Darrell asked: So how would the Elecraft BL1 Balun do with the End-Fed Zepp? Depending on the ground losses, the impedance could be 5000 ohms or so. Would the 4:1 transformation ratio still hold true? What would the efficiency of the balun
be? Would 100 watts from a K2/100 cause saturation of the balun core? ------------------------------------------------ Dipole = 1/2 wavelength radiator. Zepp = dipole radiator fed at one end with 1/4 wavelength of open wire feed line. The 1/4 wavelength feed line converts that high impedance to a low impedance at the rig end. That's why the balance in such an antenna is not bad even though one side of the open wire line connects to the end of the dipole radiator and the other side connects to nothing at all. Very little current flows into the end of the dipole and very little current flows from the end of the unconnected feeder (some current flows due to losses in the insulators at the end). Such an antenna is a "piece of cake" for a balun and you may find the feeder currents are equal even without one. After all, that arrangement is simply a 3/4 wavelength long wire connected to the "hot" side of the rig output and a 1/4 wave "counterpoise" connected to the other side, only the counterpoise and the first 1/4 wavelength of the radiator run in parallel to minimize radiation (that was important in Zeppelins where they were used). Many Hams try to use lengths other than 1/2 wave for the radiator and 1/4 wave for the feeders. When you do that, all bets are off. It's like any "non-resonant" doublet or end-fed wire. They can work well, but you must have a matching network that can handle some potentially extreme impedances. Actually at any but the exact lengths for a proper Zepp, the feeder will radiate as much as the antenna. That's why non-resonant antennas fed with open wire line are usually center fed (so-called doublets). Such center fed arrangements hold decent balance regardless of frequency. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
