Looking for #AmateurRadio antenna feedline common-mode choke advice.
I'm currently running a 40m EFHW for 40m, 20m, 15m, and 10m, and my noise floor is high, especially north of 40m. Someone in my local club suggested 25' of coax wrapped around a 4" PVC pipe, but http://www.karinya.net/g3txq/chokes/ makes it look like air core CM chokes are fairly narrow bandwidth and high in reactive impedance, so not obviously best for a single EFHW working those bands.
It looks like a line of 10 FB-31-1020 ferrites would give me >1k primarily resistive impedance over that swath of the HF spectrum, and so be a good match for the antenna I'm using.
Any #HamRadio folks have thoughts on that? Am I crazy? Do I misunderstand? I'm just a baby ham...