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Balun question
Highland Ham wrote:
I have corrected the attribution marks below. Wonder what newsreader you are using? Highland Ham wrote: So it makes no sense to connect an OCF Dipole directly to a twin feeder . Cecil Moore wrote: So exactly to what feedline does it make sense to connect an OCF Dipole? ======================================== To coax via a (voltage)balun (usually 4:1 ) The balun being either a ferrite bar or a toroid , wound with 1 bi-filar winding eg a 2 to 1 (auto)transformer resulting in 4:1 impedance transformation. A 4:1 voltage-balun balances the voltages so with unequal impedances looking in each direction at the feedpoint, the currents will be unbalanced causing feedline radiation. That's why the Carolina "Windom" (sic) has a choke some distance down from the feedpoint. So an OCF Dipole seems to have feedline radiation with either twinlead or coax+voltage-balun. The ARRL Antenna Book says a 4:1 current-choke-balun will solve the feedline radiation problem but 4:1 current baluns usually require two cores. -- 73, Cecil http://www.w5dxp.com |
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