Marconi,
I don't remember if you used an antenna analyzer in your testing or not, I am sure you used a field strength meter (memory isn't totally shot anyway). Those analyzers really do tell you much more than any SWR meter can. As in any reactance present and if it's inductive or capacitive. That sort of measurement can lead you in the direction you should go to make an antenna 'better'.
If you do have an analyzer you can 'play' with antennas and learn quite a bit. One of the things you learn about any 1/4 wave length antenna is that even at resonance, the input impedance, zero reactances, the resistive part of that impedance isn't going to ever be 50 ohms unless you 'play' with the shape of the 'other' half of the antenna, the groundplane. If you tilt those radials down from horizontal, at some point you ~can~ reach a near 50 ohm input impedance. When a vehicle body takes the place of those radials things get very "iffy" because it's very difficult to change the 'shape' or 'dangle' of that vehicle body. Unless you are very, very lucky, it just isn't going to happen. That means that you have to either match the resulting antenna input's impedance to the rest of the system, or settle for a little bit of reactance figuring into the thingy and getting near enough to 50 ohms impedance (it's NOT totally resistive though) for the radio to 'like' it. That's typically what happens when only using an SWR meter, since it doesn't know, nor is able to tell you anything about the reactances present. The more reactance present the less resonant the antenna, BUT it will usually work satisfactorily, even if it isn't exactly resonant.
With a mobile antenna, especially a 1/4 wave at 11 meters, it's easier to 'juggle' the antenna's length to change the antenna's reactance than to 'juggle' the groundplane. That's true of any mobile antenna not just a 1/4 wave, loaded or not. The 'other' easy way to handle the reactances present (if any), or to match the impedance of the rest of the system is by the use of an impedance transformer to change the antenna's 'not 50 ohms' impednace to a 50 ohm impedance. Bunch of ways to do that, none really difficult, just not very common. There's a phobia associated with those impedance matching transformer devices, otherwise known as a tuner, that most people seem to have. If done correctly though, there's less loss associated with a tuner than there will be with un-dealt with reactances (impedance mismatches).
There's absolutely nothing 'new' in any of the above. And more than likely most people already know it, or have heard it before.
- 'Doc
PS - Marconi, don't drop the other topic!
