The mains borne noise floor seems to follow a comb filter pattern, quieter on MW commercial and amateur bands but very noisy in-between, (including the CB frequencies!) I think this is due to the power companies doing their best to reduce noise for those that complainants loudest but realised only a few days ago that I'd been short wave listening on the 11m inverted dipole! Going back to an 80m transmission I could tell no difference in signal between the array and the v proving the point that a 'long' bit of wire high up is still holds true I recently had someone put up an inverted v dipole for CB transmission and added an antenna switch so I could easily changeover for SWL. You can also rotate the loop and null out local interference but it was definitely down on signal compared to the fan array. I experimented with a homebrew magnetic loop and although it adds another tuning control it's amazing how well it works for such a small antenna. It's only recently that I've played around with alternatives. It worked well and after 20 years it's still up. To get round this somewhat I made a fan dipole array with each dipole tuned to my main bands of interest, (80m, 40m, 20m & 10m), and thought I'd built the ultimate antenna. This still holds true but I have noticed the noise floor increasing, (modern electronic equipment RFI), as well as mains borne noise. In the 'old' days it was just a case of slinging up the longest bit of wire as high as you can and that would do the job.

I can only give you my personal experience of SWL man and boy. You'll probably get as many different suggestions for SWL antennas as you do CB antennas

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