160 meter inverted L radials

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KG4DYN, Jan 8, 2021.

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  1. KA0HCP

    KA0HCP XML Subscriber QRZ Page

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  2. MIKESM

    MIKESM QRZ Member

    N6LF's work on radials is really great. This piece was especially interesting: https://rudys.typepad.com/files/qex-may-jun-2012.pdf It seems to say that if you are doing elevated radials you don't want them different lengths, but that 16 radials even are short lengths can be pretty effective, esp if you are willing to make the vertical element longer.

    I was wondering if this was still true if you were doing a fan vertical, where you had a 160 meter L, and also hung an 80 meter and 40 meter element as well? I have a 100+ ft redwood that I could actually easily hang >16 25 ft radials in branches at about 15 ft (making sure the ends were well insulated since they would have high voltage at the tips).

    Rudy's work would indicate that that could work well well for any single band, but I haven't seen him write about a multi element vertical case.
     
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  3. AK5B

    AK5B Ham Member QRZ Page


    FWIW, I had my 10-15-17-20m fan vertical up 8' with around a dozen radials cut roughly .25 w/l and it tuned up nicely on all those bands; I suspect a 40/80/160 version with .15 to .40 w/l radials would do well (Remember that Rudy also specified this range of lengths suitable for elevated radials, too).

    73,

    Jeff
     
  4. K8JD

    K8JD Ham Member QRZ Page

    Since my atennas are mostly in a wooded area behind my house, there are tree roots at the surface and laying radials would be extremely difficut, I opted for the good old, coax fed. halfwave dipoles for 160 and 80 M. I have worked all over North America with this setup with 100 W or less.
    If you are going for top band DXCC , just put up a 312 ft tower with insulated base and feed it as a 5/8 wave vertical on 160 M (have fun getting permits) ! Maybe some amplified loop antennas for low noise reception too.
    Beyond my means to DX on 160 M ! :eek:
     
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  5. MIKESM

    MIKESM QRZ Member

    Jeff, thanks. I don't think I can put elevated verticals in the branches that are 1/4wl at 160, or even on ground for that matter. The specific PDF I referenced has results from relatively short (but uniform and 16x 32x of) radials including 15 ft and 33ft that looked pretty OK. I did a little modeling, and for at least 1 band, they seem to work ok, though the vertical element has to be longer.

    What I haven't seen is anyone looking at this with multiple elements in an elevated radial config like what I could do in the canopy of a tree.
     
  6. AK5B

    AK5B Ham Member QRZ Page

    You're welcome, Mike---I'd still give it a whirl, even if the radials are only 1/8th or 1/10 w/l--or even less, especially if you will have other radials for the other bands---never know for sure until you try. Maybe a remote tuner at the branches/feedpoint could smooth things out enough to make it work FB.

    73,

    Jeff
     
  7. KI4IO

    KI4IO Ham Member QRZ Page

    A plethora of good advice - interesting reading.
    I opted for a 165' inverted-L (75' vertical and 90' horizontal) and a mixed bag of radials, 20' to 65'. Currently 37 radials stapled into the ground.
    I'm not a big DX hound and have little experience on 160 - I did manage 198 QSOs in the recent Stew Perry event running 5 Watts.

    I use the antenna on 80 - 20 as well, switching in L and C matching components remotely using these little wireless devices from
    MyElo. See:
    https://www.amazon.com/eMylo-Channe...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

    While I may not have a perfect antenna on 160, it's an absolute wonder on the other bands - so that's something to consider.

    I sat at the base of the antenna with a tuner and measured the L and C values...then installed fixed-value components in the
    final (waterproof!) box at the base of the antenna.

    I tried to measure the Z of the antenna on all the bands using my nanoVNA, but that method seemed to be imprecise. Not sure
    why. I measured between the wire and ground. Using component values from a tuner at the antenna base was dead nuts.

    A great all-band antenna! Photo of my matching box can be found on my QRZ page.

    Jerry
    KI4IO
    Warrenton VA
     
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  8. KG4DYN

    KG4DYN Ham Member QRZ Page

    Thanks everyone for the goldmine of information! I really appreciate the help.

    Doug KG4DYN
     
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  9. WA7ARK

    WA7ARK Ham Member QRZ Page

    @KG4DYN Doug,

    When thinking about 160m, it is helpful to reverse your thinking. Start with "What can I do for radials?", and then figure out what the radiator needs to be!

    Let me use the simulator to show what I mean: I have the following parametric model of a 160m Inverted-L antenna with only four elevated radials:
    upload_2021-1-11_6-35-15.png

    Here are the parameters of the model:
    upload_2021-1-11_6-37-46.png

    First, with those values for the parameters, I show the feedpoint impedance, swr50 and gain of the antenna for different length radials M, but with the overall wire length fixed at L= 160ft:
    upload_2021-1-11_6-44-15.png

    Notice that the primary effect of changing the radial length M (30ft to 80ft) is to change the reactance X at the feedpoint. The real part R only changes 3 Ohms. There is a small effect on the Max Gain at the radials get longer, but the total delta is only ~0.7dB, which you wont notice on the air...

    For each radial length M, I ask the simulator what the overall wire length L would have to be in order to bring the system to resonance (X~=0):
    upload_2021-1-11_6-53-25.png

    So, you see that it is possible to "tune" the system to resonance only by changing the overall length of the inverted-L (L) as the last step of the design process. For certain ratios of M to L, the swr50 gets quite small.

    Since I have saved this model, I am willing to use it to customize a design... Just let me know your design frequency, number of radials, length of radials, elevation of the radials, the height of the vertical section, and I will tell you how much wire it takes to bring the system to resonance...
     
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  10. K7JOE

    K7JOE Ham Member QRZ Page

    Installed the elevated radial 160M inverted L 90 feet vertical, 40 feet horizontal.
    4 x full sized 135 feet elevated radials, approx 10 ft tall.

    I've done WAS and I am and 41 countries since the ARRL 160M in one month.
    I'm using a Pixel Loop for additional receive help.

    I strongly suggest the elevated radials. Just easier to maintain, less wire, and really simple. 2 works, 4 is better.

    On my setup, they do not encircle the antenna. the elevated radials are in a 180 degree pattern running north, west, southwest due to my property line etc.
    See video here:

    easy to add an 80M or 60M or 40M wire to the feed-point for an added band....
    Mike (WA7ARK) helped me model this antenna a few months ago and it has proven to be potent. Thanks for the help on that, Mike.
     
    Last edited: Jan 11, 2021
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