[G3OJV] knows the pain of trying to operate a ham radio transmitter on a small lot. His recent video shows how to put up a workable basic HF antenna in a small backyard. The center of the system is a 49:1 unun. An unun is like a balun, but while a balun goes from balanced line to an unbalanced antenna, the unun has both sides unbalanced. You can see his explanation in the video below.
The tiny hand-size box costs well under $40 or $50 and covers the whole HF band at up to 200 W. The video shows the inside of the box which, as you’d expect, is a toroid with a few turns of wire.
The proposed antenna is an end-fed dipole fed with the unun. These are somewhat controversial with some people swearing they can’t work and others saying they are amazing. We are guessing they may not outperform a perfect antenna system, but we also know that you can have a lot of fun with almost any kind of radiator.
The element is about 33 ft long, but to make it fit, you can bend the antenna to fit your lot. Again, it is probably not optimal, but better than nothing. Erecting a wire antenna like this is easy and just requires some insulators and supporting rope or string. Using thin wire and low-profile rope, you can hide it nearly anywhere.
Does it work? Seems to in the video, at least judging by the SWR. As [G3OJV] says, why not try it before dismissing it?
We’ve seen other options, of course. We’ve also seen these end-fed antennas made with tiny band traps.
Unfortunately there is no link between SWR and Efficiency. So the conclusion “at least judging by the SWR” is not true.
The simpliest example is that a pure resistive 50 ohms dummy load give a nice SWR of 1.0, but does not radiate anything (for a therotical perfect dummy load). This misconception is pretty hard to remove from the brain of the majority of us (i include myself).
the only way to evaluate the TX efficiency is to measure the electrical field at a certain radius all around the antenna while emiting a carrier. For RX efficiciency the method is to compare with another antenna mounted the same way at the same time (not quite easy for the most).
Here is a link to a brilliant article on this fact, written by KL7AJ : https://www.eham.net/article/23317
link to download the pdf format of the article, hosted on the DJ0IP website (a gold mine for antenna, balun ,choke etc ) :
https://www.dj0ip.de/app/download/5816592453/SWR+Meters+Make+You+Stupid.pdf
73, F4IPL
It’s true that low SWR does not correlate with better radiation, but with a high star it won’t work at all so I think these statements mostly mean “the swr is low enough that it could work effectively”
Interesting just last night I passed my technician ham license (KO4VTQ). Now I got my license base station and antenna I am looking at how to install all that. My wife will not like a backyard full of wires and our HOA does not like antennas showing from street.
So now comes the adventure to make this happen. If you have ideas let me know, there are a lot of YouTube videos of various solutions.
Some hams have bought a heavy duty antenna matcher and tuned up on their gutters, downspouts, and even chainlink fence. Most HOAs that I’m aware of steer clear of the flag pole issue due to 1st amendment rights (in the USA) so often a ham will end up having one of the seemingly most robust and expensive flag poles in an HOA shortly after getting their license. This is because either the pole (if conductive) is the vertical antenna itself or if it’s a heavy duty poly (if such a thing exists) then it conceals the antenna inside of it. Also random wires and beams have been installed in attics. There is also the ability to do a short gutter mounted vertical which is visible, but may or may not catch the eye of a passing HOA Karen (male or female.) Setting up your random wire under cover of darkness and then taking it down before morning is possible but a pain. With a heavy duty antenna matcher, you can tune up on bed springs, metal garbage cans, gutters, downspouts, roof vents, and it’s even better if your house is multiple stories because then the house itself becomes the tower/mast. Just watch how much power you run through things attached to the house. You don’t need to have sparks jumping off your gutters!
When I worked for Racal on Bowman we had a day out with the Royal Signals on Salisbury Plain. They had a Clansman radio matched to a wire fence.
Nice to see you here Leon, I always enjoyed what you wrote elsewhere. I wonder whether I could get away with asking a related question, hopefully without appearing too naive.
Intuition suggests that if one took something like one of the “NanoVNAs” being sold for next to nothing these days and attached it to a stonking great antenna like Rugby or Droitwich, it would be unable to return a useful reading. If that is correct, why: one would expect larger antennae to have lower resistance, so is it related to absolute (rather than relative) inductance and capacitance?
I once read of a ham that made an international contact by loading up a pair of reading glasses on his desk. Of course the person on the other end didn’t believe it.
I’ve worked the opposite side of the world (NH,USA to Perth, Australia) on 20M with a shortened G5RV mounted only 4 feet above my roof running a mere 5 watts of transmit power. If that abomination of an antenna could work, almost anything can be made to work if one is patient enough.
As someone who has had a license for a number of years, yet doesn’t spend time in the radio technology (a combination of introversion and just too many other projects), I’m going to ask a stupid question….
… what is an “antenna matcher”? Is that another name for a tuner?
I think the two terms can be used interchangeably.
Yes, the unaware and the marketing scum call it a “tuner”. It does not tune anything!
All it does is match the impedance of the antenna to the 50 Ohm nominal impedance of most amateur radio transmitters to minimize the standing-wave ratio so the said radio doesn’t burn-up.
Note, as mentioned by Nicolas above, even a perfect match does not mean the antenna (or rain gutter, or pair of glasses) will radiate energy worth a hoot.
If the antenna is not properly tuned to a frequency, an antenna matcher can match it well-enough so the SWR doesn’t melt the radio, but it will not improve the antenna’s tune.
bit of a shot in the dark but maybe the glasses were acting as a crude Biquad/Bowtie
Welcome to ham radio. I appreciate the excitement of getting your first ticket–I remember getting mine, and being a VE as well, I have seen that same look of excitement on the faces of many others.
Don’t be discouraged by your antenna situation. There are properly-engineered high-efficiency antennas, and then there are those antennas that 90% of us >actually< use.
I have worked Japan from Arizona with PSK31 and 5 watts into a length of wire dangling out of a second-story window. I have worked cw nearly 2000 miles with 2-3 watts of power and an antenna wire held aloft with a 2-dollar kite.
You can buy lightweight collapsible masts that can erect in a few minutes to hold simple wire antennas aloft (after sunset, when all the HOA Karens have gone to bed– then take it down before dawn.)
There is a link to an article here where I describe a very small, portable antenna that I used in conjunction with my "K9QRP" rig (dog-carried radio). It consists of a few pieces of wire, some banana plugs, and a segmented fiberglass tent pole purchased on ebay. This is not a DX antenna to be sure, but I have worked multiple nearby states with it.
http://www.hpfriedrichs.com/radioroom/k9qrp/rr-k9qrp.htm
The stories about antenna-gutters and attic antennas are true, though I have found that antennas of this type–owing to their proximity to the home and its contents, are often unusable for receiving because of all the hash produced by the switching power supplies in appliances and consumer electronics.
Many hams swear by mag loops. They are narrow-band antennas, but quite small relative to wavelength.
If memory serves, one of the Army training manuals talks about pounding a nail into a tree and using that as a field expedient antenna. If you ground your coax (with a nail) at the base of the tree and locate the "connector" nail some ways up, I suppose this amounts to a lossy Gamma match.
I know for a fact that this idea works with flagpoles, because I've taken my QRP rigs to the park, taped wires to the mast, and worked people in several states.
If the tree thing works for you, you're probably better off going with bronze screws instead of steel nails–which I presume will eventually rust.
Speaking of trees, a lot of times you can toss light gauge wire up into the branches (for use as an antenna) and at any distance, the wire becomes virtually invisible.
First, congratulations on passing your test! Welcome to the hobby of sub-hobbies, the rabbit holes are neverending.
There are a plethora of antenna ideas that will work. Use your favorite search engine to peruse “stealth ham antennas” and you will find dozens of DIY ideas to hide different antenna types. I’ve seen fake vines wrapped around an end-fed mounted in a flower pot on a condo patio, a Purple Martin birdhouse mounted on a tall pole, with the “guy wires” acting as a dipole. A couple hams actually loaded up their gutters as rather inefficient end-feds.
There are companies that make HF antennas disguises as flagpoles. Most HOAs allow flagpoles, right? You can DIY your own as well, check out the Flagpole Vertical in the Green Valley Amateur Radio Club website: https://www.gvarc.us/vertical-flagpole.html That club has extensive experience hiding antennas from HOAs. Take a look at the Magnetic Loop (or Mag-Loop as you’ll find elsewhere) on their site, that style of antenna is very compact and concealable.
Another possibility is an antenna that drops out of sight behind the house, and is only raised at night for more clandestine operation. While more of a pain, it does give you the option of using a more efficient antenna system. Also, take a look at mobile antennas, put to use on a base station system they can be hidden better, or set up for operation and stored easily. A GVARC member in an HOA used a screwdriver vertical antenna on his patio for HF operation with decent results. I have used SS whip antennas with added groundplanes hidden in trees with good results; once the SS elements get dirty they practically disappear.
Most of the ideas you find will be for HF, which unless you operate CW extensively won’t be helpful much; the Tech license primarily has VHF/UHF privileges, with only 10m voice/data and CW in a few HF bands. However, some of the concealment ideas can be adapted for VHF/UHF antennas.
73, KN4YIW
For VHF/UHF, make the antenna double as a TV antenna. By law, in the US, HOAs are not allowed to ban or unreasonably restrict the installation of an outdoor TV antenna. I suppose it could also be possible to use the mast as a HF antenna.
The relevant rules are “OTARD” – Over the air reception devices:
https://www.fcc.gov/media/over-air-reception-devices-rule
They don’t give homeowners carte blanche, but they do restrict HOA’s to “reasonable” rules.
One guy made a fractal antenna, in that it was on a 4 by sheet, and was stapled onto the board. He did that because his landlord wouldn’t let him run a line on his apartment roof. Cellphone antenna use a fractual antenna.
Amateur radio operators – the original hackers.
There have been hackers and tinkerers since humanity began. Radio hams are certainly not the originals.
not Original no, but they were the Icebreaker Hacker/Maker of the modern era
Thanks HAD, I feel like the stealthy HF antenna discussion along with VHF-IR bands are what is going to keep our numbers up so that the FCC wont threaten more spectrum. Too few of us have the opportunity to erect a sweet beam on a tall tower and are forced to stealth antenna and often QRP too, often relying on those old guys with the towers to make a dx.
Stealthy spy rigs are the future with HOAs, but you can still do so much cool stuff with them.
So encouraging healthy Elmers(and Ellaines?) is also so important in an age where too many of the Elmer generation is a dismissive to angry tower measuring and belittling contest, we need to build up the power base in amateur radio of real melted solder and recycled wire hackers who don’t have the budget, space, permission to do what was easy in the 80s.
HAD is for the real hackers, ham radio was among the first real hackers harnessing electrons, thanks!
Loop antenna, random length of wire tied to a rock and thrown over the tree branch, and many other methods used for example by spies and resistance groups during the ww2. Look it up, it’s quite interesting.
I sanction the magnetic loop. Best performing compact antenna ever. If you can figure out how to retune it with some kind of a servo that follows what frequency you’re on, it’s even better.
OCF dipole is just like a normal dipole feeded at around 1/3 of the total length instead 1/2.
I built some for me and my friends, it works fine but it’s long if you want to work 40m
As a ham operator any discussion of antennas requires the obligatory “Please make sure it is grounded!” discussion. I am a general class license holder. I put up a random wire dipole between a tree and a wooden fence spanning back yard to front. Balun was hung in a tree on a pulley so it could be lowered to the ground. One end of the random wire was attached to another tree in the front yard on a pulley so it could be lowered to the ground. The idea was to lower it to the ground every night or in inclement weather. The coax ran through a gap in a window to the station. One night I decided to be lazy and not lower the thing down. that same night an unpredicted summer storm popped up. The tree in front of the house was struck by lightning. Devastating results. Over 4000.00 USD in damages. The electronics in the stove were toasted as was a computer in the station. Because i diligently disconnected the coax from the radio none of the equipment was damaged. The lightning blew a hole in the living room wall and another in the gutter in back of the house. I hope I am scaring you into making sure things are properly grounded. It is easy cheap insurance to protect you, your equipment, andmost importantly, the ones you love. MAKE SURE IT IS PROPERLY GROUNDED!!!!!!!!
You cannot ground an end-fed halfwave antenna. If you do, or add even a small counterpoise, it will become an off-center-fed dipole and its characteristics change markedly.
Not true at all. Please do not spread unsafe misinformation.
EFHW antennas have a lug specifically for grounding. Grounding it will not hurt the performance of the antenna. Attaching a small counterpoise can improve the antenna significantly.
At a minimum the coax shield should be grounded before it enters a structure.
Sources:
http://www.aa5tb.com/efha.html
https://myantennas.com/wp/f-a-q/efhw-antennas-f-a-q/
https://vu2nsb.com/antenna/wire-antennas/multiband-efhw-antenna/
I would never tell anyone not to properly ground their antenna, but in the even of a direct strike, I doubt it would make much of a difference. At high enough energy levels, I gather that things behave more like plasma than electricity as we commonly understand it.
A properly grounded antenna is basically outer shield of the antenna to ground BEFORE entering the dwelling. There are many types of arrestors available. If you have cable T.V. go outside and look where the cable comes to your house. There will be a connector with a ground wire on it that protects the home in the event of a strike. The antenna and coax probably will not be usable after a strike but your dwelling will be okay. Check out the A.R.R.L. antenna instalation guides as a great guide to proper grounding. The A.R.R.L. is basically the authority on all things ham. Also as a side note tall buildings have all kinds of antennas on top that can regularly recieve strikes and survive with no ill effects.
An SWR as close as possible to 1:1 is preferrable – which means, that the power sent out by the transmitter is not reflected back into it. If the SWR is high, then you risk shortening out your power amp / feed transistor/tube.
A low SWR only shows that the power is effectively sent towards the antenna.
But if you want an efficient antenna, you will ALSO need a design that transforms that power into a strong EM field. And that is not measured by the SWR.
So a low SWR is ONE precondition to high efficiency, but not the only one.
HAD thanks for all the response didn’t expect it. Very helpful. I am really a robotics guy not ham.
@KN4YIW you said “Another possibility is an antenna that drops out of sight behind the house, and is only raised at night for more clandestine operation. While more of a pain, it does give you the option of using a more efficient antenna system. ”
I had been thinking about that already and this encourages me. I have a two story house in the suburbs surrounded by very high trees. But the back side of the roof is hidden and perfect for “drop out of sight” and when put up gets very high.
Keep the ideas coming.
Doug
Good, Stealthy, Multi-band Wire Antennas: http://www.n3fjp.com/antennas/
Scott N3FJP is a serious contester (he writes popular contest logging software*) and has nothing but wire antennas hanging in the trees in his back yard.
* Though it’s for Windoze only. Booo. ;)
https://km1ndy.com/diy-491-unun-impedence-transformer-for-end-fed-half-wave-efhw-antenna/
Antenna … ? Short Wave count:
Location of deployment and the propagation.
Thats all. 73
I have no issues with the ended longwire that I run. It was a 73′ longwire I changed it to a 150′ longwire. I’m still using the 9:1 unun with great results. I was going to use a counter poise but used the 73′ that was the original antenna and put it on gnd side of unun. Internal tuner tunes it fo the areas I need to. I’ve even had it on 2m for giggles and had minimal set.
49:1 —- impedance rattio abt 2500 Ohm : 50 Ohm , half wave wire end “hole” … vy high impedance,
this is 7:1 — turns ratio (e.g. 14:2).
and see this .. http://www.aa5tb.com/efha.html
73
Tune in next week for our next project…the balbal
Ham radios are essential for survival and communication in emergencies. Although it can be a reliable tool, there are a lot of variables that affect how well it performs overall. Thank you for sharring this post.