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Base Ground Mounted Verticals

Discussion in 'CB Antennas' started by freecell, Apr 24, 2021.

  1. The DB

    The DB Sr. Member

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    Oh hey, look what I found. Its the complete model data, and the other things on the same page as the .pdf file... I mean, why couldn't you have just shown this?

    foundit
    So the elevated vertical has slightly angled radials and no mast, so, why did you mention that a mast is needed to get that pattern shown in the model when the model of the elevated antenna in question has no mast? Looking back up I see the post has been edited and that remark has been removed... Good on you.

    The two ground mounted vertical antennas in the model have no visible radials, so they used the mininec ground, and simulated the radials rather than using actual radials in their models... But it still doesn't say how many radials they simulated... For the reports I have read and the testing I have done, this is a less accurate way of doing things. Its due to the many limitations because of shortcuts they had to make when creating the mininec ground for mininec. I wouldn't necessarily call it wrong, I would just say there are better ways of doing this.

    Having this information available to me, I could duplicate it if I needed to now that I see more of what the modeler did.

    Never said anything about a change in directivity. Did mention that the more radials you have on a ground mounted antenna the stronger the signal in the model shows, but the directivity doesn't change, at lest not enough for the model to report a difference. In the three 1/4 wavelength ground mounted antenna models I made for this (a 4 radial, a 16 radial, and a 20 radial), they all have different gains, but the same directivity...

    0.36 ohms? That number strikes me as rather low. I made a 16 radial model to compare with my 20 radial model and the difference in radiation efficiency going from 16 to 20 radials is 0.34% already 0.02% away from your claim before adding the 40 additional radials needed to get to your 60 radial upper limit. There is still quite a bit of room for improvement here. Another thing to note is I'm not actually using particularly lossy ground, which would mean that adding radials would have an even larger effect on the change in efficiency than they are here...

    Perhaps I was mistaken to associate the 16 radials with what was used in the model you posted.

    This, at best, is nothing but a distraction in front of the concerns I pointed out above. Your really telling this to a modeler who has shown in the past that they are experienced with using this very software? So why don't you actually address the actual concern I brought up, namely you intentionally cutting off part of the model data in your picture... Nope, didn't think you would as you haven't addressed these types of concerns in the past. I mean, is it really that hard to have just shown the entire page in the first place?


    The DB


     
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  2. freecell

    freecell Active Member

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  3. freecell

    freecell Active Member

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    one of the biggest lies in the commercial antenna manufacturing industry with regard to vertical antennas is: NO RADIALS NEEDED. if you see this in advertising, don't walk but run away as fast as you can if you're looking for a high performance vertical antenna.

    the manufacturers have no problem using the outer shield of your feedline as a lossy substitute for the missing "radials."
     
    #18 freecell, Jun 11, 2021
    Last edited: Jun 11, 2021
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  4. sp5it

    sp5it Master of puppets

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    You have no idea how many hams could die for claim "no radials needed"
     
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  5. freecell

    freecell Active Member

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    topbanders know better.
     
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  6. Justme

    Justme Sr. Member

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    My vertical for 160 has 3000 feet of copper wire as radials.....
    No radials no fun no dx on 160...
     
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  7. Bluestone

    Bluestone New Member

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    Quarter Wave vertical works at ground level with 4 wire radials, FOR DX not local
     
  8. Justme

    Justme Sr. Member

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    4 raised verticals that would be, very unpractical with my postage stamp ground i have so i opted for partial burried and partial on the ground radials but a fecking lot of them.
    Seems to work, from the Netherlands South America, USA, Canada, all EU up to the Chinese border, South Africa, Middle east all in phone, no digital no CW.
    I like to do it the hard way... same vertical also used with MFJ998 on 80 40 20 and 18.
    Though i have a horizontal OCF for that as well.
     
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  9. freecell

    freecell Active Member

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    here's something you might find insightful.

    vertical antennas chapter 9: DJ2YA
    https://skp.wodzislaw.pl/download/PLIKI/Anteny/09.pdf
     
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  10. Justme

    Justme Sr. Member

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    Read the part, and have the book of ON4UN low band dxing, that i followed building the antenna/station.
    Anyhow, thanks for the link ;)
     
    freecell likes this.
  11. freecell

    freecell Active Member

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    walter (DJ6QT) is featured in the file that i linked you to along with many other topbanders providing practical and useful information. you're welcome.
     
    #26 freecell, Jul 11, 2021
    Last edited: Jul 11, 2021
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  12. TheBlaster

    TheBlaster Well-Known Member

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    I made 4 "beginner" models for a 3/4 and 5/8 vertical for 28.5MHz and in these models with 30 radials. Feed point at 0.1m (I see this effectively as ground mount) it looks like the 5/8 wins in terms of peak gain at 12 degrees for both antennas and also of output/input signal at 5 degrees.

    I hasten to add I am not an expert here and have a very basic ability of modelling and did not create FP matches so the SWR's are off the scale. Not sure the matches should effect the radiator length vs pattern though.

    I used 300/28.5 x either 0.75 or 0.625 x 0.95 VF to get the lengths of 6.25m and 7.5m for 5/8 and 3/4 wave respectively. My red dot is at 5 degrees. I used "real ground" and values of 30 and 30 for dielectric and conductivity to best estimate what I believe my own QTH ground would be which is likely to be very good ground.

    I see models as a what may or may not happen once antenna is set up in reality. A model is better than nothing to display possible responses.

    Please do point out any glaring errors I am doing it just for fun. 5/8 top image and 3/4 image under edited to add a 1/4 wave for reference.. peak in/out for quarter wave at 22 degrees... and also add 1/2 wave..peak in/out at 16 degrees.

    5/8 Five Eight for 10m band FP 0.1m.jpg 3/4 Three Quarter for 10m FP 0.1m.jpg 1/4 Quarter wave for 10m FP 0.1m.jpg 1/2 Half wave for 10m FP 0.1m.jpg
     
    #27 TheBlaster, Sep 25, 2021 at 11:09 AM
    Last edited: Sep 25, 2021 at 12:00 PM

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