This is just a few things I've noticed in this thread.
If you have the choice, a 'hard-mount' is better than a mag-mount. That pertains mostly to performance but also in 'practical' aspects. There are a number of reasons why a hard-mount isn't practical or desirable, but a mag-mount is always a compromise.
One aspect of feed line choice that isn't always taken into account is the length of that feed line's run. For most mobile instalations the length isn't a determining factor, it's just not long enough to make any practical difference in losses. RG-58 of a good quality is adequate in most cases. The key in that is that 'good quality' thingy! Most RG-58 that's commonly found just isn't the 'best' in the world. Didn't used to be that way, but it is now. Nothing wrong with using RG-8x (of good quality). The biggest thingy with it is that it's a little larger than RG-58, requires different size reducers. Again, the usual length of the run isn't going to make any prectical difference in losses. Fractional dB losses mean nothing, you can't 'hear' them and no one else will either. The Times Microwave LMR-200 is the equivalent of RG-58. LMR-240 is the equivalent of RG-8X. Nothing especially beneficial about them, any loss difference is negligable at HF.
The key to any antenna installation is in the tuning the antenna part. No antenna can be 'pre-tuned' exactly, or even 'well' in most cases. There are always two steps in tuning an antenna. One is making the thing resonant and the other is matching the antenna's input impedance to the rest of the system (SWR). The first step is almost never done and that's the most important one. The second step, matching impedances (SWR) only affects how much signal get's to the antenna, NOT how well the antenna radiates it. It's a terrible way to 'tune' an antenna. The big deal about resonance is that resonance means that the reactances in the antenna are neutralized, nulled. So?? Reactances don't radiate anything, or contribute to the radiation of anything. "But everybody does it that way!", yeah right...
- 'Doc