Hi Michael,
As others have suggested, I wrap 10 to 14 turns of coax through an FT240-31 toroid core (based on work done by K9YC) and I locate this choke approximately 0.05 wavelengths (on the lowest band) from the feedpoint of the EFHW (based on work done by AA5TB which I also confirmed via modeling).? Doing this does a great job keeping RF off the outside of the coax shield between the choke and the radio.? Also the outside of the shield between the feedpoint and the choke acts as an adequate counterpoise so you don't need to install an additional counterpoise wire.? The choke also helps reduce common mode noise that travels from your shack up to the feedpoint via the outside of the coax shield and this therefore often helps reduce your receive noise floor.? It also makes the SWR much more stable (repeatable) as it eliminates the outside of the shield between the choke and your radio from being another variable (additional counterpoise) that would otherwise alter the SWR depending on how it's coiled up, what its touching, etc.
73,
Don (wd8dsb)?
