After all the effort you put into building that loop, does it make sense to shave a few yen on spliced coax, when you know it will likely introduce unnecessary loss?
Mostly, I'm curious about if a "properly" done coax extension will exhibit the same measurable loss as compared to my current improperly done coax extension.
But you're right. With all the careful work balancing the alternatives and finding a feasible, minimum-loss construction technique for the antenna, it makes more sense to buy a new unbroken coax run and to know that transmission line losses are minimized.
For my QRP situation avoiding loss is critical, but in general, are coax runs for HF ham work almost always continuous and unbroken? Or are there any rules of thumb for how to extend already-installed lengths of coax cable?
Actually if I'm buying new coax anyway, maybe it's time to think about the type of coax and the inherent loss in the coax. I think I now have RG58A/U, which if I recall correctly is a shade lossier than RG58/U. I'll have to look to see what types my dealers stock, but what would be a good low-loss HF/VHF coax type for a cable length of 15m?
Transmission line theory is a rather foggy subject in my mind, but I look forward to learning more.