How to make an end fed dipole?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KJ6CEA, Nov 20, 2010.

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  1. KJ6CEA

    KJ6CEA Guest

    I was thinking, Im getting set up for a camping station. While I will have a dipole, It sure would be nice to have a antenna when I have only on support. Is there a way to make one easily? I have some 50 Ohm coax and 16 guage wire. Is there an easy way to make one with parts from radio shack only?
    I would like to have 100watts but 50 would be bearable. Im fine with a counterpoise system also.
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Dipole = two wires ("di") pole.

    No such thing as an end fed dipole. You can have an end-fed half wave antenna that works like a dipole, though.

    For a single band, use 1/4 wavelength of open wire or ladder line to feed it, and it becomes an "end fed Zepp," which can work pretty well.

    If you have one single elevated support for an antenna, a real dipole (center fed) installed as an inverted vee is less fussy.
  3. VK1OD

    VK1OD Ham Member QRZ Page


    An alternate definition is that a dipole is two opposite charges, in which case and end fed dipole is not inconsistent.

    However, I have to answer the OP's question with a question. Why does the physical configuration (only one elevated support) mandate end feeding?

    You could centre feed a sloping dipole, or centre feed an inverted V.

  4. W0IS

    W0IS Ham Member QRZ Page

    Yes, if it's fed at the end, then by definition it's not a dipole.

    There are two easy antennas you can make, however. The first is what 'WIK suggests, and make an inverted vee. Put the center of the dipole on your support, and run the two ends to any available location. That can be the ground--just use a tent stake or something to secure it.

    Another easy antenna is a quarter wave wire, which is best if it's more or less vertical. But it need not run straight up and down. A 45 degree angle, or even shallower, will probably work fine.

    There are two ways you can do that. One is to run your coax to a convenient point on the ground and go up from there. For an even easier setup, you can simply run the wire directly to the center pin of your rig's coax connector. A "banana plug" is helpful for doing this. This will work better with a lower power level. It works great for QRP. With higher power, you'll have a lot of RF floating around the rig, which might possibly cause problems. On higher frequencies and/or higher power, it might also cause RF exposure issues. Right off the top of my head, I would say that 50 watts on 20 meters won't cause any such issues (but you should check it yourself, since you are then one foot away from the antenna).

    With the quarter-wave wire, you do need as good a ground as possible. Wherever the wire starts, the ground should be attached at that point. Since you probably don't have ground rods with you, just run any available wire along the ground. Multiple radials is even better. Attach these radials to the braid of the coax. Or, if you plug directly into the rig, attach them to some convenient bolt on the chasis of the radio.
  5. W5DXP

    W5DXP Ham Member QRZ Page

    Just a nit from The IEEE Dictionary: "dipole antenna - any one of a class of antennas having a radiation pattern approximating that of an elementary electric dipole." Nothing said about the conductor being broken in the middle.

    As Owen implies, the word "dipole" does not refer to two physical fishin'-type poles. :) It refers to the two (and only two) electric (voltage) poles at each end of a dipole.

    Hint: a gamma-matched 1/2WL single element is still a dipole. The single element directors and reflectors on a Yagi antenna are dipoles. An end-fed Zepp antenna is a dipole.

    The professional definition of "dipole antenna" certainly includes 1/2WL end-fed dipoles. It is the colloquial ham lingo use of "dipole antenna" that is different from the professional definition. I vote for the IEEE definition.
  6. KB4QAA

    KB4QAA XML Subscriber QRZ Page

    AA5TB has a nice discussion of end fed antennas with recommendations for construction. I haven't tried his plan yet.

    Why would someone desire an end fed antenna? Simplicity of deployment, e.g. throwing over a tree limb, dropping out an apartment window. We apartment dwellers can get pretty desperate!! ;)
  7. VK1OD

    VK1OD Ham Member QRZ Page


    I think you are quite right, except that votes don't determine facts... a concept a bit alien to ham online fora! Voting often shows some misconceptions to be very popular, perhaps even mythical.

    The misleading things about most "end fed half wave dipoles" is that the description ignores the path for current at the feedpoint other than that on the dipole conductor. Many of the configurations are three quarter waves, fed one quarter wave from one end, eg J Pole, the common End Fed Zepp.

    It is the acceleration of charge from one side of the dipole to the other that gives it its radiation characteristic, even if it is a lot less than a half wave in length (the latter causes difficulty with a lot of hams who insist that a dipole by definition is a half wave in length).

    To the OP, needing to connect one side of your feedline to dirt introduces a variable and almost always lossy element to the system. The concept that you can lay a "wire counterpoise, tuned or not' on soil doesn't fully address the problem as the fields due to current in that wire will heat the soil more than if they were not in such close proximity.

  8. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    The disadvantage of unbalanced antennas is they typically create all sorts of problems with RF induced into the equipment. Of course, that can also happen with a balanced antenna that's simply "too close" to the equipment, or balanced antennas fed with unbalanced feedlines, without baluns.

    Lots of bugaboos are possible, but end-fed ones seem to introduce more of them.
  9. N5YPJ

    N5YPJ QRZ Moderator QRZ Page

    I know that you mentioned coax fed end fed wire, there is an end fed half wave wire that is fed with ladder line. Trouble is in certain situations the feed line is very susceptible to radiating and picking up lots of noise. I used to think that they were panacea but more trouble than they are worth many times.

    If you absolutely have to have an end fed half wave with coax feed then I suppose, controversies aside, the easiest would be the J - Pole.
    Last edited: Nov 20, 2010
  10. KJ6CEA

    KJ6CEA Guest

    Ok guys:

    Dipole configurations:
    I thought you guys might bring it up, Yes I can and plan to include this in my go kit, but if it is short term Im not really interested in throwing up a rope, pulling up the wire, staking it down and the other end.

    Say for 20m how would I make it?
    Coax taking off the shield leaving the coax and insulated weight? What should I do to the shield? Should I roll up the coax a couple of times? Im looking to be able to work (almost) every station I hear, so no perfect rx.

    I guess im realy not going to run 100watts or even 50 continually, but if im in the middle of a qso I would like to know that I can turn it up if conditions get a little worse.
  11. AD0KI

    AD0KI Ham Member QRZ Page

  12. KJ6CEA

    KJ6CEA Guest

    Thank you!

    Everyone else, Im looking for application not theory. I don't care how it works I just want it to:D
  13. K1DNR

    K1DNR XML Subscriber QRZ Page

    If you aren't looking for a theoretical explanation, I can help you.

    Keep it simple.

    You can't get more simple than a dipole in many ways.

    For 20 meters, with one support, do this:

    Cut two pieces of wire approximately 17' long. You will need to trim them a bit. Cut long to be on the safe side.

    Connect the shield to one wire, connect the center to the other. This is a dipole with no balun. Don't worry about the balun at this point, and don't randomly coil up coax. Unless it specifically matches up with your operating frequency, it may do more harm than good.

    If you can get the end of one leg up 30', you will come out horizontally approximately 14 feet to the point it meets the ground. Put an insulator on the end (this can be anything from a plastic coke bottle to a "real" dog bone insulator). cut a hole - insert wire - tie it off. In the other end, cut a hole, put a piece of nylon string or fishing line, and tie it off to a branch or stake in the ground.

    That's a 20m sloper.

    For an Inverted Vee, put the middle up 30', and bring the ends down - they won't reach the ground, so extend with fishing line or nylon rope. Use an insulator of some kind - coke bottle, pvc pipe, CD jewel case, plastic tampon dispenser, what ever :)

    That's a simple and cheap 20m portable antenna.

    If you want to improve on the situation, add a small MFJ tuner with the built in balun, get some ladder line or TV twin lead, and feed your dipole that way.

    My portable setup for HF = 31' fiberglass pole, dipole cut for 40m (66' or so), 50' TV twinlead, small MFJ tuner with balun. I can work 40m through 10m with that set up.

    30' is a bit low in height for 40, but you'll make contacts if the band is decent.

    I've used that portable setup in an inverted V configuration and worked Europe and South America from the US Midwest with no problem at all on 40, 30 and 20 meters.

    This is not a set up to run high power (I was running 100 watts)

    You won't be the strongest station.

    But it works. You'll make contacts and have a lot of fun. Its also light and easy to carry.

    Omit the pole and bring along some baseballs to launch your wire in the trees...
  14. KJ6CEA

    KJ6CEA Guest

    Thanks, I understand a dipole.

    I am looking for how to make a quick end fed **antenna**, NOT a dipole, thanks though.
  15. K1DNR

    K1DNR XML Subscriber QRZ Page

    A dipole is an antenna :)

    I'm not sure I understand the fixation on end-feed...

    I'd understand a desire to experiment - but you said you weren't interested in theory :confused:

    You are over complicating things and you'll probably have worse performance than you will have keeping it "simple".

    Just my adivce... Been a ham since I was 12. Made every mistake one can make...
  16. KJ6CEA

    KJ6CEA Guest

    Haha I like to see it, If I can build it then I can go over the theory to see what is going on. I learn that way better
  17. K1DNR

    K1DNR XML Subscriber QRZ Page

    Good luck with it. I read the WorldRadio article. It would appear to me that it isn't so much an "end fed dipole" as it is a dipole that uses the coax braid as the other leg - hence the 1/4 wave length of coax and placement of the choke.
  18. AL7N

    AL7N Ham Member QRZ Page

    "end fed" dipole....

    Get some suitable coax that is long enough and skin the outer jacket off
    1/4 wavelength of it. Then bunch and pull the shield braid back down
    over the coax away from the skinned center conductor for about 1/4 wavelength. The rest of the coax can be "any' length, but the connector that hooks to your radio should be at least 1/4 wavelength or more from where the end of the shield braid is.

    Now you have a half wave dipole fed at the center, but the feedline goes up inside one end of it.

    Put a suitable hook or something on the far end of the skinned center conductor to hook a rope to and haul the thing up in the air either vertically or sloping half horizontally and get to work.
  19. KJ6CEA

    KJ6CEA Guest

    I will have to try this. It looks good, at least to try.
  20. PD7MAA

    PD7MAA Ham Member QRZ Page

    1/2 wave endfed 20m.

    This antenna has brought me lots of contacts all over the world.
    Easy to construct.
    The coaxversion with stub is verry lossy......
    Have fun .

    73 John
    Last edited: Nov 20, 2010
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