Balun 9:1 Unun End Fed Antenna Questions

Discussion in 'Ham Radio Discussions' started by W9MMM, Apr 26, 2019.

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  1. W9MMM

    W9MMM Ham Member QRZ Page

    Hi Everyone,

    This is my first post on QRZ. Great to see all the discussions out there. I'm setting up a Balun 9:1 Unun End Fed Antenna. I have a large property with acreage. I'm using a Balun Designs 9:1 Unun and I'm planning to setup a 175 foot wire which is the max magic number in the manual for the unun. My feed line is 150 ft of LMR-400. It will hopefully be up around 75ft from trees end to end with ceramic insulators. A 1:1 isolation/choke balun will be at the transmitter side of the feedline. Transceiver is going to be a Yaesu 991A. Here are some questions I've run in to that I'm having trouble finding answers to.

    1. We have power lines ~50-60 ft from the start of the antenna is that ok?

    2. What type of wire is best? I've found a bulk spool of 500 ft White Stranded CU THHN Wire 10 AWG, Conductors are annealed (soft) copper, rated at 600-Volt and heat, moisture, resistant, Insulated with tough, heat and moisture-resistant PVC for use n wet or dry locations at temperatures not to exceed 194˚F. Would that work well or should I use something else.

    3. The instructions say sloper is the alignment for the antenna and because it's over 25 ft I dont need a counterpoise or ground. If I dont need either then I'm confused at the angle of the slope I should use and if not using a counterpoise or ground how to I connect the other end of the antenna?

    4. Anything else I'm missing or I havent thought about?

    Thank you everyone 73
  2. KK5JY

    KK5JY Ham Member QRZ Page

    Welcome to the group! :D
    The closer you can place this to the antenna, the better. Placing it at or near the antenna, on the 50-ohm side of your 9:1 transformer, would be best.
    An end-fed antenna is just an OCF that uses something other than the antenna for the counterpoise. There's really no such thing as a counterpoise-less antenna.
  3. KD8ZWI

    KD8ZWI Ham Member QRZ Page

    I have always been taught, that you should be at least 2x the antenna height away from power lines. Don't mess with power lines, they could kill you or someone else. Basically you don't want the antenna to have any possibility of falling onto power lines, or blowing over onto power lines, or in any way contacting power lines.

    I have been taught that the antenna should have as much surface area as is practical - and that open wire (not insulated) is best, however - practicality usually wins over ideal meaning... the weight of the antenna (thicker wire is heavier), the strength of the wire, the method used to hang the wire, and SAFETY (think safety first). I use 14AWG insulated poly stealth and it works well. I have been taught that thicker wire increases the usable bandwidth at a given frequency... although I do not know the math to articulate it more specifically...

    Again, my elmer has always drilled into my head when speaking of the orientation of an antenna is, "What is the purpose of the antenna?"... if it is NVIS positioning should be different than if you are interested in DX (think angle of radiation). Angle of radiation will be affected by the antenna type, the orientation of the antenna, and the topology surrounding the antenna. I have very good luck using an end fed long wire at about a 30 degree angle from ground sloping upward, with the feedpoint near the ground. Verticals also have very good "low angle radiation" for DX. It is my understanding with an end-fed, your feedline will become part of the antenna - use your analyzer to tell you what the antenna is doing - and adjust from there...

    You may consider purchasing the antenna handbook, it is a great resource.

    Be sure to tell us how you do! and how the antenna works!

    Good luck!
  4. N5AL

    N5AL Premium Subscriber QRZ Page

    With respect to Question #2, do the experts here recommend soft copper THHN electrical house wire for making antennas? Any problems with stretching and breakage of the soft copper THHN wire?

    I noted that W9MMM plans on building a 175 foot long antenna. Would either hard drawn copper antenna wire or CopperWeld antenna wire be a better choice for such a long antenna run? Or, is THHN good enough?
    Last edited: Apr 26, 2019
    W9MMM likes this.
  5. KD8ZWI

    KD8ZWI Ham Member QRZ Page

    I am no expert but I do have some practical experience building my own antennas and I am happy to share my limited knowledge... kudos to everyone building their own, it is a very fun aspect of the hobby...

    Any conductor can be “good enough”.... it depends on what your situation is and what you are trying to accomplish. Some people load up the gutters on their houses.

    If you are building a resonant antenna - the wire stretching over time is one consideration (the resonant frequency will change as the wire stretches). Also note, The thinner the wire, the higher the “Q”.

    With such a long wire strength will need to be a consideration.

    I like polystealth wire - it is strong for its size and weight, and in my experience it doesn’t stretch a whole lot. It is insulated, which is not optimal but in my mind safer.

    Look up a “cage dipole” - and read about it, it might help you gain more understanding how the “thickness” of the conductor can affect antenna design and performance. ;)

    Open copper wire in somewhat close proximity to power lines makes me shutter. SAFTEY is the first consideration when putting up any antenna. Also remember Resonant End fed antennas will have high voltages at each end... (well, so does a dipole) don’t want the ends contacting people or pets while transmitting....
    Last edited: Apr 26, 2019
  6. KD0CAC

    KD0CAC Ham Member QRZ Page

  7. W4RZM

    W4RZM Guest

    Hi Mike,
    I run a nearly identical configuration as you mention, down to the choke, only I am running a 41' sloper, peaking at about 21'-25'. I had some 14g solid core wire in the garage I DO NOT recommend that! Took forever to stretch the curls out :)

    I'm also Yeasu FT-991A, no amp, external tuner. I've tried 80m a couple times with the 41', I get out but as you can guess not very efficient.

    I guess my main point is I am a huge fan of this system as it allows me HF 10m down to 40 (my installation seems most efficient at 40m) and is invisible to neighbors. Low SWR (again, external tuner) on 10,20, 40 is a plus for me as well. The key is using one of those "magical" lengths that you can tune multi-band. The 41' seems most efficient on 20m and 40m.

    Use at least 25' feedline or run a counterpoise. This config uses your feedline as one. I grounded my matching unit and reduced noise floor somewhat.

    Good luck!
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Are they high voltage transmission lines or just regular 120-0-120V line drops for service to the house? The only reason this matters is the 120-0-120V drops are considered "low voltage" and not particularly hazardous; the high voltage lines that feed the transformers are anywhere from 4.8kV to way higher voltage and are very hazardous. 50-60 feet away seems very far to me, but I wouldn't run an antenna directly under or over the high voltage transmission lines. Distance "to the side" is fine.
    Should be fine for 175 feet, even if you get ice. Soft-drawn will stretch a bit, so you may want to re-tension it once or twice after installation to keep it from sagging too much. After being stretched by wind, trees and re-tensioning, it will become "hard drawn" all by itself.:p
    A counterpoise or earth ground connection at the unun feedpoint is always a good idea and can help prevent your coax from becoming the counterpoise -- which doesn't necessarily hurt anything, but it's uncontrolled. The "far end" of the wire doesn't need any connection to anything except a good insulator, then rope. If the feedpoint is really up very high above ground, then anything you connect to the "ground" terminal of the unun becomes part of the antenna -- and that can actually be good! Your antenna becomes an off-center-fed "inverted L" and it will have some vertical polarization as well as horizontal, which can be beneficial.

    I wouldn't worry about sloping it, at all.
    You'll need an antenna tuner, if you don't already have one! There's no way in the world that configuration will "match" with a low SWR across several bands. That doesn't make it inefficient, it just demands the use of a tuner. At 175' long it will be bidirectional on 160m and 80m, and start becoming "lobey" (having multiple peaks and nulls) on the higher bands.
    W9MMM likes this.
  9. W4RZM

    W4RZM Guest

    This times 1000. This config demands an external tuner. My FT-991A internal tuner can tune some, not all bands, or even portions of some bands. Save your finals and use a tuner :)
  10. AA5CT

    AA5CT Ham Member QRZ Page

    re: "Balun 9:1 Unun End Fed Antenna Questions"

    W9MMM said: A 1:1 isolation/choke balun will be at the transmitter side of the feedline.

    KK5JY said: The closer you can place this to the antenna, the better. Placing it at or near the antenna, on the 50-ohm side of your 9:1 transformer, would be best.

    What does the other "wire" (on the secondary) from the 9:1 transformer go to?

    A ground stake?

    OR is it simply tied back to the coax feeding it?

    A quickie schematic might be needed here ...

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