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5/8 antenna

Antenna discussions,

Love it.

918 you want a vertical that wil perform on 11 meters and 10 meters.

Get a steppir. Spend a lot of money for it. And it is still just a vertical.

A amateur does not need a antenna coupler.

Build your antennas resonant for the band you want to use it on.

Unless you plan on using an all band doublet fed with ladder line.

then the antenna will control where you talk as multi band single wire antenna has many directional lobes that change with the frequency of use.

With a simple dipole YOU can control what direction your lobes and more important your nulls from your antenna are.

I think antenna building and experimenting is the best part of the hobby, for me any way.

save your self a few $$ buy some antenna books and Walt Maxwells "reflections" book and forget about the antenna coupler. ( some call it a tuner but it tunes nothing)
 
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if you read maxwell's reflections you will learn that atu's tune the whole system to resonance,
reactance in the source and feed-line input are canceled,
reflected waves arriving back at the tuner are rereflected in phase with the fwd wave,
tuners don't fool anything, its a CB myth.
 
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Bob, I wouldn't say it is a CB myth but I would say it is just another example of misinformation being repeated so much it has been taken to be truth. Yeah kind of the same thing but my explanation gets to the root of the issue.

:)
 
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w9cll said:
It would all depend on the what you wanted to do but generally the 5/8 would be better (in theory) but I would rather have a half wave resonant then the 5/8 driven with a tuner.
Click to expand...

It is a better answer than I expected. I will simply state that the 5/8 antenna will have an "antenna tuner" between it and the coax, and actually, if the 1/2 wavelength antenna is end fed it has one as well, and typically more lossy... It doesn't matter that it is on the antenna side of the system, it is still an antenna tuner.

Captain Kilowatt said:
Just a note to throw a wrench into things but the term resonant antennas means the frequency at which the net reactanve is zero and really has nothing to do with SWR. I have used many resonant antennas where the SWR was umpteen to one. Namely various longwires snd an inverted L. The L was resonant on 160m but the impedance was only a few ohms. Let's not confuse the term "resonant " with "perfect match". Resonant dors not mean 50 ohms.
Click to expand...

You are absolutely correct. One of my points was resonance could be achieved in ways other than using specific lengths of antenna. Most people have no idea that that is possible. They see resoance as a guitar string and the note it plays as the resonant frequency. Resonance can aslo be represented by a baseball bat, where one part of the bat you barely notice you hit the ball, and another part you hit the ball and the bat shakes violently in your hands. The antenna tuner has the effect of changing where the ball hits the bat.

For example, lets say for a given frequency that the antenna has an R of 50 and an X of 25. Through the use of a device, say a tuner, or other method (specific lengths of feedline of various impedances or however you achieve it) you were able to feed the antenna with an R of 50 and an X of -25, congratulations, you have resonance.

If you feed an antenna with the same magnitude and opposite sign, you have resonance. That is all an antenna tuner is doing, be it between the antenna and feedline, or on the desk in your shack, and it does actually tune the antenna. Its just that the rise of coax many decades ago caused radio operators to forget that.

If you do use a tuner you just need to make sure you use low loss feedline, and what people treat as the best coax on the face of the planet (LMR-400) is very lossy as far as using a tuner on your desk is concerned. Ladder line is best.

Somewhere around here I have a chart that, for a given frequency, maps gain over a range of antenna lengths. I'll see if I can find it. There is no high point at either of the resonant points shown, instead the curve continues on as if resonance is just another point on the chart.


The DB
 
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Here we go, the chart I mentioned...

resonance.jpg


The blue line is just the raw antenna length, the red line is the given length with an L network for matchign purposes. The antenna started as a 0.02 wavelength center fed doublet, and was extended in 0.02 incraments to 1.3 wavelengths, which is a little past being an Extended Double Zepp. The self resonant points are above the 0.5 and the 1 across the bottom.

As you can see, there are no peaks at self resonant points, and there is actually no change in the curves that represent gain at those points either.

Now I'm not saying that people who tune an antenna without any form of matching for resonance is necessarily wrong, but its also not the only thing you should be looking at...

If you use an antenna tuner you can efficiently tune an anrea somewhat below a half wavelength doublet in this case up to, well, really as far as your tuner will effectively tune. If this were a vertical antenna you would be limited to two 5/8 wavelength elements. This is why it is recommended that when using an antenna tuner at HF to make the antenna as long as possible.


The DB
 
If you already got the tornado, re-enforce the hub or plastic inside or the coils. My friend has one he had it up for 2 months, brought it down for service and found the hub cracked from wind stress. Get a A99 and install a Maco 5/8 GP.
 
15minigrass said:
If you already got the tornado, re-enforce the hub or plastic inside or the coils. My friend has one he had it up for 2 months, brought it down for service and found the hub cracked from wind stress. Get a A99 and install a Maco 5/8 GP.
Click to expand...

That was probably a fluke, most people say its pretty dang durable.
I wasnt able to order the tornado, out of stock everywhere it is sold. Dnj told me he will have more next month so i'll just wait for them to get more. If we still have propagation by then, ill order one.
Not really interested in any of the fiberglass antennas, theres a transformer in the back corner of my yard, bet it would wreck havok on an A99 or imax.
 
i hope you live in a fair weather low ice place,
the only sirio that is anything like durable is the 827 and they are known for open circuit coils and radials howling if its attached to the house without the anti vibration ring,
the other sirio's are weak but they do have the best advertising department,

good luck.
 
there are a few strong constructed 5/8 but they use thicker wall tube & cost a lot more than a sirio,
if you don't get high wind or ice sirio's are ok.
 
Have you considered a SP 500. Got a local that swears by it. I've never owned a new or old (original) but they do what a 5\8 is supposed to do. I did own a maco 5\8 and at 60ft & open fields all around my old qth, it liked to twist in the wind. It did NOT hold up very well. The hub holding the ground radials broke. Once I fixed that the ground radials would fall off from time to time also. Wasn't as broadband ed as I would have liked either. I took it down and went back to my old stand by the imax2k. Just my 2 cents. http://www.hy-gain.com/Product.php?productid=SPT-500
 
Blackcat630 said:
Have you considered a SP 500. Got a local that swears by it. I've never owned a new or old (original) but they do what a 5\8 is supposed to do. I did own a maco 5\8 and at 60ft & open fields all around my old qth, it liked to twist in the wind. It did NOT hold up very well. The hub holding the ground radials broke. Once I fixed that the ground radials would fall off from time to time also. Wasn't as broadband ed as I would have liked either. I took it down and went back to my old stand by the imax2k. Just my 2 cents. http://www.hy-gain.com/Product.php?productid=SPT-500
Click to expand...

Yeah ive heard a lot about the spt500, are they as good as they claim? I'll look into them a little more.

Question on the Imax. Do you have the ground plane kit? Ive read that a 5/8 requires one to work properly. Man id go with one or even the antron if i knew it wasnt going to be noisy and potentially cause tvi. Are these antennas really as prone to that as their reputation suggests? What steps could be taken to eliminate such problems?

And haha minigrass, thanks for the suggestion but thats way out of my price range. Looking to spend 200-250 on the antenna and coax... ill need about 50 or 75ft. I need to measure. Im on a bit of a budget because i still gotta get a mast or the stuff to build one, not to mention the damn grounding rods, wires, and arrestor. Im also needing an antenna switch, tuner, and some better swr/power test gear. This is not going to be cheap, lmao.

This is also a bit of a test antenna because ive never installed anything like this, so i dont know how it will all work out, could get slammed down in an Oklahoma storm. So this is all experimenting for me.
 
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918
i have not had my hands on the new p500, i would try to find out what wall and grade of tube it uses before buying one,

my friends brand new tornado snapped within a week of installing it,
i loaned him an old sigma4 and we folded the new tornado into the trash can,

my sirio 2012 snapped and my vector snapped multiple times,

the record goes to another locals brand new old style sirio vector 4000 that he installed one evening,
when he got up the next morning the upper sections had broken off,

sirio's .049" wall 6063-t832 tube is unsuitable for bad weather areas,

good luck.
 

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