That’s not the point though. If we were to cut off the connector we would surely still see a spark from center conductor to shield. If the cable were near station ground I would expect a spark jump. That large a charge has to go somewhere.

The point is a wire, any wire, with wind blowing on it will build a static charge. We should keep this in mind as we design our antenna systems. Including a DC path to ground is prudent.

I cannot imagine a more teachable YouTube moment. Thanks to the poster for making this video available.

Here is a link to a very old video which explains quite nicely what and how static charge occurs…

http://video.google.com/videoplay?docid=2306375174608358801&hl=en#

73

1. Crimp on connectors have been the norm in industry since at least the 1970s. I’m just ashamed it took me so long to figure this out.

They have just two antennas: a two meter omni and a ladder line fed 135 foot dipole. The dipole is inverted V style atop 12 sections of 48 inch aluminum military mast. The top of the antenna is about 54 feet AGL. Coupled with a good balanced tuner, this thing can work quite well on most of the bands.

The first contact from Virginia was with Japan on 20 meters phone. Not too shabby for such a simple antenna.

Tomorrow we will give it the big test. I know it will work fine because it has already proven its worth during many field days.

If the only antenna you have it a ladder line fed dipole, put it up and go for it.

“Why don’t hams like vertical dipole antennas.

See:

http://i31.tinypic.com/160udqb.gif

Elevated Vertical Dipole

Best regards.
Tom
KE6YNH, 73
San Diego, CA

“With no real models for comparison, it is difficult to compare patterns for each antenna. I would suspect that the J-Pole would not have an omni-directional pattern and would therefore produce a lobe or lobes giving gain in some directions”

Really?

Larry Cebik’s antenna model collection contains hundreds of antennas to examine with NEC or EZNEC and the J-Pole is no exception. However, I did not find a coaxial antenna in his models. So I examined the original patent for the Coaxial Dipole antenna and found it was originally composed of several elements running parallel to the coax to provide the bottom half of the dipole. Great. The models for the J-Pole, the coaxial dipole and a reference typical monopole with 45 degree radials are shown below…

A J Pole, Monopole and Coaxial Dipole modeled in EZNEC

All three examples are simulated with their feed points at 300 inches above ground. The J-Pole enjoys a height advantage for obvious reasons. This advantage become more pronounced at lower elevations since the J-Pole’s height delta is a larger percentage of height above ground the lower the overall height is.

Height increases gain for all three antennas as the ground reflection begins to focus the horizon bound energy. No real surprise there. It is the relative gain patterns we really care about here. Here it is for Azimuth at an elevation about 3.5 degrees…

Azimuth pattern for Jpole, Monopole and Coaxial Dipole

Indeed, you can see the J-Pole’s lack of perfect symmetry results in a slight benefit in certain directions as correctly assumed by the ARES article author. However, the difference is not very significant at less than 3 dB. Also, there are no lobes of gain or loss, in azimuth, like the author theorizes. Lobes do exist for elevation for all three antennas.

Here is a comparison of elevation…

J-Pole, Monopole and Coaxial Dipole EZNEC Elevation

The J-Pole enjoys the most gain at around 6 dBi with the other two antennas pretty close to this value. Again, all three antenna’s gain is very dependent on the height above ground. Thus, the J-Pole always has a slight advantage. Otherwise, the J-Pole is just a half-wave radiator like the coaxial dipole with a slight height advantage.

What are we to make of all this? Well, don’t listen to anyone who tells you one antenna is dramatically superior in performance to another. In the end, they all, more of less, behave like a half-wave radiator and all are a little better than a 1/4 wave monopole over horizontal radials.

The Monopole is the one that bests matches to 50 ohm coax thanks to the angled radials. The coaxial dipole simulates to around 80 ohms impedance which is close to the 72 ohm half-wave value. The J-Pole feed is, indeed, a bit complicated, but matches 50 ohms very well.

So put performance issues aside and concentrate only on the mechanical issues when selecting your next VHF antenna.

Also, you now know better if someone tells you there are no real models for comparison. Simulation has its limits, but is an excellent first step. You can rest assured an antenna invented in the 1930s has been modeled at least once.

Well, to be honest you may well have just as much success with a simple horizontal dipole strung up.

Dipoles are pretty easy to build and don’t cost too much if you would rather purchase one from Alpha-Delta or the Wireman.

However, if you…

• don’t have trees to support your dipole
• already have a dipole, but are interested in seeing if a vertical provides more performance
• have no antenna, but lots of property to try something new
• just want to try something different

…then this simple vertical antenna is for you.

The description on its construction are contained within the pages of…

It is nothing more than several sections of copper plumbing pipe available at any hardware outlet such as Home Depot, Lowes, etc.

The key to any practical ground mounted vertical antenna is radials, radials and more radials. I choose the radial concentrator plate from DX Engineering to organize my radial attachments. In my case each radial is 33 feet long, but since this is ground mounted, the radials are not tuned which means the lengths are not super critical.

I buried the coax between the house and the antenna.

As you can see…

16 foot vertical antenna over radial wires

…this antenna has a simple appearance. However, it works quite well on 20, 17 and 15 meters. I have a few 10 meter contacts too, but this is arguably the wrong band for an antenna cut for 20 meters.

Soon I will be putting up a dipole too since I actually do have a few trees of modest height. I am considering the Alpha-Delta DX-CC as a friend of mine has a large log from his. Plus, this will get me on 40 and 80 meters which is, at this point in the solar cycle, a good place to operate.

When I have both antennas I will do some simple AB comparisons asking:

• Does the vertical receive more noise as everyone suggests it might?
• Does the vertical provide better low angle performance?
• Does either antenna provide a benefit for certain bands and distances?
• Is a replacement vertical radiator such as the continuously tunable SteppIR BigIR vertical or the “tuner-required” 43 foot radiator several companies are selling something worth considering?
• Assuming I get a vertical with more bands along with the dipole DX-CC am I done with antennas for my QTH?

One of the things I love about ham radio is exactly these kind of choices.

Even though my radials are good and plenty, I realize the low angle performance is more reliant on the local soil conditions up to many wavelengths away from the antenna rather than anything I do with my radials. Still radials are there to ensure your antenna efficiency is good so you still should have plenty. Look up the excellent details on Cebik’s web site for more information before you try to understand what radials do for vertical antennas.

If you desire to try a vertical antenna, consider this simple copper pipe version. It is cheap, but does require quite a bit of radial wire. However, if you like what you get with your vertical antenna and want to upgrade to something better, the investment in your radial system will translate right over to your new antenna… and that antenna will love you for it.

UPDATE 2009:
I made my first, and so far only, Phone contact with Australia using this antenna on 20 meters. I was thrilled. This suggests simple antennas do work. However, I do admit the quad array of 20 meter beams used by the Aussie were the significant factor in our QSO