For Hamfest type walking foxhunts, I prefer to use the Ramsey DF'er.
On two meters, it seems to be an outstanding unit. In several foxhunts, I have seen people using beams and other equipment chasing reflections all over the hamfest grounds. But, the Ramsey unit has usually directed me right to the hidden transmitter.
The only exception has been when the fox has been hidden in a metal building with wires strung all over the room.
Also, on 440mhz, it is virtually worthless because the antennas are spaced too far apart.
This unit works by comparing the phase of an FM signal received by each antenna. It generates a tone based on the difference in phase between the two. The louder the tone, the larger the difference in phase between the antennas. Thus, when the tone goes away, the signal source is perpendicular to the plane of the antennas
The unit also has LED's indicating whether it needs to be turned left or right to become perpendicular to the signal.
Another great feature is a meter that indicates the difference in phase between the antennas. This is extremely helpful when you are within a few feet of a well-hidden transmitter. By zeroing this meter, you get a very precise pointer to the fox.
If anyone in the Central Indiana area is interested in one of these, but is unable to do the soldering work, I would be willing to do all of the soldering for them. I have built three of these so far.
For more information on this kit, check under Receivers & Converters at Ramsey's Web Page