If I knew T-Hunters were using Dopplers I'd put my hidden T antenna horizontal negating the effectiveness of heir Doppler use as vehicle Doppler RX antennas are vertical.
Doppler mobile/vehicle use requires a strong signal >S6 for direction and relegated to forward/aft-port/starboard of the vehicle while the vehicle is moving to allow visual averaging of reflections. Dopplers are of little to no use on weak signals.
I did use a Doppler, for a short time when going after repeater problems when speed is of the essence in finding these problems. Since I was the driver/hunter I found I could not study the Doppler while driving safely in Southern CA traffic.
I found it much easier to become proficient at using my 2m 3element special T hunt Quad. One of the keys to my success was using my design/built external noise/S meter. I placed it directly in front of me on the dash but the real key was incorporating an audible tone speaker that parroted the meter response, stronger the signal the higher the audible tone. The other key was my two step built in attenuation built around controlling the B+ of the radio's 1st RF mixer; one step removed the B+ to the base & the other step 10K variable pot to control the collector B+. This was needed to keep the external meter displays centered and not pegging/saturating the meter/circuit.
Sometimes I could psych myself into thinking I was close to the Fox/T ; to keep me in perspective I placed a HT on my dash removing the rubber-duckie (helical dummy load), set the HT to just barely squelch out full volume. If this HT started to bark at me I knew I was within 1/4mi or closer and usually I was already switching in first step of radio attenuation.
I've been thinking about trying a Doppler again, but the issue I always found was the cumbersome mediocre antenna system was less than adequate. For my next Doppler I'm going to make each of the four antennas 1/2wave dipole (like Adcock Sys). Now the trick will be how high off the vehicle does it need to be to negate vehicle metal/field affects?
The techno fun of T hunting!