As several have pointed out the Mystery Project transmitter does not have much of an output circuit. I used a "loading coil" connected externally to the Ant tab to match a short piece of wire.
I used a piece of "Gray" PVC 2.5 inches long and wound #26 wire onto the tube until I got bored. When winding twist in a couple of taps and this will provide a fair match to  a 5 foot piece of wire. When adjusting the taps it is hard to determine resonance while monitoring collector current so a field strength meter speeds up the process.    BTW you can find "Gray" PVC in the electrical section of your local home supply store. The military ME-61 is an excellent meter and  Info on the meter and info on rolling your own meter can be found at:
http://k4che.com/ME-61/ME-61.htm