SA but with the lower mast mounting bracket and shipping it'll be close to $500. It uses DC to run the motor so no capacitor issues. A DC run rotor can sit for a year unused and will work the next time it's turned on. The catalogs say it requires 6 wire rotor cable but after looking at the schematic I found it'll run on 4 wires which is what I do. After 9 years of heavy duty use I've run into some problems with the pots in the rotor and the control box used for the position indicator causing an unstable pointer in some directions. But I've turned that rotor tens of thousands of times running all sorts of TV antenna tests plus for general ham radio use. No average person watching TV would use it that much in a lifetime. It still turns 10 sq. ft. of antennas with no issues despite the unstable indicator.
One issue with the ham rotors is mast size. For example the G-800SA minimum mast size is 1.5" so the cheap 5' long 1-1/4" antenna mast can't be used.
ChuckEdited by Calaveras - 7/8/12 at 3:15pm