What are your most innovative but still humble HF vertical antenna designs? - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: June 17, 2021, 10:07:50 pm
content: The most simple environment for an antenna, a small rectangular lot with either a tree or space for a vertical mast monopole (made with wire or a mast) in the middle. How to make it sing? I am assuming that people want a low angle of radiation.

author: bob91343
author_rank: Super Contributor
timestamp: June 18, 2021, 03:08:53 am
content: Time to hit the books. Get a copy of Kraus' famous old book Antennas. He gives some good information on such devices.

author: MartinL
author_rank: Regular Contributor
timestamp: June 18, 2021, 10:34:44 am
content: Some details that would be helpful:1. What bands do you want to work - in particular, what's the largest wavelength you want to use - 40m? 80m? 160m?2. How big is the lot?3. How tall are you willing, able or allowed to make the antenna?4. What is the ground conductivity like at the site?If you're targeting a single band, and have enough space, then the best choice for horizontal gain is a 5/8 wavelength monopole. 1/2 wave and 1/4 wave would be second and third choices in that order:Beyond those basic monopoles, the "innovative" design work is generally about trying to either make do with less space, and/or having the antenna be effective over multiple bands. There's no best answer for all cases - you need to give your constraints to get useful suggestions.

author: TheSteve
author_rank: Unknown
timestamp: June 18, 2021, 03:48:26 pm
content: I'd look at the Cushcraft R5/R7 type vertical antenna's for inspiration.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 18, 2021, 04:17:53 pm
content: Omnidirectional to the horizon? Colinear.In general, you need length along the axis you want a narrower beam on.A colinear is long along the vertical direction, so gives a narrow beam, to the horizon. It is horizontally narrow (and rotationally symmetrical), so gives a broad beam in those directions (indeed, a whole torus in the 3D plot).It's not always exactly the physical cross-section, for example the long-wire and Yagi antennas have directivity parallel to the long axis. There's some hackery between effective aperture and physical geometry, which I don't know much about.It's more explicit with something like a phased array, where the aperture is literally the array itself, and this effectively defines the resolution of the radiation pattern (as projecting the array's grid onto the radiation sphere), as well as the main lobe to side lobe ratio, or something like that. I forget offhand what angles a phased array can reach, can beams be made in (or nearly to) the plane of the array (for a planar configuration)? The Yagi would seem to suggest it can.The underlying truth is, directivity in whatever direction is limited by the bounding sphere (or semisphere for ground plane types) versus wavelength: you simply need a bigger antenna for better directivity. But also bandwidth (the limitation is all three factors together, I think?), so a Yagi isn't terribly wide but can be fairly compact, whereas a wideband dish needs to be, well, a whole-ass dish. Or compare Yagi to log periodic, which are similar in directivity, but the log periodic is much wider (longer elements).Tim

author: A.Z.
author_rank: Super Contributor
timestamp: June 19, 2021, 07:28:16 am
content: Quote from: cdev on June 17, 2021, 10:07:50 pmyour question lacks a number of needed informations; which frequencies are you interested into ? Are you allowed and/or can you put up a tower ? Can you put up support structures like a tower or some poles and, if so how much high ? Is your environment RF quiet or does it have a bunch of noise ? What's the approx size of the lot ? The ground is grass or other material ?Waiting for answers to the above, some antennas which generally work well on multiple bands are the skyloop, the ocf dipole and the double T-bar vertical

author: cdev
author_rank: Super Contributor
timestamp: June 23, 2021, 01:16:40 pm
content: Yes, I could put up a pole (assuming its not too expensive) A tower is too expensive for right now but would be great in the future, but right now I am just thinking about HF DX, not VHF-UHF so much. I have two fairly tall trees too.My RF environment is very noisy. I have lots and lots of people living nearby, and some businesses too. The 80-10 meter HF bands are what I'd like to have a functional antenna for.I remember recently you were talking about some innovative vertical with a capacitive hat?I want an antenna that can be fed with coax with maybe an autotuner at its base but more likely an antenna tuner in the shack if needed. And I need to also think about lightning protection. Lightning strikes here, enough to have left its telltale scar (a black stripe of carbonized wood) on many local trees.

author: cdev
author_rank: Super Contributor
timestamp: June 23, 2021, 01:46:49 pm
content: Quote from: T3sl4co1l on June 18, 2021, 04:17:53 pmOmnidirectional. Ca be vertical or horizontal polarization, but probably vertical will be what works best here? I have roughly a 20 by 30 meter rectangle lot with two big trees and many smaller trees in the far back.And a detached garage on the right in back. A colinear at the HF wavelengths would be out of the question for me, I suspect. (although I have built them and had success using them for UHF and wifi, etc.. Something broadband like a fan dipole that could rotate, would be interesting. But the rotators for HF antennas are too expensive for me.Quote from: T3sl4co1l on June 18, 2021, 04:17:53 pmIts entirely possible that I might be able to string a very long wire that was inconspicuous a very far distance in the woods behind me inconspicuously, far beyond my lots borders, in back. I would have to use pretty strong non-stranded wire in a dark color. Ive always been curious how that would work.Another option for 10 meters is a dedicated 5/8 wave vertical antenna, which has maybe one or two DB more gain than a half wave end fed. And a low angle of radiation. 15 meters might be possible too for that. There are new bands, which would allow DX with smaller antennas when the sunspots perk up a bit.Quote from: T3sl4co1l on June 18, 2021, 04:17:53 pmSome kind of switched or phased array might be the bestoptions given the small lot. The lot I live on is a very average sized lot. Its not particularly large or small, its an average suburban lot. But I am fairly interested in antennas and would love to have a switchable directivity, if it worked well. I could put poles in the four corners and suspend something from that.

author: A.Z.
author_rank: Super Contributor
timestamp: June 23, 2021, 01:48:20 pm
content: Quote from: cdev on June 23, 2021, 01:16:40 pmNot really innovative, capacitively loaded dipoles have been around for a lot of time; the antenna you're referring to is the "double t-bar vertical", and a version of such an antenna is describedhere, if you take the time to read the whole description, you'll see that it's just a regular vertical dipole, but it's shortened using a pair of capacitive hats at both ends of the dipole arms and it's fed at a side instead of being fed at center (another design may be foundhereand if you seek online you'll find more infos); the advantage of such an antenna is that, even if installed at low height (say 1 or 2 ft) it will offer a low radiation angle which is pretty good for DX contactsAs for the RFI environment, since the above antenna will leave you enough room, you may install a LoG (Loop on Ground) receive only antenna, that one is describedhereand you can find furher notes about ithereThe combo (t-bar and LoG) will give you pretty good performances, the t-bar will give you an omnidirectional and low angle radiation, allowing to put out your RF where it's most needed for DX, while the LoG will allow to set the signal to noise ratio and pull out signals even if you are in an RFI "dense" environment, plus the combo won't cost you an arm and a legAs a note, the t-bar could also be built using wires, seeherefor an idea, in your case the wires may be tied to the treesAlso checkthis pagefor further informations about the t-bar

author: cdev
author_rank: Super Contributor
timestamp: June 23, 2021, 05:40:25 pm
content: Thanks- I'll have to take some time to read through this thoroughly. I use something like this a lot for VHF-UHF reception with a balun in the middle, and widened elements. like a vertical bowtie antenna.Quote from: A.Z. on June 23, 2021, 01:48:20 pm

author: A.Z.
author_rank: Super Contributor
timestamp: June 23, 2021, 06:00:26 pm
content: It's just a vertical dipole, shortened by adding capacitive hats at both ends, nothing special, but has the advantages of offering low radiation angle even if placed low and onnidirectional polar pattern like a vertical... but without the need for radials ... which leaves room for a LoG receive antenna

author: A.Z.
author_rank: Super Contributor
timestamp: June 24, 2021, 03:58:08 pm
content: Quote from: A.Z. on June 23, 2021, 06:00:26 pmJust in case, check the attached imagethat's the basic "t-bar", the feedpoint is at center of the vertical portion and, if you remove the top and bottom "hats" you'll see that it's a vertical dipole, to calculate its size you start by calculating the size for a regular dipole obtaining the overall length and the arms length, now, a coarse formula to calculate the vertical arms and the hats is to assign to the vertical arms 1/3 of the overall lenght and to the caps 2/3 of it; given that you have a couple trees, you may try building a simple "t-bar" by using some length of wire to form the hats and the vertical portion of the antenna, the horizontal (hats) wires will then be tied to some ropes going to the tree and supporting the whole structure, including the vertical wire forming the dipole, the antenna could then be fed by coax using a 1:1 balun, the feedpoint may either be placed at the middle (as in the attached pic) or at bottom, in the first case the coax should leave the feedpoint either horizontally (for some lenght) or at an angle of not less than 45°, in the second case, the balun will be attached to the bottom of the vertical arm and to the middle of the bottom horizontal hat and the coax may just run on ground from thereIf you want to try running some NEC simulations, the code for a simple model of the t-bar can be found belowCode:CM .CM Double T bar verticalCM .CE' setup paramsSY freq=14.250SY wire=0.00125SY wave=(300/freq)SY base=1SY leng=(wave/2)*0.954SY half=leng/2SY arms=(half * 0.3)SY hats=(half * 0.6)SY uppr=(arms*2)+baseSY cent=arms+baseSY lowr=baseSY segv=21SY segh=11GW 1 segv 0 0 cent 0 0 uppr wireGW 2 segv 0 0 cent 0 0 lowr wireGW 3 segh 0 0 uppr hats 0 uppr wireGW 4 segh 0 0 uppr -hats 0 uppr wireGW 5 segh 0 0 lowr hats 0 lowr wireGW 6 segh 0 0 lowr -hats 0 lowr wire' standard groundGE -1GN 2 0 0 0 13 0.005' loadingLD 5 0 0 0 58000000' feedpointEKEX 0 2 segv 0 1 0 0' frequencyFR 0 1 0 0 freq 0ENjust load it in 4NEC2 and see what comes out, notice that you can change the base resonance frequency just by changing the "freq" symbol value, also, in the model the feedpoint is placed at bottom, since it's easier to feed the antenna from there, but willing to move it to the middle of the vertical bar, just change "EX 0 2 segv 0 1 0 0" to "EX 0 2 1 0 1 0 0"; also, if you'll run some simulation have a look at the radiation pattern and also run a frequency scan over the design range (band)

author: Teledog
author_rank: Regular Contributor
timestamp: June 24, 2021, 11:40:49 pm
content: Design?$5 at a Montana thrift store!Stick that puppy on your 1969 V8 station wagon & viola! Instant CB road warrior!G'luck!

author: radiored
author_rank: Newbie
timestamp: July 01, 2021, 12:38:51 pm
content: I have been using a DX Commander for 80-6M, which is a fan dipole vertical with a reasonable number of radials. The maker of this antenna, Callum M0MCX, encourages others to experiment, and has a large number of YouTubes exploring different questions on multi-band verticals, phased arrays, radials required, why a 5/8 wave is not always as good as a 1/4 wave. He leans heavily on the work of Rudy Severns, L. B. Cebik and others.I hope this is helpful.Rudy Severns:https://www.antennasbyn6lf.com/Article by Mr. Cebik:http://webclass.org/k5ijb/antennas/Vertical-antennas.htmDX Commander website:https://www.m0mcx.co.uk/Discord server ishttps://discord.io/dxcommanderYouTubes:https://www.youtube.com/user/m0mcx

author: cdev
author_rank: Super Contributor
timestamp: July 01, 2021, 04:27:00 pm
content: Thank you. Fan dipoles ae interesting for their broadband nature. I will check out this design, Presumably the dipole is decoupled from the feedline by a broadband transformer of some kind at the feed point. This has worked better for receiving for me than the so called infinite balun design. I have had very good luck with sveral differentbroadband antennas that resemble dipoles, the planar (circular) disk, the bowtie, etc. and then a balun at the center, They work best IMHO when care is taken to make a good balun and 1:1 is the ratio Ive had the best luck with for coax.. fed from the side. That works very well for me. at Vhf/UHF. You can also run the feed up from the bottom but that is more noisy. Then the antenna picks up more feedline junk. Then one needs many CM chokes to suppress that noise.

author: tautech
author_rank: Super Contributor
timestamp: July 02, 2021, 10:47:52 pm
content: J PoleSimple and easy to build.https://m0ukd.com/calculators/slim-jim-and-j-pole-calculator/Tuning them precisely is important if you have limited RF power to work with but simple enough with a VNA.Did this one and it works great:https://www.eevblog.com/forum/rf-microwave/antenna-project-log/

author: cdev
author_rank: Super Contributor
timestamp: July 23, 2021, 08:53:36 pm
content: A j-pole on HF?I could see that as working well on 10 Meters. But lower frequencies, wouldnt that be basically an "end fed" antenna (if it was resonant) and nonresonant vertical with impedance transformation. Depending on impedance transformer and orientation, this can work quite well, or not, it depends a lot on the lengthI've successfully built my own knockoff of Ed Fong's DBJ-2 (the roll up antenna) J-pole dual band antennas, although I should try to improve it a bit, still its not tuned as well as I think it could be because it needs to be away from all conductive objects nd dense walls to tune. I dont have a good place to tune it. It needs to be a fair distance from wires, walls, etc. to be tuned properly. I stupidly tried to use a fishing pole to hang it away from my window, but I stupidly use a carbon fiber fishing pole which affected the tuning. So I was unable to get the lowest SWR exactly whre I wanted it. Also, I wanted to use wide coax, say rg-58. I used really thin , old Belden RG-174 which works okay, and is easy to cut. The DBJ-2 is a difficult antenna to tune right even if you have a VNA. It turns out to be really important to get it out away from things.Quote from: tautech on July 02, 2021, 10:47:52 pm

author: tautech
author_rank: Super Contributor
timestamp: July 23, 2021, 09:41:01 pm
content: I had no problem obtaining this sort of result at 315 MHz but at LF YMMV:

author: iMo
author_rank: Super Contributor
timestamp: July 25, 2021, 10:03:20 am
content: EFHW vertical. No counterpoise needed. Could work as a multi-band one without a tuner.

author: A.Z.
author_rank: Super Contributor
timestamp: July 25, 2021, 10:49:38 am
content: Quote from: imo on July 25, 2021, 10:03:20 amno counterpoise means that the antenna system will use something else as its counterpoise, Mr K law must be obeyed

author: E Kafeman
author_rank: Regular Contributor
timestamp: July 25, 2021, 11:01:08 pm
content: Quote from: A.Z. on July 25, 2021, 10:49:38 amVery true.Single pole battery as well as antennas are less functional, as they both have zero output voltage.There is no new innovative antenna design invented in this range, halfwave or shorter vertical antennas, since 100 years.