End Fed Zepp Antenna

Discussion in 'General Technical Questions and Answers' started by W8RID, Jul 21, 2002.

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  1. W8RID

    W8RID Premium Subscriber QRZ Page

    I am new to this hobby. I've been a Technicin for about a year and a half now.

    I'm not doing much talking but a lot of listening. I'm starting to get into some local nets.

    My dad is a General. He has been doing this for ever.

    I am trying to get plans or a program that will show me how to make a End Fed Zepp antenna for any frequency.

    I need to do the end feed due to the configuration of my yard. A center fed would not be feesable.

    Does anyone know of a way to do this??

    Thanks

    Bob
    W8RID

    [​IMG]
     
  2. W9GB

    W9GB Ham Member QRZ Page

    Bob -

    The End-Fed Halfwave Antenna is nothing more then a resonant dipole antenna that is fed at the high voltage point (high impedance end) instead of in the center, which would be high current point (low impedance). This antenna is as old as radio and is probably best known as the Zepp Antenna named after the airship is was commonly used on, Zeppelin. Since in the early days of radio the wavelengths used were very long the antennas were also long. An end-fed antenna that could be trailed behind the airship was much easier to implement then a center-fed dipole or a 1/4 wavelength antenna that required and extensive ground plane to function properly. Amateur radio operators had found that when cut as a 1/2 wavelength on the lowest frequency of operation it would still load as a voltage fed antenna at all harmonic related frequencies and it was often more convenient to feed the antenna at its end rather then in the center.

    Here are some links about the End-Fed Zeppelin antenna:

    I like K5CNF's graphics !
    http://www.antennex.com/hws/ws0800/dbl_jp.htm

    http://aa5tb.home.texas.net/efha.html

    http://www.sadona.com/news/ant_dblzepp.html

    http://www.cebik.com

    http://www.qth.com/dwm/signal-trap.htm

    http://kk4tr.tripod.com/index-10.html

    http://members.fortunecity.com/xe1bef/hf-antennas.htm

    73 de w9gb
     
  3. KE7VE

    KE7VE Banned QRZ Page

    Bob,
    I know what your going through.I have been looking for info on how to raise various fruit crops and get tons of stuff on what I don't want instead of an answer to some very basic questions. My real problem, I think, is I don't know enough to phase the question properly.

    You can find the info on the end feed zepp in the ARRL antenna Handbook...it will explain all but to run this you need to make an antenna tuner which will go from unbalanced coax to balanced line. You can buy an antenna tuner which "claims " to do this, it uses a ferite balun, BUT it will not work at high SWR. Which is really what you want if you are looking to operate on several frequencies.

    An easier way to go might be with an end feed wire, which you can use a simple L network with. Just a coil and cap, very easy, simple to adjust, and very efficient if the set up is right.

    To really help you I need to know some stuff. What is the physical layout like....are you in a basement....on the second floor...how long a run of wire can you make.....how high.... do you have a good ground nearby?

    Antennas are often a comprimise based on what you can do. Much of that depends on all the possible layouts and kinds of antennas we could make work at your location. For what we have given, your physical layout and what freq etc you wish to work, we can find a "best comprimise" antenna, but we really need to look at the physical layout and what you want. I understand that you may not know exactly what you want since you are new to this, but you main limitation is your lot with trees etc and what you can spend. What I trying to say here is that I love these 3D real world problems and after 39+ years on the air and reading many antenna handbooks 1000 times I believe I can really help you out but I need more info on you physical layout and ideas about what you might be interested in.

    See if you can describe your lot, and what you might like to do on HF and I'll come up with suggestions and what you need to know to get it done.

    73 Marty K7RKR AMI#20
     
  4. K9STH

    K9STH Ham Member Volunteer Moderator QRZ Page

    One thing about the Zepp is that it works well on frequencies that are powers of 2. For example, a Zepp about 260 - 270 feet long works on 160, 80, 40, 20, and 10 meters. However, it does not work well at all on 15.

    270 feet represents a half-wave on 160, full wave on 80, two waves on 40, four waves on 20, and 8 waves on 10. The 6 wave length that happens on 15 doesn't work very well at all. As the frequency increases, the antenna actually starts exhibiting some gain.

    It doesn't have to run in a straight line to work (most wire antennas don't have to run in a straight line as well). The best wire antenna that I ever had was a 270 foot long Zepp that ran from my parent's house (on one corner of a very large lot - 200 feet X 160 feet). It started at the house, ran to a 30 foot "T" mast in the yard, then up about 40 feet to a wild cherry tree, and then at an angle back to a 20 foot telephone pole in the back yard. I unwound some old TV power transformers to get enough wire to put this thing together (I was 15 at the time). Put it up at 3:00 AM, in about 3 feet of snow, during a severe snow-storm! The things we do when we are young!

    I feed it directly into my Heath DX-100 since the Pi-network on it would match from about 20 ohms to over 600 ohms. Fed it with 300 ohm transmitting twin-lead. If you use 300 ohm line, then a simple balun like the old Heath B-1 will work if you need to match to coax. If you use a fixed 4:1 balun, then you might seriously consider using 75 ohm TV type coax to the rig. The rig (even with the fixed output like many of the solid-state rigs) will work fine with 75 ohm coax. For powers up to about 200 watts output, the "normal" cheap TV 300 twin lead will work. For powers up to around 1 KW, the foam filled 300 ohm twin lead will handle the power.

    I have up a 67 foot long Zepp right now that feeds into my AM shack. It is fed with 300 ohm foam filled twin lead. Although it is very low (only about 10 feet off of the ground), it works well as a "cloud warmer" for close-in contacts. This is for 80, 40, 20, and 10. Since these transmitters have a wide range Pi-network, I feed the 300 ohm twin lead directly into them.

    Glen, K9STH
     
    W1SRR likes this.
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