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Random Wire Questions.....

WX2MIG

WX2MIG

Still Alive & Well
Dec 10, 2008
730
5
28
39° 19' 23" N X 74° 36' 30" W
Now that I have an antenna tuner that can handle it, I'm thinking about giving a random wire a try.

At this point I'm looking to run it from the tuner, out the garage wall, up to the roof line, around to the back peak, there I'll support the lower end from a PVC pipe insulator and shoot for the highest point in the tree I can get a line over.

Now, as I understand it, I attach the running wire to the one post on the tuner, the thing I'm not sure of is the ground. Do I just use the grounding for the antenna tuner. I have the tuner connected to the central grounding system along with all my other equipment, with a solid copper wire running out to a grounding rod at the front of the garage. This will put the point of ground at the opposite end of where the random wire will run.
Will I need to add another grounding run around to the area where the antenna will be, add ground radials, or will the central ground I already have do the trick.....?

I read an article by a guy named Jack (VE5EE or something close to that) and he claims in order to make a random wire that will load up for every band, you don't want it's total length to be a 1/4 or 1/2 wave length, or any multiple of a 1/4 or 1/2 wave length to any frequency you want to use it on. He goes on to list a table of lengths not to use, and some suggestions on good wire lengths to use. This has something to do with impedance matching at those chosen frequencies......
Anybody have any thoughts on this....???
 

That 'Random' in the name of that antenna is the 'key' part of it. It typically means that it isn't any particular length in relation to wave length for any particular band except by accident. That 'random' length is just the longest length that you are able to put in the air for whatever reason. How well it works on any particular band is also going to be sort of 'random'. If it happens to work pretty good on one particular band, it's going to be because it is fairly close to some 'classic' fractional wave length for that band. Not to mention any characteristics of it's overall 'shape', height, etc, which also have a great deal to do with how 'well' it works. Very basically, it's the 'best' that you can do in the circumstances you happen to find yourself in, considering the limitations you happen to have. In all cases, it's better than nothing. In a very few cases, it may turn out to be the best that you can do without those limitations. A random length antenna is seldom very hugely the absolute best you can have.
The 'ground', or the 'other half' of that random length antenna is sort of random too. It's best to have at least the equivalent 'length' of wire in the ground as you have over it. Considering the losses when dealing with 'dirt', more metal in the ground is almost always better. Will your present 'service' gound work okay? Maybe, and maybe not. It'll 'work', but that doesn't say how well it will work, sort of. Which naturally will depend on your tuner's capabilities. Which is another one of those "bigger is better" thingys.
Does it all sound sort of confusing? It ought to, cuz it is. Just too many variables to make a valid prediction/prognostication. I only know of one way to find out if it's a better antenna than you are using now. Care to guess what that 'way' is??
The only thing I'll say for sure is that if any antenna 'claims', "I am the greatest!", sooner or later it WILL get it's lights knocked out. Typically by something with less 'randomness' to it.
- 'Doc


This is the one that will go over a swimming pool? Make that pool part of the ground system. Usually takes about 1/4 the quantity of water in added salt in that pool. You'll also find that you will float easier than without the salt added. Bronze wire tends to last longer in salt water than copper does. No idea where to find bronze wire. Or fill the pool with mercury! That works even better!
 
i'm assuming that you are going to end feed it vs center feed it.

Make SURE you have a GOOD, short, large size wire connecting from the ground lug on the tuner to your radio ground system. A good ground system is EXTREMELY important with an end fed wire; the ground is PART of the antenna SYSTEM. With an inadequate ground, you can have all kinds of problems from "RF in the shack". Literally, you will feel small shocks or "bites" from the RF when you touch different objects such as your mike or key or the cases of your equipment. You can also have "mysterious" problems in the operation of your rig, weird audio on transmit, etc. Make sure you understand what a "good ground" TRULY is for this type of system.

Also, note, that even with a 100 watt rig, you can have VERY high voltages appearing right at the antenna terminal on the tuner. That long, high voltage, ceramic insulator is there for a GOOD reason. BE CAREFUL

here is a link i found that has some good general info. its not really about just random wire antennas but it's good review type stuff http://www.hamuniverse.com/basicantennas.pdf
 
Last edited:
hookedon6,
I wish I'd seen that site a long time ago. Certainly would have things a bit easier to understand. Haven't had time to get through more than a very small part so plan to go back again.
The only exception to what the author has said, as far as I gotten anyway, is about hams being 'mathematically challenged'! I am not 'mathematically challenged'! I'm just too lazy to bother with it. There's a difference. I do all that math stuff in my head, no calculator, and do it so blindingly fast that I forget parts of it before I can write it down.
- 'Doc


(Ain't that the best excuse you've heard in a long time? I'm gonna remember that one!)
 
yep, it is good info ... i go back to it every once in a while to "refresh" what i tend to forget.

it answers a lot of the "how/why do i do this" type questions.
 
shovel snow????? i wouldn't bother. from what i see of the WX forecast, its' just gonna snow again today up there in the frozin north:love:.
hopefully this will be the last winter storm this year for ya'll.
 

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