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?
I love the word Mantelwellensperre, peak german language :D
I build a Air-Core choke from a part of feed line right below the antenna now, and got some slight improvements.
I will try to improve the feeding loop position to see if it gets the swr down a bit more. By now i am already quite happy with the antenna, during a test i managed to make a ~15km Thor8 connection while the antenna was still inside the house (with 4W AM Tx and the receiver in SSB/USB).