I have always wondered ......... since I have acquired six of those
square snap on ferrite blocks if they would provide any sufficient
chocking action on my 12 meter or 6 meter beam coax feeds as the fit
perfectly on LMR 400 or 9913? If they are of any value what would be
the recommended spacing on the coax starting at the feed point?
Herb Schoenbohm, KV4FZ
On 12/3/2014 10:50 PM, Kim Elmore wrote:
For the purpose of a choke, I used a couple of 2.4" OD ferrite toroid cores
stacked as a choke-type balun for an OCFD (a Force 12 Sigma 80). I wound about 20
bifilar turns of 16 ga enameled wire on the stacked cores It seems to work, at
least at 80 m. I made a similar one for an inverted V with the center up about 40'.
I assumed this works like a choke-type balun. Am I correct?
Kim N5OP
"People that make music together cannot be enemies, at least as long as the music
lasts." -- Paul Hindemith
On Dec 3, 2014, at 17:55, Jim Brown <jim@audiosystemsgroup.com> wrote:
On Wed,12/3/2014 3:31 PM, Roger (K8RI) on TT wrote:
Take for instance the 75 meter, center fed dipole whose impedance can vary
widely from well below 50 ohms to above 50 ohms depending on height. You are
feeding a supposedly balanced antenna with unbalanced line. (Good place for a
choke).
And it also varies widely from one end of the band to the other. We can see
this on a Smith Chart and on an SWR curve beginning around slide #30. This
particular dipole is modeled around 100 ft over average ground, and Z at
resonance is 76.5 ohms. Over lousy ground, the Z would be in the mid- to
high-80s of ohms.
http://k9yc.com/PacificonSmithChart.pdf
73, Jim K9YC
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