Anything above 2.0 I would think the antenna was stepping into 'bad matching' territory, maybe I'm being overly conservative, I'm not sure.

I am not an expert with all of this but I consider an SWR of 2.0 or less to be 'good' and 1.5 or less to be 'very good'. I have been using my loop for about a year now and in my limited 'year' experience with receiving SW with the loop I thought it had been doing well. The SWR and Impedance was bad to terrible on all frequencies and some parts it was horrendous (see the attached screenshot). The surprise came when I hooked up my Wellbrook loop antenna and did a sweep from 0.1 MHz to 30 MHz. As I expected, my Diamond discone and Siro UHF discone do better on some frequency ranges and a little worse on others.

I have never used one before so I have been playing with mine for the last hour or so, just seeing what I am getting as far as SWR and Impedance goes on my three SDR/scanner antennas. I finally got one of those NanoVNA's people have been talking about.

V2 plus4