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![]() "Craig Buck" wrote Two big advantages of the center top feed as opposed to bottom end feed is center top requires no radials. Bottom L will need a minimum of 8 100 foot radials in your application and some would argue you need many more than 8. Have fun burying 800+ feet of wire. Second, top feed gets the high current radiating part of the antenna up higher. Check out http://www.cebik.com/ltv.html and his discussion of ladder line at http://www.cebik.com/gup/gup32.html. He concludes a 1:1 balun is best. If you have 37 feet of height you can feed at the top and run the wire straight down, back up and then down again for a total of 3x37= 111 feet of wire on the vertical side. On the horizontal just bend back at the end or let the end drop down vertically. Sure it will have narrower bandwidth than a straight dipole but you have a tuner and you can't have a straight dipole. -- Hi Craig, Mr. Cebik says nothing about wrapping radiators back and forth near each other as the earlier referenced url: http://hamgate.sunyerie.edu/~larc/su...inverted_v.htm Cebik does comment: "Bending the horizontal arm far end down: If horizontal space is limited, a common practice is to bend (or dangle) the outer ends of a dipole downward. since the region is the high voltage and low current portion of the antenna, the radiation pattern is least affected by modifying the geometry." -and- "Like many wire antennas, the inverted-L will tolerate moderate alterations of geometry to fit the space available and still yield good, if not peak, performance." each leg longer. According to Cebik if you can get 3/8s wavelength, you are very close to the full performance of a half wave. Feeding at the top middle does not require a radial field to work. It doesn't appear that Cebik intended to imply that 3/8~ off-center feed would ever approach true1/2~ dipole performance, just that it would still operate. These off-center-fed variations (of Carolina Windhams?) are confusing, no matter how much wire they use. Remember I don't need an all-band compromising performer like the T2FD or Windham, but a specific performer on 2182 Khz, and hopefully at least through 4125 Khz. Doing this with 70' of horizontal span and two vertical attachment points about 37' high is the challenge I am asking for help with. I cannot run anything like KGØZP does, which creates (in his location) a near-field coupling nightmare, in my opinion. Your suggestion (doubling the verticals), which varies from both the KGØZP design and Cebik's "moderate geomtery alterations", would at least add electrical length, but it remains off-center-fed and therefore never creates a 1/2~ dipole, correct? If I stuck with a 1/4~ end-fed L, and only used 8 radials of 20-40', could this still outperform an off-center-fed antenna off any length on 2182 Khz? Thanks again for the comments and ideas, Jack painter Virginia Beach VA |
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