That indicates that you are mis-using the term "resonant". The important thing to look for with an analyzer is the frequency at which both XL and XC are at ZERO. That is the resonant frequency. From your description of the installation, that should be at an input impedance of around 10 to 14 Ohms, which will present a VSWR of somewhere between 5 (for 10 Ohms) and 3.5 (for 14 Ohms). All 3.5 MHz 8 foot antennas similarly mounted will have input impedance close to that range (with the best being LOWER impedance -- because losses will have been minimized), and all require matching to a 50 Ohm transmitter. That match can be as simple as a tapped coil at the base of the antenna, or as complex as an autotuner like the AH-4. At 10 Ohms input impedance, you are actually capable of radiating a maximum of 10% (10 Watts) from your 100 Watt transmitter. At 14 Ohms, you are capable of radiating only 7% (7 Watts), and at 20 Ohms (fairly typical of 8 foot antenna on the bumper or trailer hitch, with a small and lossy coil), you are down to 5 Watts. All HF mobile antennas require impedance matching. You cannot simply connect them and tune for lowest VSWR. Tune the antenna for resonance, then tune the matching network for impedance match to the transmitter. If you don't want to play with those slightly interactive settings (and be limited to 10 kHz of bandwidth on 75), get a REAL autotuner -- i.e., one that mounts at the base of the antenna (in my case, inside the trunk of my Sebring convertible or on the roof rack of our Expedition). The Sebring carries the antenna on the left rear deck, using a home-brew stainless steel mount. The Expedition flies the antenna on the roof rack, again on the left side, and also using a home-brew mount that employs a commercial mount as one element, two stainless steel u-bolts, stainless washers and nuts, and stainless anti-vibration nuts as the "shake-loose-stopper".