You can just fit 17 turns of RG-58 on a FT240-31 toroid, and that will
give you over 8000 Ohms CM impedance on 160m
Steve G3TXQ
On 20/10/2012 16:56, Jim Lux wrote:
On 10/20/12 8:47 AM, Cqtestk4xs@aol.com wrote:
Along with that line of thinking...using RG58 on a 4 inch core.
About how
many turns? My thinking is around 25 or so.
why not 4 or 5 turns on a 2.4" ferrite/powdered metal core? 4" PVC
core is a foot per turn, 25 turns is 25 feet of coax (which I grant
you probably already have), but say it's 0.25/ft. that's 5-6 bucks
worth of coax against a $5 ferrite core, which will be more broadband,
higher choking impedance, physically smaller, etc. Air core chokes
don't have a lot of resistive impedance: you're depending on their
inductive reactance, and that's subject to cancellation from parasitic
C, etc.
You'd have to check K9YCs writeup to see what an appropriate material
for the core would be. #31 is the sort of general go-to material for
ham band use, but there might be something better for lower frequencies.
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