Loop On Ground Antenna

Discussion in 'Amateur Radio News' started by KD5W, Jul 18, 2021.

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  1. WN1MB

    WN1MB Ham Member QRZ Page

    Thanks for reporting that and not being bashful with the red text characters and font size enhancement. Stylish! The amateur radio world is forever in your debt for donning the Captain Obvious leotard and cape to deliver a paraphrasing of the age old suggestion of "as high and in the clear as possible" when it comes to antennas.
     
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  2. MW1CFN

    MW1CFN Ham Member QRZ Page

    Welsh. I'm Welsh. Or Dutch/Polish, if you prefer ethnicities. Sorry your insular worldview hasn't helped on this occasion. And made you appear a little bit racist, to boot.

    Oh, and you appear to have gone off topic in the manner you previously asserted was "important" didn't happen.

    [/QUOTE]
     
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  3. MW1CFN

    MW1CFN Ham Member QRZ Page

    How about ground gain? It's not very often I find plots by the excellent HFTA shown in antenna model discussions (arguments!) Ground slope also seems to be irrelevant to most modellers, but not to those using antennas in the real world.

    Both are very important in the final consideration of antenna performance, because we all (bar a few in low Earth orbit) have ground to put up with, and even gain from. And we don't all live on a desert mesa, where many modellers seem to spend their spare time, fiddling.
     
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  4. PA0MHS

    PA0MHS XML Subscriber QRZ Page

    Soft crimping?
     
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  5. UT7UX

    UT7UX Ham Member QRZ Page

    QRO is the thing that far not easy to deal with as some enviers may suppose. To deliver some 10kW to antenna one needs some 20kW from supply. Plate voltage depends on tube, sure, but we’re talking about up to ten kilovolts so plate transformer, entire isolation, and variable capacitors could not be taken from old TV parts. Even feedline is not easy deal due high voltage and current. And every RFI-related problem becomes much harder to solve. So in fact it is harder to work DX with 10kW than with legal power: obviously the more is power the better are chances to be heard over pileup and QRO stations have their tickets in the first row by default but the more is power the harder is build and manage it.

    They seem just envy. :D When someone has good results especially on the top band this person immediately becomes suspected in illegal power. This is probably because so few hams may build decent antennas for top band so QRO is the only chance to be heard for most of them.
     
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  6. UT7UX

    UT7UX Ham Member QRZ Page

    Modeling software takes the ground into account unless option 'free space' is chosen for particular simulation. So I believe in antenna simulations (and physics overall) more than in ham tales: real antennas perform as close to simulation as carefully they've been simulated. :)
     
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  7. UT7UX

    UT7UX Ham Member QRZ Page

    Take them with a fork and put them into the mouth. For better conductivity it is mandatory to add more chile sauce. That's all!
     
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  8. MW1CFN

    MW1CFN Ham Member QRZ Page

    The point I was trying to make is that models don't take the topography into account (i.e. the enhancing, or degrading effects). That's what HFTA does. This is where the importance of an antenna's environment becomes very, very clear.

    Example: two 3-ele Yagis in different locations within Wales. Much the same antenna, but very big differences, notably at those all-important low angles. Note: this is taking intrinsic and ground gain into account. If unreasonable critics want to complain, I can't help you if your environment is more akin to the red line.

    [​IMG]
     
    Last edited: Jul 24, 2021
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  9. W1YW

    W1YW Ham Member QRZ Page

    Not true.

    What we can't do is try to ignore the facts on how antennas work, when that information is provided us.

    Put very simply, here is how such loop antennas work as you start from the ground (and increase in height as a function of wavelength):

    1) ON THE GROUND/ VERY LOW HEIGHTS-- the transmission line effect produces an out of phase excitation that phase-cancels, thereby lowering the radiative efficiency to poor performance (irrespective of other losses which also occur);
    2) AT LOW HEIGHT-- the transmission line effect diminishes and the radiation is launched towards the zenith and HIGH angles, providing localized NVIS communication;
    3) AT MODERATE HEIGHTS-- the launch angle is in the 20-40 degree range providing short skip advantages;
    4) AT HIGH HEIGHTS ('high and clear' as you said)--the launch angle decreases and approaches the horizon, providing longer skip and fewer ionospheric bounces--which means less propagation attenuation. You lose roughly 10 dB per hop. Hence best DX is fewer hopes.

    73
    Chip W1YW
     
    Last edited: Jul 24, 2021
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  10. W1YW

    W1YW Ham Member QRZ Page

    [/QUOTE]

    British citizens are referred to as 'Brits'. No ethnicity nor disparagement there, nor intended. Purely descriptive.

    All the antenna modeling programs I use include topographical effects.

    These statements do not obviate the physics inherent to LOG antennas--which includes cancellation from out of phase transmission line effect. You can't arbitrarily invoke other factors to shore up the dominant attenuation caused by the transmission line effect--it still dominates the performance in a highly negative way.

    Antennas placed on the ground are poor choices for performance--in all circumstances. Physics defines that fact.

    It is important that our fellow radio amateurs are not misled to believe that laying a loop antenna on the ground will ever be useful as an antenna with something beyond poor performance.
     
    Last edited: Jul 24, 2021
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