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
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|