The Vertical Experiment Continues.....

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KK4NSF, Feb 1, 2019.

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  1. KK4NSF

    KK4NSF Ham Member QRZ Page

    Hello All....

    After dozens of tests, discussions, debates, researches, and so forth..... here is the latest incarnation of the KK4NSF mini-DXpedition antenna. This one is the best so far, with a nice clean receive, good SWR, and excellent reception reports on transmit. According to the beat up (and borrowed) MFJ analyser, it produces a nice 1:1 to 1:1.5 across the 20 and 40 meter bands without having to use a tuner.

    Remember, this antenna is designed to be hauled across ~1/2 mile of soft beach sand where there are no trees, or much of anything else... so portability is a key factor.

    As you can see, it is a simple vertical base loaded antenna, working against sixteen 25' radials, just like my last test. This one differs in a few important ways:

    First, the whip antenna is now a 17' MFJ Telescoping Whip. As expected, this was a major improvement in both efficiency and portability. The whip collapses down to less than 3' which increases portability, and the extra length makes tuning it much easier.

    Secondly, it uses a MUCH improved loading coil. Since the whip is longer, the loading requirement is much less.... only 7.6 uH on 40m, and Zero on 20m. (For 20m, I simply remove the coil, and tweak the length about 6"). Since I've got a lathe, it was an easy matter to thread a piece of pvc pipe for the coil, and turn some nice threaded end caps to mate up to the base and whip. To keep things simple, I made the coil a mono-band unit for 40m. Of course it took some experimentation to get the coil values just right, since calculators only go so far in predicting the exact loading required.... but once I got the number of turns just right it was easy to make a specific-value coil. So far, it's been dead-on-the-money no matter what soil I've set it up over.... but just in case, we'll be carrying a small tuner on our trip.

    Third, the base has been modified to allow us to use a ground stake instead of a tripod. We also made a stub-base that will fit a sand-auger fishing rod holder, but have not tested it yet. With the wide-open terrain on Sand Island, I'm guessing that the little extra elevation that the tripod gives us probably doesn't help much anyway.... and the weight saved by ditching the tripod might allow us to carry 16 little fiberglass rods to lift the radials. I'm not yet convinced they are required... but hey, if they will help out I'm all for it! ;)

    So... .how does it work? So far, it seems to be working great! Since I don't have a lot of test gear, it's hard to give a lot of numbers, predict the angle of projection, and know for sure what the pattern looks like..... but in use it is obviously better than version 1 (the hamstick w radials), version 2 (the base loaded whip) and my magnetic loop. It collapses down into a nice backpack sized, package and sets up in less than 5 minutes. It seems like a winner to me!

    About the coil: the coil was made on a piece of pvc pipe, threaded on the lathe to 12tpi, with turned aluminum ends with 3/8 threads. It is only 1 3/8" dia x 5" tall overall with ~2" of actual coil. I've run 100w through it with no signs of heating. All in all, it turned out better than I anticipated.... and has been well- received by my radio buddies.

    In fact, I've had quite a few people ask if I could make one to match a 10' whip, or maybe for 80m on the 17' whip and so forth. The answer is of course I can! I can make them for any value, limited only by the size of my lathe and available materials. Now I've got a list of folks I'm making coils for.... so I guess Dave's Handy-Dandy Coil Company might be right around the bend. If enough folks want 'em, I might do a production run. If you want one, just let me know.

    Anyway.... that's the current status of the DXpedition vertical antenna project. Please keep those cards and letters coming! 73 17ft w coil.jpg

    Dave
    kk4nsf
     
    Last edited: Feb 1, 2019
    N0TZU, KC8VWM, 2E0DED and 8 others like this.
  2. NH7RO

    NH7RO Ham Member QRZ Page

    Nice.

    Please add me to your coil list...I'm good on the Zed

    73,

    Jeff, NH7RO
     
    KK4NSF likes this.
  3. AJ4SN

    AJ4SN Ham Member QRZ Page

    Beautiful workmanship!
     
    KK4NSF likes this.
  4. KC8VWM

    KC8VWM Ham Member QRZ Page

    Nice job. I haven't tried those 17' MFJ telescopic whips yet but it seems they would do a lot in terms of keeping everything light weight, portable and efficient.

    I also ditched tripods when operating portable too. There's easier and better ways to support portable antennas. :)
     
    KK4NSF likes this.
  5. AA7QQ

    AA7QQ Ham Member QRZ Page

    See if you can find some old Penn conventional fishing reels. They are cheap at yard sales. Great for rolling up the radials.

    Ed
     
  6. KF9VV

    KF9VV Ham Member QRZ Page

    Well done!

    Please sign me up for a 40 Meter coil. Right now I am running a home made coil and a 16' Bamboo fishing pole for camping, both which are ready for replacement. I mounted it all to the roof rack of our RV.

    Jim
    KF9VV
     
  7. KE0EYJ

    KE0EYJ XML Subscriber QRZ Page

    Very professional, and impressive!
     
  8. KM3F

    KM3F Ham Member QRZ Page

    I use long alum window cleaning three piece poles as verticals with radials for field day use.
    The alum has to be cleaned of Anodizing coating and provision for making sure electrical continuity exist between sections..
    .
    On 40 meters I used a 24 extension ladder with top hat mounted on a utility trailer and tuned with tuner at the bottom.
    .
    Surprise of the FD was absolute no cross band interference between radios running 3 verticals and no horizontals.
    Trying to understand why but not complaining
    No filters used.
     
  9. KB4MNG

    KB4MNG Ham Member QRZ Page

    Very sharp looking finished product. You could sell a ton of theses....
     
  10. KC8VWM

    KC8VWM Ham Member QRZ Page

    I'm thinking that instead of using wire radials, a few of those telescopic whip sections would make it faster and easier to deploy in the field without any need of figuring out how to elevate any wire radials on things like driveway markers, tent pegs etc. Keeping wires elevated is always a problem when working with wire radials, and using stiff telescopic elements easily resolves that problem.

    Additionally, telescopic whips would also make it possible to actually "tune" the radials for use on each an every single band. This is not always the case when using wire radials. It's not always practical to tune our wire radials to work on every band. We often just compromise and cut the wire radials we have for the lowest band we operate on and then hope for the best.

    If designed right and since there are now extra telescopic sections available, it would also be possible to make it function as a multi functional antenna. For example, it could function as both a vertical, or be configured to work as a horizontal dipole antenna.

    Result: Improvement in both ease of installation and actual signal performance because the radial are tuned for every band. No more "wires" needed when using metal telescopic radials. Can be reconfigured to function as two kinds of portable antennas in one. Having two different kinds of antennas available for different operating situations.

    It could also be made lighter by trimming down the aluminum base plate. Making it into protruding "fingers" instead of a full circular base plate.

    If constructed light enough and designed for multipurpose use, it could even be used as an efficient dipole antenna installed on top of a lightweight, telescopic fishing pole type mast like this one:

    fishing pole.jpg

    The fishing pole itself could have plastic clips, loops or Velcro straps installed on it which would hold and store all the individual required pieces attached directly to the side of the fishing pole. Thin RG-316 feed line could be wrapped onto the pole where the brass metal clips are already installed on these poles to accommodate fly fishing line. Quick assembly and length adjustment instructions could be included under the fishing pole rubber end cap. (There's some empty space there) This lightweight arrangement could be easily carried around or even attached to a backpack.

    I think if done right this could become the ultimate, lightweight and high performance portable antenna.
     
    Last edited: Jun 25, 2019
    KK4NSF likes this.

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