I’m still amazed at the success I’m having with my random wire antenna on 80m. Yesterday, I worked a guy who said he was running 500W. He was, of course, 599 here, but he gave me a 589. There’s now no doubt in my mind that a random wire can be an effective antenna.
On the HamRadioHelpGroup mailing list, there was a related discussion about the “almost random” wire antenna. The idea is that some lengths just won’t work well on one or more bands. In general, you want to avoid choosing a length that is a half wavelength, or multiple of a half wavelength of a band that you want to operate.
Tim, N9PUZ notes:
I have used the 49.2 ft (15 Meter) length of wire on vacation with both automatic tuners and an MFJ Model 16010 tuner with good results for 40, 20, 17, and 15 Meter operation. This is not as good an antenna as a dipole or doublet in my opinion but it’s a workable antenna.
Moe, AB8XA, added:
With all the bands we have at our disposal, finding an end-fed antenna length that’s not near 1/2 wavelength on some bands is tough, impossible for me so far. As far as dodging 1/2 wavelengths, 86.9′ may be the best compromise for most bands. Using 95% velocity factor, I find 86.9′ roughly 1/3 λ on 80 m, 2/3 λ on 40 m, 4/3 λ on 20 m, 5/3 λ on 17 m, 7/3 λ on 12 m, and 8/3 λ on 10 m (2.60 – 2.73 λ). But it is exactly 1/2 λ on 60 m, and 0.94 λ, almost 3/3 or 2 half λ, across 30 m, and 1.95 – 2.00 λ, or 6/3 and 4 half λ, on 15 m.
My IC-718 doesn’t have 60m, so slightly shortening the 86.9′ may make it possible to tune 30 m and the lower, CW end of 15 m. But that might bring the lower end of 10 m too close to 2.5 λ.
It appears to me, with an integrated tuner in the radio, which may not have the tuning range necessary for some bands, or even with a wide-range tuner in the shack, the end-fed brings the antenna inside and close to the operator. A remote automatic wide-range tuner, such as the Icom AH-4 or SGC SC-230, between the end of the antenna and lengths of coax and control cable to the shack, appears to me might resolve that problem.
One of these tuners mounted well away from the shack, and close to the ground to feed the required radials, also offers the opportunity to turn an almost all horizontal wire into an inverted-L. From what I’ve seen playing with some modeling software, adding some vertical portion to the antenna can slightly ease the cloud-burning effect of a relatively low horizontal run on lower frequencies, as well as significantly reduce the depth of the nulls of a long horizontal wire on higher frequencies. But I’m sure no antenna expert. It’s always been my toughest subject.
My antenna is 85-ft. long, so I bet I can get mine to load on nearly any band. My next project is to connect it so an SGC-239 automatic antenna tuner that I have and just see what I can do on bands other than 80m.
Pat - W0IPL says
http://www.w0ipl.net/ECom/NVIS/random-l.htm
Thanks, Pat! Click on the link and you’ll find a nifty explanation on why a random wire shouldn’t really be random and a chart of lengths that you’ll want to avoid……Dan
Nyle Steiner says
I see no reason at all why a 1/2 wave long wire should be considered bad. In fact I think it is one of the best lengths to use if you can load into a high impedance.
I have had good luck operating at least several states away on 40 meters using a 1/2 wave long wire and less that one watt.
BTW a 1/2 wave wire makes it easy to operate without using a ground.
Nyle Steiner K7NS
Nyle Steiner says
Sometimes it is easier to find those who have strong opinions than those who will actually give you good sensible facts when it comes to antennas. Reflecting on this, I decided I had better clarify my statement “easy to operate without using a ground” before I strike someones sensitive spot and waste a lot of heat on this site.
A better way to say it might be: BTW a 1/2 wave wire antenna gives you a much wider choice of what will work as an effective ground.
py1vhf - Anderson says
Guys, when using a tuner like the Icom AH-4 or the Icom AT-120, the manufacturer recomends to stay away from half wavelenght lenghts of wire, because the tuners will “see” a very high impedance and lots of high voltage will result. Also, there is a limit on the impedance these tuners will manage to bring down to around 50 ohms (I think the upper limit is around 8000 ohms).That’s the only reason to avoid half-wave lenght multiples. It has nothing to do with a half-wave antenna being good or bad radiator at all. W0IPL: I think you’ve made a mistake (actually, 3) on your website:
British use the word “metre”, not “metere”. And you forgot to take into consideration the velocity factor of the wire (which is abt 0.95) in the measurements you’ve made.
73!
Anderson – PY1VHF – Macae/RJ
George says
Why is everybody avoiding the 1/2 wave? It is most effective length. It causes smallest interference (TVI) and it needs very much simplified, or almost no counterpoise. Is high impedance the reason? That sure is not the problem after proper transformer is used. Best results ever I had with end fed long wire antenna definitely is 1/2 wave.
Jeffrey says
Okay, I’m feeling stupid but asking a question is one way to quit being stupid.
How should a random wire antenna be connected to the tuner or radio?
Also what is the best way to ground a random wire antenna?
Jerry Repine says
Experiment in most cases. I have had great results grounding to a water pipe opposed to actual ground rod. However, my latest setup has a separate radio to earth and ATU to earth and is working out just fine. Visit my diagram at the QRZ site.
Frank Mooney KI7MJU says
As a new ham still experimenting, I ran 100 ft spool of 14 wire from mesquite tree to 9/1 balun at peak of roof. 50 ft coax to old Kenwood at-230 tuner into my obsolete Kenwood hybrid ts-820. Coax runs 24 ft back under the wire before branching off to shack. Acting as 24ft counterpoise???? Also hanging 7 ft vertical off end of wire to reach magic 107 ft lenghth. Can’t see it has made much difference. Some bands the tuner seems to make a small diference, others not so much. By the way, if you use a half wave length or a magic non harmonic lenghth from chart, how can you call it “random” wire?
Dan KB6NU says
On the SST tuner that I have, there is a two-position terminal strip. The random wire connects to one of them; the ground or counterpoise connects to the other. In my case, I’m using a counterpoise that is approximately 66-ft. long.
John K5MO says
Te SST Tuner (it’s the bronze colored unit?) was the product of Greg Ginn 9f the punk band Black Flag.
Dave KC9TEC says
Try the lengths listed below. These are lengths whose multiples were figured out by Ham Universe. Some were were carried out to multiples of 32 just to make sure they are not near any 1/2 wavelength of any one frequency. A good tuner and an artificial ground will put you in business. 73’s and good luck
The lengths are:
29 35.5 41 58 71 84 107 119 148 203 347 407 423
Mike Baggett says
There is so much misinformation on the web because some folks have not actually tried things but go on what everybody else has said. If someone said 75 years ago you can’t work all bands on an end fed or stay away from 1/2 wavelength then it continues to be touted by everyone from the ARRL antenna handbook to the oldest “experienced” ham.
Here’s how to get any length of wire over 60 feet long to work any band from 160 to 6 meters. Buy an Icom AH-4 end fed tuner (auto coupler), attach your wire antenna wire to the hot end and run a short wire from ground side to a ground rod or counterpoise wire and enjoy. Get the wire up as high as you can. The AH-4 makes everything equal. I have even been about to tune a 1 foot long wire on 75 meters as long as I have a ground attached (not saying it would be work, but it tunes. With the longer wire it does indeed work.
ki5so
Ralph says
Does the length of the wire include from the tuner to the mast where it then travels to the other end?
Dan KB6NU says
Yep. It all radiates.
Ralph says
Thanks
Andrew says
My first antenna, errected in haste was a random end fed, joined to an MFJ versa tuner by coax. Several contacts ensued, with good reports. The fourth contact gave me 5/9 then proceeded to tell me that my antenna setup was not a good idea, and would not work very well. This was my first inkling that perhaps the theory did not always tie in with practice. I still hold this view.
Ed Castle says
I have a Yaesu FC-40 long wire antenna tuner. I have tried every length of wire in the list above. What I really need is a detailed description of what to attach to the grounding lug on the tuner and how to position it. I currently have an 8′ copper ground rod pounded straight into the ground. It doesn’t work worth a crap!
Dan KB6NU says
I would try just a wire laying on the ground. You could try different lengths. I think that will work better than the ground rod.
Frank KI7MJU says
I agree. My 8 ft ground rod is tied into 25 ft of #6 buried 6 inchs under ground horizontally. Thinking of adding another one as well. At 4700 ft in desert, we get lots of lightning and 25-40 winds alll the time. Hard on antennas.
SJ says
Attach your ground to a few 1/4 wave kength radials and the tuner should come to life
Rick KA8BMA says
Reading this post reminded me of this web page: . http://udel.edu/~mm/ham/randomWire/. 85′ on the colored chart should cover 80m – 10m.
James T. Lee NK7B says
I have used “random inverted L wires” a lot, always with either my Icom AH-4 or SG-230 auto-coupler at the feed point and interfacing with a modest 50-ohm coax run of about 125 feet back to the shack. Most commonly, I have used a 119-foot braided copper wire radiator (12 AWG) with its vertical segment about 35 feet and the horizontal segment about 84 feet. The radial ensemble is IMPORTANT with this antenna–after all, it is just a vertical with a lot of “extra wire” hooked on top at 90 degrees to the vertical radiator. I routinely have used no less than 40 radial wires each about 30 feet long.
This is a POTENT antenna on most all bands. The radial system is crucial. Period.
Prem chand says
Can we increase the cable given only 5 m to 10m from ah4 to icom718 I am in the ground floor the long wire starts from the first floor because of 5 m cable suppose if I use 10 m I can put ah4 at top of my parapet wall I propose to use 46 or 85 feet as long wire and what should be the counter poise for 46 feet and how much for 85 feet can use rg6 for I creased length from icom718 to ah4 or rg213
Another query I can use 30 feet inverted v whether I can give hot end and co.d end to ah4 top and bottom and then I will bring through 10m rg213 cable connected ah4 and icom718 in addition to the 4 wire cable which automatically will be the length of the running cable t u 73s de vu2rpc prem kovilpatti
Dan KB6NU says
Yes, you should be able to use a 10m length of coax from the antenna tuner to the radio because the output impedance of the antenna tuner should be 50 ohms.
I’m sorry, but I don’t really understand your second question.
Andrew says
Pretty late on this discussion, but I’d just like to share some notes from my last “random” wire antenna build
Last May, a friend called for help, he moved to a different QTH which hadn’t so much space, so he was thinking to setup a single antenna which could allow him to cover multiple bands; after a bit of discussion, he accepted my idea of trying a “random” wire, so we started from the “good length” (green numbers) calculated by VE3EED (SK) and found here
https://www.hamuniverse.com/randomwireantennalengths.html
the idea behind that lengths is that near 1/2 wave the antenna would have an extremely high impedance, while near 1/4 wave it would have an extremely low one, so staying as far away as possible from those lengths, the resulting antenna would present an impedance around 400…600 Ohm which could be easily matched using an ATU or even just an UnUn
Anyhow, we started by picking the longest length fitting the (limited) available space, which resulted to be 84ft (25.6mt) and, since my friend didn’t have a remote ATU (just am in-shack one), and didn’t want to bring the antenna wire into the shack, we decided to feed the antenna using a 9:1 UnUn and for the latter we selected the design found here
https://vk6ysf.com/unun_9-1_v2.htm
but instead of the Jaycar core, we used an Amidon FT-240-43; anyhow, we also followed the UnUn with a 1:1 guanella choke and boxed everything, at that point, we installed the antenna, given the available space and location, the feedpoint is set near the top of roof at about 30ft while the far end is tied to a pole at an height of about 20ft (not ideal, I know, but that’s what we had)
The counterpoise system was built using several insulated wires placed in parallel and spaced using some piece of PVC pipe going down vertically from the feedpoint (UnUn gnd), the counterpoise wires were cut to be about 1/4 Lambda on the various bands (80 to 10 meters), the excess wire coming down from feedpoint was just laid out on ground (like some radials)
The coax connected to the unun runs horizontally at about 90° toward an air vent and from there enters the building and runs under the roof, that run hosts some #31 chokes (Maxwell chokes) and an “ugly balun” (another choke), the coax exits from the opposite side of the roof and goes all the way down, to the point where it enters the shack, at the entry point, the coax braid is grounded using a barrel connector
Ok, we built and installed the antenna, time to test it; we thought to start by testing the antenna without using an ATU and, to our great surprise, the SWR on all bands (80 to 10 meters) was below 1.5:1… this made me suspicious, I started wondering if there was some mistake and if we just built some kind of dummy load, but since we were at it, my friend decided to try making some calls, and the antenna wasn’t a dummy load at all; long story short, the next days he tried the antenna w/o ATU making quite a bunch of contacts all around Europe, plus Africa, Far East and South America, so the antenna was definitely radiating :D !
Now, I’m not pretending that it’s some “miracle antenna” or “the best antenna” around, but if one can’t put up some more complex antennas or just wants a cheap antenna to “get on air”, I believe that a properly built and installed “random” may fit the bill
Just an additional note; the random isn’t exactly the quietest antenna around, for this reason, last september my friend put up a RX-only loop antenna, and the combo seems to be working pretty well
My 2 cents
Bob Truitt WA4A says
I agree with whoever said that theory doesn’t necessarily follow practical results! In my 60 years of on-the-air experience with random wire antennas and low-powered transmitters in the field, I have come to the “practical” conclusion that these simple wires work so well because: (1) They have no predictable radiation pattern, therefore taking advantage of any propagation direction or angle that might be existing. Remember, most low-powered ham radio is not meant to be specifically point-to-point! I leave that for the military and commercial stations or the “big gun” hams who need DXCC! I simply want to take advantage of any prop that will get me a QSO! (.2) Unless you mess up and install lossy coax feedlines, baluns, chokes or other gimmics, you will have, simply, an almost lossless, efficient radiator! I can’t tell you the number of times I have used anything from a two-foot long end-fed wire to unknown lengths of CATV messenger wire in a pinch! Even wire laid out on dry ground will work as an NVIS antenna! The idea is to experiment and discover what works. Now, admittedly, with standard 50-ohm transmitter (transceiver) output impedances, you will need an antenna tuner most of the time. My favorite is a simple pi-network (two variable caps, one on either end of a tapped inductor) but most commercial “T” or “L” designs work well. So, just put the end of your antenna wire into the center of the tuner’s SO239 output connector and tune for minimum VSWR. Earth or ground radials? Except for operating near a thunderstorm, (don’t do it) sometimes “yes” sometimes, “no”! Experiment! Just some thoughts for those who, like me, tend to operate from temporary random locations where more complex antennas would be a nusiance!
73