Re: Extending the range of a Discone antenna down to 3.6 MHz
It does not tell you anything about it's performance.
Very sorry, but because an impedance is high doesn't mean anything.
Reception antenna's often have terrible bad SWR, doesn't mean anything.
For transmitters it's a different story as amplifiers or cables could burn when not being 50 Ohm and/or matched.
For example, I use the G5RV, often regarded as a poor antenna because the SWR can be very high, so some folks with analysers started to "improve" it.
Result, ZS6BKW, sure it has a better SWR but the performance is far worse, they only focussed on SWR alone.
I personally do not care about SWR, I have tuner to solve that for TX....for RX it matters little.
Google for: "Reflections" By M. Walter Maxwell
Not only a very good read (very funny too) but also proven reality about antenna's and transmission-lines as also described in: ARRL Handbook and the Antenna Book.
SWR isn't as bad as most people think