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[Articles Home]  [Add Article]  

The 25-Foot Untuned Vertical -- 7 Bands

from Dave Benzel - KD6RF on October 16, 2012
View comments about this article!

With the interest in 43 foot untuned verticals, and some of the less than accurate claims being made, I thought I’d share the results of a 25 foot untuned vertical antenna I developed a few years ago. Hopefully, I can shed some more light on its practical use, as well as show how to gain a bit more performance.

The 25 foot vertical is qualitatively similar to the 43 foot vertical, but at half size, and is designed to provide acceptably efficient operation from 40 meters to 10 meters. So, the information here will roughly translate over to 80 through 20 meter operation of the 43 foot vertical (or, even better as you will see, a 50 foot vertical).

I started with the same general idea that the 43 foot vertical starts with – maximum frequency of operation limited to an antenna length of about 5/8 wavelength, above which lobing occurs and low angle radiation suffers.

In addition to ground losses, efficiency is largely determined by feedline loss, and in general, high VSWR starts killing efficiency at the upper end where VSWR starts hitting 20 plus, and at the low end where radiation resistance falls and where VSWR really skyrockets. There are excellent write-ups about this by WX7G here and VK1OD here (I’m new to this board, so my apology to others I may have missed!)

So, my goal was to design a system with less than 3 dB overall loss (excluding tuner loss) and has close to 0 dBi performance by:

• Reducing VSWR at the high end to reduce feedline loss in the 20 plus VSWR region.

• Reducing VSWR at the low end to reduce feedline loss in the 50 plus VSWR region.

• Using a minimalistic ground system.

• Retaining lobe-free low angle radiation over the entire frequency range.

(Note – EZNEC model segmentation was standardized for consistency with “minimum recommenced” at 40 MHz for all data presented here. It’s not hard to get a dB or two different answer if differing segmentation is used.)

Lowering the VSWR Throughout the Frequency Range

Not surprisingly, the first 2 goals are met by lengthening the antenna radiator – VSWR at the low end drops and radiation resistance increases as we start approaching ¼ wave, while VSWR also drops at the high end in the region of ¾ wave. As a consequence, feedline losses drop. Also, as the antenna is lengthened, we relax the requirements placed on the ground system.

Here is the effect of lengthening the antenna from 21.5 feet to 25 feet:

Re-Lowering Radiation Angle at High Frequencies

But of course, lengthening the antenna beyond 5/8 wavelength means we are killing low angle radiation at the high end of the frequency range as shown here for 29 MHz:

What to do.... What to do… In words, we want the antenna to have the desirable low angle radiation of the short 21.5 foot antenna, while retaining the desirable VSWR characteristics of the 25 foot antenna. We need a frequency dependant shortener!

The “shortener” is just a grounded 4 foot mid loaded spike near the base of the radiator which is tuned to a bit above the highest frequency of operation (10 Meters). The idea is to have lots of current flow at 10 Meters (and to a lesser extent at 12 Meters) which effectively shortens the antenna and brings down angle of maximum radiation, while have little current flow, and little effect, at low frequencies.

Here is the radiation pattern at 29 MHz with the “shortener”, showing decent low angle radiation. Gain at 20 degrees elevation goes up to 3.6 dB (compared to 0.6 dB without the “shortener”):

And, at the low end we see that the input impedance remains mostly unaffected (and, with God and Mr, Maxwell smiling upon us, the high end VSWR actually becomes more favorable), which shows that we still have the desirable impedance and VSWR characteristics of the full 25 feet:

A Miminalistic Ground

A big topic, with lots of possibilities. Much has been written about ground – some of it is even true ☺.

Here is the approach I took for this design – A raised feed point (5 feet in this case), and a long metal fence as ground/counterpoise. Raising the feed point relaxes the requirement on the ground system by moving the counterpoise away from lossy earth. There are a few nice write-ups regarding raised feedpoint verticals.

Most or all of them assume use of a set of tuned radials. A really nice and efficient system, but it is starting to become a pretty complex and real-estate consuming project to hoist a radial system up in the air.

Always being one with a eye toward Madman Muntzing, I did the modeling and analysis of a long metal fence for use as a grounding system.

It’s always a matter of concern and debate as to how one measures and compares performance of one system over another. The 2 metrics I usually use are:

• How do the R losses of the system over “real” ground compare to the same system over “perfect” ground.

• How does the real-earth far-field absolute gain of the system compare to a similar reference system at the same height?

Fence Ground with “real” earth (0.01S/M) vs. Fence ground with “perfect” ground – this gives us an idea of how much loss is contributed to the system by ground resistance:

Feedpoint resistance increases only a moderate amount at 40 Meters, and results in 2.2 dB of real-world loss due to Fence ground system resistance. Good enough for my purposes given that the alternatives are a much more complex ground/counterpoise system.

Fence ground with “real” earth vs. 50 radial with “real” earth, at same feedpoint height – this gives us an idea of how the system performs compared to a similar, but more complex, “optimum” system:

The far-field gain difference between the Fence ground system (-0.8 dBi) and the 50 radial system (1.8 dBi) is only 2.6 dB – a value which I find to be perfectly acceptable in trade-off with ground system complexity.

How Good is my EZNEC model?

EZNEC and other modeling software is great, but do they actually reflect reality?

The qualified answer is – Yes!, provided one tweeks the model to reflect reality. The model I used for this project was tweeked by using a small element at the base of the antenna to force EZNEC to actually feed the antenna near the base (oddly enough, this is quite critical to get model results that match measurements), and by shifting around “real” ground conductivity, in my case to 0.01 S/M.

Here is the side-by-side comparison of my EZNEC model vs. Measured data (HP8753 vector network analyzer, 64 averaging) for the 25 ft vertical:

Feedline Losses

No system, especially one the operates with high VSWR over much of it’s range like the 25 ft vertical (or the 43 foot vertical) is complete without considering feedline loss. Again, there are very good write-ups out there by WX7G and VK1OD and others.

I my case, I had a nice chunk of 7/8” heliax laying around, and just used that for the 15 meter long feedline.

Here is the feedline loss (using VK1OD’s enhanced calculator) and worst case assumptions:

It’s nice to have heliax laying around ☺. If you are thinking of buying some line for a system like this, you may want to consider the old reliable LMR-400, but in it’s 75 ohm version. Using 75 ohm line buys us a about 1 dB in reduced line loss. Of course, you could put a remotely tuned Tuner at the antenna, but that can pretty pricey pretty quick.

The Whole System

Shown below is the system performance of the whole system (sans Tuner, which is a whole-nuther topic in and of itself):

Including feedline loss (but excluding the tuner), the overall gain is:

Note that I have included 5 MHz data. We might be able to get away with using the system on 5 MHz, but 3.8 MHz is not really practical. We could add a loading coil to for 80 Meters (160 Meters for the 43 foot antenna) to lower the feedline loss, but coil Q would be an issue, and the shear magnitude of the voltage extremes are pretty problematic (ask me how I know ☺ ).

Conclusions

A very simple system is shown here that:

• Is long enough to provide low VSWR at the low and high ends of the frequency range

• Has a “shortener” that prevents high angle lobing and radiation at 10, and to a lesser extent at 12 Meters, while not hurting efficiency at the 40 Meter low end.

• Has low feedline losses over entire 40 to 10 Meter range.

• Has reasonably near 0 dBi gain over entire 40 to 10 Meter range.

• Uses an existing metal fence line as a fairly efficient ground/counterpoise.

• Decent low angle radiation over entire 40 to 10 Meter range.

It can’t get much simpler:

As always, any comments or corrections are welcome.

Member Comments:
This article has expired. No more comments may be added.
 
The 25-Foot Untuned Vertical -- 7 Bands  
by NY4D on October 16, 2012 Mail this to a friend!
Nice article. I have used a similar setup though with a 31 foot vertical.

One thing is not clear. You say "The “shortener” is just a "grounded 4 foot mid loaded spike near the base of the radiator which is tuned to a bit above the highest frequency of operation (10 Meters)."

I take this to mean you are using an additional short tuned counterpoise, in parallel with the fence, with this counterpoise tuned to be resonant around 30 MHz. If this is not the case you might want to explain better as this seems to be one of your major points.

 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by W8JI on October 16, 2012 Mail this to a friend!
The article seems clear to me about the "shortener".

It looks to me like the "shortener" is really what people traditionally call a "decoupling stub", or "parallel element", just like the HyGain Hytower and many of the ground independent multiband verticals (or a fan dipole) use.

If you look carefully at the EZNEC "view antenna" screen-shot posted in the article, you see a second, much shorter, coupled vertical element. I believe that is his "shortener". Unfortunately, as I read the text, it is coupled to a ground rod. That is a connection that EZNEC and other models do not calculate loss well.

Also, feedpoint impedance cannot tell us efficiency except in very specific cases. It is pretty well known among people who have MEASURED field strength that it is very unreliable to use feed impedance to determine, predict, or verify ground loss.

Impedance agreement alone does not verify pattern or efficiency. As a matter of fact, the pattern calculated by EZNEC does not include ground wave. It is at "infinite" distance over flat earth, so the low angle null is really not there, except at or near zero degrees at extremely long distances.

My take away is:

1.) A decoupling stub or parallel element can improve high end pattern and impedance

2.) Heliax will reduce mismatched feedline loss

3.) A fence can be used as a ground, with some reduction in efficiency

All of which seem perfectly sensible and reasonable to me, although I certainly would not couple a parallel element to a ground rod!!!

73 Tom


 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by NY4D on October 16, 2012 Mail this to a friend!
W8JI - I guess that is my point, it isn't real clear what the arrangement actually is. Looking at the pic doesn't help much, a close up would probably clarify it.

Squinting real hard I think I see a parallel element. But after re-reading I think it is in parallel with the feed and not the ground...?

So to discuss further I think we need the author to explain exactly what he is doing.
 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by N2EY on October 16, 2012 Mail this to a friend!
I think someone just reinvented the Gotham Vertical.

73 de Jim, N2EY
 
The 25-Foot Untuned Vertical -- 7 Bands  
by WX7G on October 16, 2012 Mail this to a friend!
Nice job on the antenna and on the article!
 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by N4JTE on October 16, 2012 Mail this to a friend!
Nice presentation but I wonder how it works.
Your lookups on qrz are are quite low, perhaps you are a new ham. Congrats on a nice technical presentation, hope to hear you on the bands.
Bob
 
The 25-Foot Untuned Vertical -- 7 Bands  
by KD6RF on October 16, 2012 Mail this to a friend!
Hi All,

Sorry, I should have been clearer about the "shortener".

If I can figure out how to edit the article, I'll post a better pic.

The vertical element box itself is mounted on a concrete bedded fence post for mechanical stability, and is in the foreground, about 1 1/2 feet in front of the fence. It is a cool old FAA badged box, which once contained some matching components, but is now just used as a connector holder and nifty ceramic insulator through which extends the vertical element itself.

The housing is wired to the metal fence a foot and a half re-ward.

The "shortener" is attached to the fence (soldered brass plate). It is just a short mid-loaded 4 ft parasitic element tuned to around 32 MHz, much like a director. In fact there is some asymmetry on 10 Meters, about 1.5 dB worth in the plane which contains the vertical and the "shortener".

So, it's not on a ground rod, it is right at the attachment point to the fence, at 5 ft height.

I found it useful to think of it as a sort of frequency dependent transmission line extension, that raises the feedpoint higher at 10 Meters (therby effectively shortening the antenna), while pretty much being invisible at lower frequencies.

Thanks for the constructive criticism Tom - I usually leave the modeling to the experts, but though I would throw this out there anyway :)

I don't place a huge amount of faith in models without verification of real world data, but found it nice that there was very good agreement in impedance, and gave a bit of confidence that twiddling the antenna in the model would at least give qualitative guidance.

Perhaps one other take-away would be to note the we need the shortenenr in order to restore low angle radiation at the high frequencies - because the vertical is now too long. And I purposely made it long to pick up some precious radiation resistance ohms at the low frequency end, in order make a crappy grounding system not quite so crappy.

If my modeling of the fence ground vs an elevated 50 tuned radial system is valid, then we are about 2 1/2 dB down from the tuned elevated radial system. That makes my lazy bone happy.

 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by KD6RF on October 16, 2012 Mail this to a friend!
Bob - have been a ham since sometime in the early 70's - yikes!

How does it work? - well, I put this in a few years ago and have around 150 countries logged, so it does put out. Of course, on-air anecdotal data doesn't mean that much, but at least it's better than a dummy load :)

If S meter reports are to be believed, then I am not often the big signal, am fairly often on-par with other nearby stations, and as fairly often down by an S unit or so.

That is not surprising - the lowly diplole up a half wave or so, is going to be higher by an S unit or more over a vertical.
 
The 25-Foot Untuned Vertical -- 7 Bands  
by KD6RF on October 16, 2012 Mail this to a friend!
pic ----> http://i154.photobucket.com/albums/s257/KnowFear1111/Ant1.jpg
 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by N6BIZ on October 16, 2012 Mail this to a friend!
HI OM ...TU FOR YOUR ANTENNA ARTICLE ... I HAVE TO GO UP ... ABOUT 15 FEET ON THE ROOF IN THE REAR OF THE HOUSE... I CAN ONLY DO 1 RADIAL 25 FEET LONG AND ILL BE FEEDING THE ANTENNA WITH 450 OHM LINE TO A TUNER IN THE SHACK ... U KNOW THE HOA PEOPLE ... HOW DO I DO THE SHORTNER? AND IF I WAS GOING TO DO A 43 FOOTER UR IDEAS ALSO
 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by W8JI on October 17, 2012 Mail this to a friend!
Hi Dave,

I wish eHam had a review comment process in place before posting as a final article. I think it is too polarizing and distracting to do comments AFTER an article is public. Comment after final publication is a bad system.

<<<<by KD6RF on October 16, 2012
The "shortener" is attached to the fence (soldered brass plate). It is just a short mid-loaded 4 ft parasitic element tuned to around 32 MHz, much like a director. In fact there is some asymmetry on 10 Meters, about 1.5 dB worth in the plane which contains the vertical and the "shortener". >>>>

That's much clearer to me. I thought the stub was attached to a ground rod for some reason. :-)

This is the same method used in many antennas, where the stub is on either the feedpoint hot terminal or the shield terminal.

The difference is in phase of the stub, and whether the stub behaves as a transmission line or as a "diversion" for common mode currents. In your case the stub probably acts like a transmission line on the band where it is near 1/4 wave long or multiples of that length.

<<<I found it useful to think of it as a sort of frequency dependent transmission line extension, that raises the feedpoint higher at 10 Meters (therby effectively shortening the antenna), while pretty much being invisible at lower frequencies.>>>

That makes total sense to me now.


<<<I don't place a huge amount of faith in models without verification of real world data, but found it nice that there was very good agreement in impedance, and gave a bit of confidence that twiddling the antenna in the model would at least give qualitative guidance.>>>

I've always found impedance to be close, but efficiency can change contrary to what we might expect by a change in impedance. Still that does not affect anything in this case, because nothing magical or contrary to common sense has been claimed. It is a good down-to earth article.

Thanks for clarifying the connection of the stub wire. I wasn't exactly sure how it connected.

I always wonder why people building 43 foot verticals don't use stubs, but I guess then we would have a bunch of HyGain Hytower verticals or ground mounted AV640's instead of 43 foot Gotham verticals. :-)

73 Tom
 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by NY4D on October 17, 2012 Mail this to a friend!
Dave,

Thanks for updating re the "shortener" as you called it. Now the element and its purpose makes sense to me.

At the previous QTH I was space constrained so I used a similar setup, though monoband on 40, so no "shortener" was needed. 60 feet of welded wire fence was the counterpoise. It just happened to be there. I compared the fence alone to four elevated resonant radials alone and also to the fence and radials tied together. There was no real world discernable difference in signals among the three though I am sure there is a theoretical one. A current choke was used at the feedpoint.

All you HOA and otherwise space restricted hams out there, this is a way to get on the upper HF bands.
 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by N6BIZ on October 17, 2012 Mail this to a friend!
HOW ABOUT AN EASY TO VIEW DIAGRAM OF THIS SETUP FOR ALL OF US APPLIANCE OPERATORS...
 
The 25-Foot Untuned Vertical -- 7 Bands  
by NZ5L on October 17, 2012 Mail this to a friend!
Nice overview.
However, I disagree that a "minimalist" ground system will suffice. In most cases, there will be more attenuation from lossy ground than high SWR up thru 20 Meters. What you may not have considered is that radials at the surface can be significantly shorter than an actual 1/4 wavelength. Even for 80 Meters, a reasonable number of 30' radials will very nearly match the "ideal" 1/4 wave radials, and for higher bands this still holds true. A ham with a smallish lot could lay down 30 or more 20 footers (and remember, they need not be straight) and have a reasonable signal on 40 thru 17 Meters with a simple vertical wire monopole. A simple "L" matcher can sometimes help a worst case SWR and not adversely affect others. It's worth a try, and very simple to experiment with. Anyway, it's all about having fun while learning, so continue the march.
 
The 25-Foot Untuned Vertical -- 7 Bands  
by KD6RF on October 17, 2012 Mail this to a friend!
N6BIZ, here is a sketch of the setup ----> http://i154.photobucket.com/albums/s257/KnowFear1111/ant_diag.jpg

If you depart much from this design, with a roof mount, or scale it up to 50 ft, things will likely shift around a bit, and it will have to be tweeked to be sure it's doing what you want.

If you enjoy doing the design or like to change dimensions around a bit to see what happens, then EZNEC or the like is cool. For me, doing something a bit off the beaten path is what I enjoy most about ham radio.

Not to discourage you from just putting something up and trying it, but odd-ball designs like this can sometimes be tricky, especially with the high VSWR's that the antenna presents to the feed line.



NY4D - I haven't seen a good set of measurements that show a set of short radials that would not be considered "minimalistic" when compared to an elevated full radial system. (I have seen the nice multi-part series of measurements exploring short ground level radial performance, but, if I am not mistaken, there is no comparison done against elevated radials which I suspect are significantly more effective).

Of course, just because I haven't seen it doesn't mean it's not true :)

One note - not sure what you mean by "A simple "L" matcher can sometimes help a worst case SWR and not adversely affect others."

Impedance varies wildly, and VSWR reaches 20+, over the 2 octave bandwidth, so a wide range tuner (whether a set of switched or plug-in L networks, or a more general T-tuner) doesn't just help, it's required to hit all the bands!!!





 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by KD6RF on October 17, 2012 Mail this to a friend!
Oops, last part of post was meant to be addressed to NZ5L...
 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by N6BIZ on October 17, 2012 Mail this to a friend!
TU OM ...
73
 
The 25-Foot Untuned Vertical -- 7 Bands  
by QRPNEW on October 18, 2012 Mail this to a friend!
Can you model the antenna with a 9:1 Unun at the base, thats then fed with the antenna tuner at the end of the feedline?

I have been using various verticals like this with a 9:1
UNUN. They have worked well but relative to something else I dont really know how good they really are.


I got the inspiration from this web page which includes
field strength measurements.

http://g8jnj.webs.com/
 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by KD6RF on October 18, 2012 Mail this to a friend!

Hi QRPNEW – This article is about changing around the length and configuration of the 21.5 or 43 ft vertical in order to pick up a few dB, especially when using mediocre grounds, and not so much about feeding the system.

Sorry, I don’t have much to add when it comes to using ununs and the like. Personally, I don’t care for the idea of purposely introducing lossy components into the system. If you are stuck having a long feedline (more than 100 feet or so), then I would consider some plug-in matching components at the antenna feedpoint (or some accessible location near the feedpoint) in order to knock down the VSWR, thereby reducing feedline loss, before I would start using baluns or ununs on a system that has wildly varying impedances.

I would rather take a walk out into the rain to switch up the matching network than burn up half or more of my power in a lossy system. But that’s just me :)

Or, perhaps NZ5L has come up with a nice simple matching network that mitigates the high VSWR issue at mid frequencies, while not increasing it at the high and low end.
 
The 25-Foot Untuned Vertical -- 7 Bands  
by KB4QAA on October 18, 2012 Mail this to a friend!
The modeling diagrams look very pretty. However I must take exception with the claim that this contraption will perform within a couple dB of a vertical with 50 radials.

It might in two (2)direction, i.e. along the fence alignment. But it is impossible once you move more than a few degrees from that line of direction.
 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by N6BIZ on October 18, 2012 Mail this to a friend!
THE DIMENSIONS OF THE COIL PLEASE ?
 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by KD6RF on October 18, 2012 Mail this to a friend!
Hi KB4QAA – You are quite right that the antenna exhibits a bit of directionality. However, it is far from impossible to have good response “once you move more than a few degrees from that line of direction”.

Not surprisingly, the least pattern distortion is at the lowest frequencies, and models out to less than 1.2 dB up through 20 Meters, with 40 Meters being barley discernable from omni.

Above 20 Meters, things get a bit less omni, with worst case asymmetry of about 2.6 dB at 10 Meters.

I did a bit of testing with the mobile rig, and it is in general agreement with this claim. Now, I only used the S-Meter at convenient points on some local roads, along the fence line direction (E/W), and broadside (S), at about ½ mile distance. These, of course, were only crude measurements, and not worth publishing, but always showed less than an S-Unit difference, with the least amount of difference at the low freqs. So I have fair confidence in regard to the modeled results vs. real-world. Who knows – a well planned formal test may show that it is in fact 2.1 dB of asymmetry on 20 Meters instead of 1.2, but in any case there is much less pattern squishing than you may have suspected.

Remember, this is only a mediocre ground system, whose performance is enhanced by the metallic fence line (and some antenna tricks to coax out a few more dB), and whose whole reason for existence is to provide those with limited space (or those like me who don’t like the idea of a big complex radial system) an option that they may otherwise not have tried!

As N8JI and VK1OD and others have noted, modeled results, especially in regard to real ground, can be off by a bit. But the EZNEC model results, and my cursory S-Meter readings would have to be waaaay wrong if the antenna in fact only had a few degrees of efficient beamwidth.

 
The 25-Foot Untuned Vertical -- 7 Bands  
by KD6RF on October 18, 2012 Mail this to a friend!
Here is another way that I find helpful when thinking about it KB4QAA -

Imagine the 50 elevated radial system - it's not hard to believe that it a near perfect omni pattern.

Now imagine a 10 elevated radial system - ditto, near perfect omni.

Now imagine the 4 elevated radial system, then the 3 elevated system, aka the "ground plane" antenna, that we are all familiar with - they also have very nearly omni patterns. They do not exhibit "beaming" of a few degrees along the radial directions.

Obviously the next step is to imagine the 2 radial system. It shouldn't be hard to believe, given the above, that there is no beaming of a few degrees along the radial (fence) line. While starting to show a bit of directionality, it is still pretty darn near omni.

 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by W5WSS on October 19, 2012 Mail this to a friend!
I have built and been using the 22ft vertical length for about 6 months here at a summer cottage in TN.

The antenna concept is very good and mine has been very gratifying.

.As an alternative to a fence: My elevated vertical starts at exactly 5 ft too

I however, built tuned pairs of wire radials and fanned them downward and opposite each other from the driving feedpoint sheild.

The radial sets are for 40m to 10m and are ground isolated and dead ended to non conductive tent stakes.

When viewed from the side they are longest set top and shortest set bottom as they expand outward and downward from the feed point and attach to the non conductive stakes.

Otherwise your fence exchanges this system.

Rather than using a shortening I incorporate provision for quick changing between the 22ft and 44ft length verticals that takes about 3 minutes. One or the other then operating and pushing against the already in place radial sets.

A compromise could be found by modelers, in the proximity effects of the individual radial sets fanned, but I have not modeled that area of multiband counterpoise systems interactions.

Nice article I thought I would share my findings and add why your design ideas are good.

 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by N6BIZ on October 20, 2012 Mail this to a friend!
COIL DIMENSIONS PLEASE
 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by W4VR on October 20, 2012 Mail this to a friend!
You can tune just about anything with a good remote tuner. I wish I had a remote tuner when I used a Gotham V80 vertical in the early 60's....perhaps I could have worked more then the single station I logged in.
 
The 25-Foot Untuned Vertical -- 7 Bands  
by KD6RF on October 20, 2012 Mail this to a friend!
N6BIZ - Note that I made a boo-boo in the diagram - it should be a 1.5 uH inductor NOT a 2.5 uH.

(I uploaded the corrected diagram to photobucket, but it looks like e-ham has the old version on it's own server...)

The coil I used came out of the junk box, and is 1.5" x 1.5" and a bit more than 7 turns with 1/2 inch lead length connecting it to the guts of a Radio Shack telescoping antenna from an old CB walkie talkie. It look like #18 wire.

You can come up with a size that may be easier for you to construct if you use one of the on-line inductor calculators. I sometimes use this one ----> http://hamwaves.com/antennas/inductance.html

W5WSS - Congrats on your design. It sounds that you, like I, enjoy building and using stuff one actually builds for oneself!

For me, that's the most fun part of the hobby.

 
The 25-Foot Untuned Vertical -- 7 Bands  
by K1LLR on October 20, 2012 Mail this to a friend!
just cant be done with good results..verticles recieve as poorly as they try to transmitt withh any good results unless your running L.L.
 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by W5WSS on October 21, 2012 Mail this to a friend!
W4VR The science of antenna radiation has been comprehended long ago and the tool or, basic building block is the dipole whether vertical or horizontal radiation released into the environment is effected by the earth more or less is a function of many variables but either are equally capable to release the exact same feild strength. when both legs are treated equally then the feild strength is equivalent.

There is a place for the vertical antenna regardless of your opinion.

What represents the second leg of a vertical dipole? A Marconi uses the earth whereas a vertical dipole Can use a second leg split into many parts but still represent the second half. The Earth surface down low effects the horizontal family of antennas worse!

A vertical dipole is as useful as a horizontal dipole.
Because lower frequencies increasingly demand the horizontal dipole to be unpractically higher and higher for radiation objectives.
We see once again that the Earth effects equally;

The place where a vertical does more is found where the horizontal does less vs the Earth surface.
 
The 25-Foot Untuned Vertical -- 7 Bands  
by K2JX on October 24, 2012 Mail this to a friend!

I figured this got to be in a city lot like mine ! But no, look at that wide open space. If I had that I'd put up a 100' tower with wires and Yagi's, then shunt load the tower for 160,75 & 40m. Oh, the possibilities !

I live on a 50' X 150' lot, have a 43' Vertical over 165' of #6 copper radials, 125' of RG-231U coax feeding the antenna through a UNUN 10kw rated. I am pleased with antenna after 2 years of use for DX & casual QSO's, 99% CW. Nice artical & graphics !

Tnx, 73 de K2JX nr NYC
 
The 25-Foot Untuned Vertical -- 7 Bands  
by N3DT on November 23, 2012 Mail this to a friend!
I really don't know why people put up with verticals that need grounds and all the associated losses. All you need to do is make a C-Pole antenna with a current ferrite isolator and the ground issue disappears, you have a vertical with low angle radiation, multiband operation with a tuner and stealth as a side benefit. I have an 80M C-Pole that works on 160-80-40-20-12 and a 60M C-pole that works on 60-30-17-10. No ground rods or wires and great low angle radiation. Look it up, it's too simple.

Dave
N3DT
 
The 25-Foot Untuned Vertical -- 7 Bands  
by AE4YW on November 29, 2012 Mail this to a friend!
WOW! Someone sure did a lot of work to publish this. I mean pictures, graphs, smith charts, lots of text, looks good! And it gets 7 bands, wow!

I thought once about sticking a screwdriver up in a stump, winding a loading coil on a plastic 55 gallon drum and hooking it up with jumper cables. Back a ways in time I did try all kinds of things. Hooked a guywire up once and talked to someone in Kentucky. Told him it was a VEC slopper (volunteer electric coop). I hooked up the metal roofs on my house and garage and made it all the way to Alabama with that one.

Ever wonder why there are so many antenna designs? Seems everyone has an idea how to work multiple bands on one wire. Now here is wisdom, write this down, throw away your antenna tuner!!!!! The sooner you do the sooner you will have to create a resonate/tuned antenna for each of the bands you want to work. Then there will be flowers and hummingbirds everywhere LOL! Keep the tuner and QRM and low power and frustration will be yours forever. Of course there is the stump, screwdriver, 55 gallon drum and jumper cables................
 
RE: The 25-Foot Untuned Vertical -- 7 Bands  
by KD6RF on December 3, 2012 Mail this to a friend!
Hi N3DT,

The C-pole is a cool antenna. But I wanted one that cover as many bands as possible with a single antenna. And of course, was dirt simple to build.

I have considered building one or two C-Poles as portables and drag them to a hill-top, especially for 20M, where the mobile antenna starts crapping out - some day I will get the time to do so!

One thing to be aware of however, Dave... Just because it is not physically connected to ground, doesn't mean ground losses disappear.

There is no stop sign under the C-Pole saying "Halt! E and H fields may go this far and no farther!"

Current is still induced in the ground, and the earth worms still thank us for keeping them warm.

Modeling shows this - the C-Pole comes in at a few tenths of a dB better than the fence-ground-vertical, and a few dB worse than a full blown radial system, especially an elevated radial system. And, of course, high-angle lobing and directionality can kick in when using a large C-Pole on the higher bands, which can really knock down lower angle radiation.

 
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