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Is anyone here using a W3EDP antenna?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KC3RN, Nov 20, 2018.

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  1. KC3RN

    KC3RN Ham Member QRZ Page

    So I hung a homebrew W3EDP antenna over the last weekend. It actually seems to be performing pretty well. The specs call for 450 ohm window line, but I used 300 ohm twin lead instead, as that's what I had on hand. I'm using an LDG 4:1 balun at the feed point. The internal tuner in my IC-746 is able to find a match on everything except 160m. I have an "ugly" balun/choke at the feed point, which seems to do a pretty good job of keeping RF off the feedline and out of the shack.

    The specs I've seen recommend a current balun on the feed point. The LDG is a voltage balun. So my question is can expect any performance improvement by switching out the voltage balun for a current balun?
     
  2. NH7RO

    NH7RO Ham Member QRZ Page

    Not unless you experience RFI/common-mode troubles.
     
    K7TRF likes this.
  3. WA7ARK

    WA7ARK Ham Member QRZ Page

    How long is the feedline?
     
  4. KC3RN

    KC3RN Ham Member QRZ Page

    125 feet. RG-8X.
     
  5. KA2RRK

    KA2RRK Platinum Subscriber Platinum Subscriber QRZ Page

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    KA2RRK
     
  6. W6JJZ

    W6JJZ Premium Subscriber QRZ Page

    At the risk of being a little irrelevant, I'm puzzled.

    First some background: I've always thought of the W3EPD antenna more or less as it was originally described by W3EDP's friend Yardley Beers, W3AWH, in QST in March 1936. That was an 84 foot wire with a 17 foot "counterpoise" (although on 20 meters W3EDP used a 6.5 foot counterpoise, and on 80 and 10, no counterpoise). W3EDP fed the two sides of his EDP from a parallel-tuned circuit in the transmitter, but later versions have usually substituted a balanced tuner or a single-ended tuner plus balun. Also, along with usually a 17 foot counterpoise, later iterations have sometimes used an 85 foot wire in place of the 84 footer.

    So here's what puzzles me: It’s true that we can think of W3EDP's EDP as similar to an end-fed Zepp with a 67 foot radiator and 17 foot feedline, but with the feedline pulled apart, so it’s no longer a feedline. But what's the configuration of a W3EDP antenna that actually incorporates either 300 or 450 ohm feedline (or some other impedance line)? Is it a 67 (or 68) foot radiator, with 17 feet of balanced feedline (maybe adjusted for velocity factor)? Isn't that simply an end-fed Zepp? Or is it an off-center fed wire, 84 (or 85) feet on one side and 17 feet on the other side of the feed point, and fed with balanced line? I have a hard time seeing that as a W3EDP, either, and it would be odd otherwise. And then, apparently, after the balanced line (whatever its length), there's a transition to coax. Still odder. What's the reason?

    I guess I'm asking for a lesson in antenna evolution. How did the W3EDP antenna (which I’ve used) morph into something with the same name using feedline (balanced and coaxial)? And what does it look like?

    Charlie, W6JJZ
     
  7. KC3RN

    KC3RN Ham Member QRZ Page

    Charlie, here's what it looks like:
    upload_2018-11-20_21-46-38.jpeg

    Mine runs vertical for the first 40 feet, then horizontal for the remainder.
     
  8. W6JJZ

    W6JJZ Premium Subscriber QRZ Page

    That's what I would call an end-fed Zepp. Also, the impedance at the bottom of the ladder line will vary considerably, depending on band. You may have considerable loss in the coax.

    Charlie, W6JJZ
     
  9. KF7WMM

    KF7WMM Ham Member QRZ Page

    I have used one awhile back for about one year...Home made open line feed,Dimensions by the book as your pic..17' X 67' for an 84' radiator..About 25' vertical,rest sloped to roof peak..I started with a 4:1 currant balun,switched to a balun design 9:1 Unun..A lot of counterpoise wires,maybe three feet above ground..It worked well for an HOA home..Upper part of 20 meters was touchy,used an LDG 100 pro 11 tuner at that time..I had better luck with the Unun but I think a 4:1 Unun may be better..Need to adjust counterpoise lengths for best tune..I tried 1/4 wave 80 thru 10..Still had to tinker a bit especially on 20..Antenna Nazis made me remove it..Best compromise antenna I had was a 124' end fed and 9:1 unun..I now use a Zero five 27' vertical with 70 radials..Works for me but am going to put up a 72' end fed and 9:1 for NVIS..I had 75' of RG 213 on the W3EDP..No choke,no RF in shack..Bob/KF7WMM
     
  10. KF4ZGZ

    KF4ZGZ Ham Member QRZ Page

    Looks like a bent 30m j-pole to me. ( the KC3RN pic)


    Matt
     

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