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all bands on long wire?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W9WQA, Nov 25, 2019.

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  1. W9WQA

    W9WQA Ham Member QRZ Page

    ive noticed in various threads that some hams give up on auto tuners and long wires.
    some just accept that one wire just wont tune on all bands and trimming for one looses another.
    heres what i did and ill just use numbers for example, not necessarily accurate .

    i had 80 feet up and got all but 160. i spliced in 20 feet and got 160 but lost 17.? who knows why !!
    talked with my "guru" and he said to use a trap at the splice point. that should get 17 back and still get 160.
    the trap, a ?? turn coil worked. it trapped 17 but 160 got thru.

    thats not too scientific and no formulas were used but it worked.
    others will have different lenghts but its worth a try.
    is the ant a world beater? well mine is up just 16 feet at best , surrounded by trees but it gets me on the air.

    so dont give up with just a straight wire, add some, trap some and tune away...
    btw i started with a a wire cut from a chart and went from there.

    73
     
    AI3V likes this.
  2. NM7G

    NM7G Ham Member QRZ Page

    I'm uncertain as to the meaning of "got all but 160". Does it mean you measured an acceptable VSWR on each band?
    Did you make good contacts on the bands you tried? What is the feedline (transmission line), and which tuner do you use? What earth ground do you use?

    The ease with which you make contacts, and the reliability of those contacts, has always been a priority for me.
    At 16 feet above average ground, RF losses due to the earth degrade horizontal and near horizontal signals significantly, not to mention result in high angles of radiation in the elevation axis; with somewhat better performance very close to the seashore. Because the earth absorbs RF (both transmitting and receiving), your measurements to date have been deceivingly generous. Were you to elevate the wire several feet over it's entire length (preferably many feet), you'd notice considerably different performance. The antenna will be a world beater when on-the-air results you log show many contacts with excellent signal reports on multiple bands. Think height. Have fun.
     
    Last edited: Nov 25, 2019
  3. W9WQA

    W9WQA Ham Member QRZ Page

    im offering info for guys like me, many, who need to get on the air with limited resources.
    btw im near s bend in. and the wire points out sw thru arizona. the guy in hawaii says 'nice signal' same from boston,texas,canada.
    world beater, not meant to be. just hoping to help others, unlike you. your comments
    which simply try to drag me down to feel superior. they mean nothing to me.
    so when you see "w9wqa:' simply ignore the post so you wont feel insulted by my ignorance...73

    btw, i predicted to myself that someone would show up EXACTLY like you did. it happens all the time with ego driven people...
     
  4. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    ANY antenna in the air is better than NO antenna in the air.

    I've worked the world here and there over many years with very poor antennas at various times - it makes it all the more rewarding.

    I used a 25' end fed in a 2nd floor HOA condo, with no proper earth ground, back in 1998 and had plenty of contacts. And before that, various end-fed random wires with a simple homebrew tuner worked lots of stations.

    You work with what you can.

    Dave
    W7UUU
     
    N7ANN, K0UO, KQ4MM and 2 others like this.
  5. AK5B

    AK5B Ham Member QRZ Page

    As Dave implies above; everything "works."

    I suspect the OP's "long wire" is really a random wire (which also "works" at most any height as well).

    A true multi-wave length long wire will rain buckets of signals to/from certain lobes and be deaf as a door nail in the nulls.
     
  6. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Just don't buy an amplifier until you have a decent antenna :)

    Dave
    W7UUU
     
    N7ANN, N1NA, K0UO and 2 others like this.
  7. W9WQA

    W9WQA Ham Member QRZ Page

    i guess i should clarify something.
    i am not in the slightest,smallest , tiny way promoting a long wire antenna 16 feet off the ground. that has nothing whatsoever to do with my thread.
    i simply remind guys who already have a wire antenna that will not tune some bands,,,that the addition of a trap coil may help them as it did me. i stated that the figures were just an example, not measured since my wire is not like yours.
    even the trap is or will be different.
    btw my counterpoise is ABOVE my wire, a 10 by 50 foot alum soffit but im not promoting that either. just know that it works...
    some people cannot resist the temptation to try to correct or teach others others what they think they know better...


    random wire, long wire whatever wire....
     
  8. WA7ARK

    WA7ARK Ham Member QRZ Page

    Adding a parallel-resonant antenna trap with additional antenna length beyond the trap is a time-honored method of adding additional bands to an antenna.

    When deploying a "random wire" antenna, you are in-fact building a variant of a Marconi vertical; a current-carrying wire fed against the earth below it, usually called a counterpoise. The counterpoise is "the other half of the antenna", and can be realized either by driving ground rod(s) into the earth or by building a radial fan (in, on, or elevated above) the earth under the "vertical".

    The trick is to establish a useful current in the antenna wire immediately above the feedpoint, and to recognize that an equal current has to flow into the counterpoise right below the feedpoint.

    Establishing the current in the antenna wire is all about knowing the impedance that exists right at the antenna feedpoint. Electrically, the feedpoint is between two terminals, one of which is the vertical wire, and the other is the common point where the radials come together, or where the ground rod(s) are tied together. That impedance cannot be too crazy; otherwise it will impossible to build a matching network with sufficient tuning range to make the system resonant on all ham frequencies between 1.8 and 30MH, for example.

    It might be instructive to see typical feedpoint impedances for an antenna such as described by Tom, @W9WQA

    tom.png


    It is fed against a counterpoise of 4ea 15ft wires (4-7), elevated 0.25ft above average dirt. The vertical part (1 and 2) is 16ft tall, and the horizontal part (3) is 64ft long.
     
    Last edited: Nov 25, 2019
    K0UO likes this.
  9. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Let's review some terms...

    Long wire: Antenna cut to be one or more wavelengths long at the lowest desired frequency

    Random wire: Antenna of whatever length is convenient based on materials at hand and/or space available

    Loading coil: A coil inserted into an antenna length which lowers the resonant frequency

    Trap: A Capacitor and Coil combination (Lumped Network) inserted in an antenna length that acts to cutoff below a particular frequency
     
    WG8Z, KP4SX, WB5YUZ and 1 other person like this.
  10. WA7ARK

    WA7ARK Ham Member QRZ Page

    ...continuing post #8:


    Here is what EzNec predicts that the feedpoint impedances will be on some useful ham frequencies:
    Tom1.png

    I have circled the frequencies where a limited-range tuner might have difficulty matching those impedances, but notice that 160m is by far the most difficult for a tuner to deal with. For the purpose of this analysis, I am ignoring any transformation that might take place in a transmission line between the tuner and the antenna feedpoint, in other words, the analysis is for a remote mounted tuner like my MFJ-998RT. When you consider a feedline, you have to consider the impedance transformation created by the feedline, the loss in the feedline, the break-down voltage of the feedline, etc.

    So now, I will add 20ft of wire to the horizontal section, which is isolated by from the rest of the antenna by a parallel-resonant trap that resonates just below the 80m band. 100uH in parallel with 22pF is a suitable trap combination.

    So here is what happens to the impedances seen by the matcher with the trap and addional 20ft of wire inplace:

    Tom2.png

    Notice that this "fixes" 160m, while not effecting the other bands hardly at all.
     
    Last edited: Nov 25, 2019

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