I've been looking but so far nothing. Even design software with templates for monopoles, end feds
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$\begingroup$ You want to look by antenna model. Monopole is pretty vague unless it's just a stiff quarter wave wire. If you want an easy antenna to build, look for J-pole (technically an end fed dipole). HT monopoles are theoretically simple but physically tricky to construct in a way that doesn't fall apart. The other common HT monopole is technically a broadside helical or normal mode helical antenna (NMHA), so do a literature search for that. $\endgroup$– user10489Oct 6, 2022 at 23:27
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$\begingroup$ I've found a lot of papers on NMHA antennas, but only a few are basic and general. I've not found any free software to model them, but it's not hard to physically construct them from the general paper guidelines, and then cut them until they're tuned. $\endgroup$– user10489Oct 6, 2022 at 23:32
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$\begingroup$ I am not sure you will find antenna resource ONLY for monopole or end fed antenna.There are older books on specific type of antenna - in you quest you may find William Orr's "All about vertical antennas" a good start. Sources for end fed antennas may be harder to find...My advise is to abstain from any recent books - they are on expensive side and do not really contain anything new . $\endgroup$– Jan HusOct 7, 2022 at 2:22
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$\begingroup$ I'm looking at EZNEC7 but it wont run on linux wine6, $\endgroup$– Galen ACCOUNT BLOCKEDOct 7, 2022 at 18:11
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$\begingroup$ All antennas are dipoles, but sometimes the second pole isn't obvious. $\endgroup$– user253751Oct 11, 2022 at 12:41
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1 Answer
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By "handheld VHF/UHF antennas" I'm assuming you mean the rubber ducky and/or whip style antennas.
As you've mentioned, these are monopole antennas, but electrically short ones. Like an electrically short dipole, shortening a monopole increases its capacitive reactance at the feedpoint — i.e. the antenna would begin to react more like a capacitor than a resistor. So it has a lower radiation resistance and is harder to match to a 50Ω source.
To compensate for this, the antennas need to be "loaded". This might be done more efficiently with a "capacitance hat" at the far end but for handhelds use inductive loading starting at the feed end is more typical.
I suspect that with a whip antenna this is mostly in the form of base loading (see also). There are many other ways of loading a short antenna (pdf), and I iiuc a rubby ducky also uses continuous loading — sometimes called "helical loading" but not to be confused with an actual helix antenna which radiates in a completely different fashion!
For a bit more theory re. loading:
- https://www.rainesengineering.com/articles/SimpleFormulasLoadedAntennas.pdf
- https://owenduffy.net/blog/?p=1736 (more on "Q factor" which affects bandwidth)
There's also the issues of balance and ground plane. (Related to the idea of a counterpoise sometimes called a "tiger tail".)
While a 1/4 λ monopole is different than a 1/2 λ end fed, there is still some concern of balancing the feedpoint — anecdotally the understanding seems to be that the user's hand/body capacitively couples to serve as the ground, but there's some missing links here to relevant theory which I haven't found.
And finally, what about the radiation pattern? Similar to other verticals, the height above terrain and ground plane height/quality considerations will also have an effect on the radiation pattern especially in elevation. (In the azimuth surely the user's body effects it, cf. the "body shielding" used as a transmitter hunting technique. Again there are surely missing links here; perhaps in the cell phone engineering literature there are studies of this?)
answered Oct 7, 2022 at 19:08
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1$\begingroup$ There are two kinds of helical antennas -- broadside (aka normal) and end fire (aka axial). HT rubber ducks are usually broadside. $\endgroup$ Oct 7, 2022 at 23:30