I recently build a Loop antenna for CB radio, or at least i tried.

Its made out of a 80cm diameter Loop of RG58 Coax (shield and core connected at the ends), a Coax stub condensator and a unshielded wire primary loop.

When i put my SDR on it, it seams to have way to much of a wide reception (calculator said it would have only like 40-50khz wide reception band).

When i put my analog power/swr meter on it, it claims to have a SWR of 1.2 and takes about 3.5W of power (compared to my dipole taking 4W).

But when i put the NanoVNA on it to get a more accurate reading of SWR, all i see is a flat line that claims a SWR of about 50.

When i pump up the stimulus frequency up to 300+Mhz i get some SWR dips there down to 1.6, but i assume thats just the Primary loop resonating.

Any idea why i get results on my analog SWR meter but not on the NanoVNA? Is the NanoVNA maybe putting to few power into the loop to make it resonate?