Thursday, October 4, 2012

My favorite "not so random wire" antenna and what I read to make it.

I have been using a random wire antenna for quite a while now. The first one I created was for Dayton Hamvention where my son and I camped at Buck Creek which is an Ohio State Park. At Buck Creek we threw up the antenna about 30 foot into a tree close to our camping site and with about a s2 noise level we had probably the best radio experience to date. Taking a look back at the geography of the area it is easy to understand why. The camping area is surrounded by lake on 3/4 sides and the whole camping area is about 30 foot above the land surrounding the camping sites. This almost entirely made up for the prevalence of Poison Ivy. 
That was the first experience with the "not so random wire" The second was field day. Same results here. The noise was higher being that we were down at the USS COD downtown Cleveland but we still got out fine and made plenty of contacts. The Ohio QSO party was done with the same random wire in my back yard operating "picnic table" portable. This "not so random wire" operated better than my 80m center fed dipole at the home. The location was the same but performance was now. This year we joined the Ohio State Parks on the air competition and activated Punderson. Another location just like Dayton Hamvention. The spot we picked was a good 500-600 foot above most of the surrounding area. So anyhow. because websites come and go I locked this stuff for my records. Here it is. The document I used to create the cheapest.. AND the best antenna I have ever used.

Here it is in play

Original post was here

The "Best" Random Wire Antenna Lengths 
Random wire lengths you should and should not use!
Updated 06-29-2012 

The random wire antenna is probably one of the least expensive, easiest and cheapest HF antennas to use if you have a tuner and you want to get the "most" out of a length of "random" wire without having to pull out that calculator, doing the math, getting the center insulator built or bought, running the feedline, and all the rest that goes with putting up a more elaborate antenna.
All you need for a random wire antenna is some wire, your tuner, one or more supports up as high as you can get them to string the wire from the supports to the tuner, at least one or two insulators and a little time.

One single wire, no solder connections, very simple.... all the way from the tuner to the end support. That's it in a nutshell.....or is it?

Many hams have tried till they are blue in the face to install the random wire antenna that works on most; if not all of the HF bands with terrible results.
Swr usually is all over the place and the tuner will just not do it's job. You can get good loading and low swr on sometimes 2 or 3 bands, but one or more of the bands that you want, just will not cooperate with an swr that can be adjusted with the "tuner".
So after much frustration..down it comes and you go on to a totally different type of antenna....all that time just wasted in your opinion.....until now!
We recently found some good information about random wire lengths that you should and should not use.
Jack, VE3EED, hopefully has solved a major headache we all have when we attempt to go thru the trial and error and frustration with getting the random wire to work where WE want it to work.
He knew that in order for the tuner to "see" a fairly low swr to work within it's range, that the antenna had to be NOT A HALF WAVE ON ANY FREQUENCY that we wanted to us, because a half wave will give us a very high impedance and the resulting swr into a 50 ohm transmitter!
So Jack took most of one day, did the math with the aid of his trusty calculator, several cups of coffee and came up with...............................
In Jack's own words....
"Here's the word on random-wire antennae."
Presented for your consideration by Jack, VE3EED.
The table below represents half wave lengths and multiples that you
You have to stay away from a half wavelength on any frequency.
Therefore, we came up with the following numbers to avoid (IN FEET):
These lengths in the table below are the culprits that cause all of the trouble when using random lengths.
Frequency MHz 1/2 Wave 2nd Multiple 3rd Multiple 4th Multiple

So those are the numbers above that we have to stay as far away from as possible when building a long-wire antenna.

Here they are in order:
REVISED: 16 19 22 26 32 33 38 44 46 48 52 64 65 66 76 78 80 88 92 95 96 99 104 110 112 114 123 128 130 132 133 138 144 152 154 156 160 165 171 176 182 184 190 192 195 198 208 209 220 224 228 230 231 234 240 242 246 247 256 260 264 266 272 276 285 286 288 297 304 308 312 320 322 323 325 330 336 338 342 352 361 363 364 366 368 369 374 380 384 390 396 399 400 414 416 418 429 432 437 440 442 448 455 456 460 462 464 468 475 480 484 494 495 496.
Some of these numbers are too close to squeeze in between them.

Here are the final numbers (in my opinion) in green below that would be good for a long-wire antenna: (You may want to make a note of them)
REVISED: 29  35.5  41  58  71  84  107  119  148  203  347  407  423
REVISION NOTE:  We had a note from James, KB5YN, pointing out that one of my so-called GOOD numbers was 220 feet. That is the 10th multiple of a half wave on 15 meters. Well, I didn't think it would make any difference at that many multiples. However, the radio didn't tune up very well on 15 meters.

So, having nothing better to do one day, I re-did the calculations going out to 500 feet. That meant calculating all the way to 32 multiples of a half wave on 10 meters. I won't bore you with all that so the first portion of this still only shows up to the 4th multiple. There are so many new frequencies to stay away from, that it gets pretty tricky for the longer wires. However, the list has been revised and is good for wires as long as 500 feet.

73.... JACK, VE3EED


For the record I used 107 foot of 16ga wire. I made counterpoises for 10, 15, 20, 40 and 80. I hooked this all up to a 4:1 current balun. The system just works. I have tried plenty of other antennas and the bang for the buck on this setup cant be beat. Sure you have to tune it but it behaves very predictably. 

This system will be going to Southern Ohio soon when my wife and I take a vacation in Hocking Hills near Logan Ohio. I was going to make  or buy a buddipole or something like that but honestly. This antenna works TOO good to replace it. 

1 comment:

  1. Can you be more specific about your counterpoise? How was each one made for each band? Why do you need a 4:1 Balun? Was the impedance too far away that the tuner could not match?