OH NO, Another Antenna Question

[mcjim555]

I'm contemplating building a J-Pole, but I have a couple of questions.

1. Most of the J-Pole web pages say to use 1/2" copper tubing, but the J-Pole I'm building is going to be 26 Feet tall so what diameter would you guys suggest and is copper tubing strong enough ?

2. If the short quarter wavelength stub is used to tune the antenna, then how do you tune it if you are using copper tubing soldered together. Is it just a matter of trimming the short quarter wavelength stub to the resonant frequency or is there a different way to tune this antenna since it will be soldered together ?
Thanks and 73 Jim http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif

[AG3Y]

Sounds to me like you are going for something on 10 meters, right ? Tell us more why you are going this route? There are far simpler ways to build a 10 meter vertical, and you can even build a design with some gain, without having to resort to that design.

Have you checked the ARRL antenna handbook to see what else might be of a more practical possiblility ?

To answer your question, I would NOT use copper tubing for that antenna. Aluminum is far more suitable and less expensive in the sizes you would need to pursue this.

That also takes care of question #2, because you obviously are not going to be soldering aluminum, but rather using telescoping sections. And yes, tuning an antenna of that nature is a combination of adjusting the length of the short section, as well as the attachment points of the coax cable center and shield .

But again, for the amount of trouble and expense you are going to have putting together something that tall and ungainly , you could have a decent 3 element beam that would work circles around a vertical ! Think about it !

73, Jim

[K9STH]

Actually most "J-Pole" designs do NOT use copper tubing but use copper pipe. There is a BIG difference in both weight and strength between copper tubing and copper pipe.

Copper pipe weighs less than the same diameter copper tubing but is MUCH more rigid and comes in straight sections normally 10 feet long. There are 3 different "grades" of copper pipe: red, blue, and green. Red is the softest (has less mechanical strength and the thinnest thickness of the copper used in manufacture). Blue is a "medium" strength and is in the "middle" in terms of both strength and thickness of the wall of the material. Green is the strongest of the copper pipes, has the thickest wall, and has the most weight of the pipes.

Green is used primarily for commercial air conditioning systems and is pretty hard to obtain except from an industrial supply company. Red and blue are stocked by home improvement centers like Lowe's and Home Depot. You want to pay the extra dollar, or so, and get the blue. The easiest way to tell what type you have is that all of the information on the pipe is printed in ink that gives the manufacturer, type number, etc. and the color of the ink is the "grade". That is, if the information is printed in blue ink then the pipe is of "blue" quality. If the information is printed in red ink then the pipe is of "red" quality. If the information is printed in green ink then the pipe is of "green" quality.

The sections of pipe are going to be straight whereas copper tubing comes in rolls. Copper tubing is much heavier in terms of weight but does NOT have any real strength when used to support even its own weight. Copper pipe, on the other hand is VERY difficult to bend but can support its own weight plus the weight of other sections very well.

You can join the lengths of pipe with couplings that are sold at the home improvement center. Make sure and get some paste type flux to use when you solder the commections together. Just wipe the flux around where you want to solder, heat with a propane torch, touch solder to the pipe (it will "tin" almost immediately), then put the connector on the pipe and heat for a few seconds. The connection will be excellent.

The two sizes of pipe that are most common at home improvement centers is 1/2 inch and 3/4 inch diameter. For something 26 feet long I would recommend the 3/4 inch diameter. But, the 1/2 inch can support its own weight in most cases especially if you use the "blue" or "green" type of pipe.

A "J-Pole" is tuned by moving the coaxial cable connections up and down and not by varying the length of the pipe. Clamp both the shield and center conductor in place where the instructions say to attach them. Check the reflected power (or SWR depending on whether or not you are using a wattmeter or SWR bridge). If it is not "good", then move both the center conductor and the shield attachment point a VERY small amount (and in the same direction for both). Check the reflected power / SWR again. If the reading is decreasing then move the connection a VERY small amount in the same direction as before. If the reading is increasing, then move the connection the other way a VERY small amount. Keep doing this until the reading "bottoms out" and starts to increase. Go back to the point just previous and make the measurement. This will be the place to permanently attach the cable.

Again, you want to use copper PIPE and NOT copper tubing.

Glen, K9STH

[mcjim555]

Hey there Jim, I guess it doesn't have to be a J-Pole, but I would like to build a verticle antenna with some gain. I just thought about the J-Pole because I'm trying to learn as much about antennas and theory as I can, so I thought I might try it. If you have any suggestions about what would be a better bet for me then I'm listing. I'm not going to go with a beam right now, because the weather up here will not cooperate and I will need to get a tower and rotor also which won't happen until next spring. Thanks again and 73 Jim http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif

[K9STH]

If you want to make a vertical dipole instead of a "J-Pole" go to either of my websites. Near the bottom is a link that tells how to make either a 6 meter or 10 meter vertical dipole. The URLs of the websites are

http://home.comcast.net/~zcomco

or

http://home.comcast.net/~k9sth

Glen, K9STH

[N5LRZ]

@ AG3Y....

10 meters, close but no cigar. Remember that a J Pole is 3 quarter wave lenghts long. IF the length is 26 feet long then that would make a quarter wave length 8.666 feet. If the antenna was being used for 10 meters the length of a quarter wave would be barely over 8 feet in the lower end of the 10 Meter band.

This antenna is being made for CB not 10 meters. Hmmm if I do my quarter wave length properly the central core frequency in ref to measurements for 26 feet is 27.209 (234/27.209 times 3) which would be in the CB Band. That would be CB channel 20.

Well at least its not in the freeband section.

Well at any rate I hope he does NOT use matal guy wires on the vertical because the use of metal guy wires would act as a cap top loading and possibly screw up the load on the antenna. I hope he uses NON metalic nylon rope or some other non metalic guy materials.



R Arceneaux
N5LRZ

[N5LRZ]

@ 555

If you are making the antenna for the band which I suspect you are you need to know a few facts about the Solar Cycle. There is something called the 11 year solar cycle. Every 11 years the number of sun spots goes up and down in an 11 year cycle. These sun spots charge up the atmosphere and make skip possible. The fewer the sun spots the worse the skip will be.

Right now we are in the last couple of years of a bottiming out process in re to the number of solar storms aka sun spots. IF the cycle is on target skip will get worse on the 27 and 28 Mhz territory for the next TWO years. THEN it will slowly rise meaning that for the NEXT 4 to 6 years look for terrible skip on the higher frequencies.

Which is my way of saying that its a nice thought to experiment on the J Pole as an HF antenna but just not the right time in the solar cycle to be practical.

Which is why a General Class or higher license for the Amateur Bands is so good to have. When the higher frequencies bottom out the lower frequencies, which need far less charging to kick in skip, start to become workable.

IF IF IF you do not have a General Class License or higher may I suggest that you study for the license and take the tests. At least during the bad years you will be able to use 40, 80 and even 160.

At least you will have some place where there will be some skip to talk to.

R Arceneaux
N5LRZ

[mcjim555]

Quote[/b] (N5LRZ @ Nov. 13 2005,20:35)]@ AG3Y....

10 meters, close but no cigar. #Remember that a J Pole is 3 quarter wave lenghts long. #IF the length is 26 feet long then that would make a quarter wave length 8.666 feet. #If the antenna was being used for 10 meters the length of a quarter wave would be barely over 8 feet in the lower end of the 10 Meter band. #

This antenna is being made for CB not 10 meters. # Hmmm if I do my quarter wave length properly the central core frequency in ref to measurements for 26 feet is 27.209 (234/27.209 times 3) which would be in the CB Band. #That would be CB channel 20.

Well at least its not in the freeband section.

Well at any rate I hope he does NOT use matal guy wires on the vertical because the use of metal guy wires would act as a cap top loading and possibly screw up the load on the antenna. # I hope he uses NON metalic nylon rope or some other non metalic guy materials.



R Arceneaux
N5LRZ
LRZ you are correct, it's for the Dreaded CB-Band, but I'm studying for my ham ticket. I really have no desire to talk on the VHF-UHF spectrum, so I'm waiting to take the all test including the code so that I can have HF Priveleges. As I had stated I'm just trying to learn as much as I possibly can to put my own antennas together and also to prepare me for helping out at ham club field days and such. 73 LRZ and others. Jim #http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif

[mcjim555]

PS: I am aware of the 11 year solar cycle that's why I'm interested in a verticle antenna with some gain, because I'm trying to talk local long distance or ground waves if that's the proper term. I live in Middlebury Indiana, Northern part of the state (Michigan Border) in the central part of the state. I can hear alot of stations on my small quarter wave groundplane antenna, but I'm not able to talk to alot of them. 73 Jim # #http://www.qrz.com/iB_html/non-cgi/emoticons/sad.gif # #http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

[AG3Y]

I was just taking a wild stab in the dark. Of course you are right about the dimensions, and I can see no harm in his trying to build his own antenna for 11 meters. ( I honestly could not remember if the long section of the J-pole was 3/4 wavelength, or some odd fraction like 5/8s , which is why I guessed 10 meters ! ) The only J-poles I have ever built have been for 2 meters, and they have worked quite well, but putting one on the HF bands would be another matter entirely !


Jim, I applaud your efforts, and it does appear to me that you are heading in the right direction toward a ham radio hobby!

I would strongly suggest that you find a local club and get in with the guys as soon as you can. You might even be able to get involved in some building projects that the club is undertaking. Some clubs go year-round in their preparations for Field Day and other emergency-type operations, and you don't have to have a license to assist in that kind of off the air activity! In fact, you could even get some first-hand experience of listening to some actual net operations, etc. by looking over the shoulder of some licensed operator as he/she conducts some on-the-air activity as part of the clubs agenda.

There is a world out there waiting for you! Good luck, and see you on the air soon ! 73, Jim

[wb6bcn]

Instead of a copper cactus Jpole, why not a Zepp. It amounts to the same thing, a 1/4 wave matching section and a 1/2 wave radiator. With the Zepp there is no tricky hunting for the sweet spot as in the copper cactus.

If you want details on the Zepp, drop me an email, or post a PM.

[K8ERV]

Why does anyone live in Indiana?

TOM K8ERV Montrose Colo

[N5LRZ]

@ wb6bcn

Just curious. There are two versions of the Zep Antenna.

There is the "Modern" version which resembles a dipole that is fed with a 4:1 balun.

Then there is the extended Zep which is the longer version and nothing more than an Off Center Fed Dipole aka OCF Dipole.

And there is the "Original" Zep which is a quarter wave length of ladder line or coax at a desired frequency using the center conductor of coax or one of the ladder line conductors feeding in an end fed configuration a half wave of copper wire.

Just curious, which one were you making reference to.

R Arceneaux
N5LRZ

[K9STH]

I believe that everyone needs to go back and take a look at what is really the Zepp antenna (the original design that was used by the Germans for trailing wire antennas on the Zepplin airships).

The original Zepp is a half-wave (or powers of 2 multiples of a half-wave) that is end fed with balanced line that is a quarter-wave long at the lowest frequency. One side of the balanced line is connected to the antenna and the other side goes nowhere (well it is supported by an insulator but there is no connection to that end of the line).

There have been all sorts of designs stemming from the original Zepp that are now called Zepp antennas. However, the original design still works VERY well for single band and for bands that lie on harmonics that are powers of 2. For example, a Zepp that is approximately 270 feet long (half-wave at 160 meters) works very well on 80 meters, 40 meters, 20 meters, and 10 meters. But, it doesn't work very well at all on 15 meters. The 15 meter band is 12 times the 160 meter frequency which is not a power of 2.

In fact, as the signal wavelength decreases the antenna starts exhibiting some gain. But, the pattern of the radiation can get "very interesting" as the signal frequency increases and the wavelength decreases.

The best wire antenna that I have ever had was a 270 foot long Zepp that I put up in December of 1959. Since I had a 2 element yagi for 15 meters I didn't need peformance on that band. The antenna was still up when my mother sold the property in the late 1980s.

The thing about a Zepp antenna is that it is more horizontally polarized than vertically polarized. However, the feedline definitely radiates and the alignment of the feedline will determine just how much of the radiation is in the vertical plane.

Glen, K9STH

[AG3Y]

Glen I've held the opinion for a long time regarding wire antennas, that the more wire you can put up, and the higher up you can put it, the better the antenna will perform ! ! ! http://www.qrz.com/iB_html/non-cgi/emoticons/cool.gif

73, Jim

[K9STH]

There is another "factor" that must be considered when comparing antennas and that is the severity of the weather when the antenna was installed. Frankly, the worse the weather the better the antenna is going to perform.

The Zepp that I put up in 1959 was put up to get in on a 160 meter contest that I came across. To get enough wire I had to unwind several television power transformers (I used the wire from the filament windings) and soldered the wire together until I got 270 feet. Then I went out in the yard where there was about 3 feet of snow on the ground and got the wire up on a "T" pole, a wild cherry tree, and a 20 foot telephone pole that K9BPV had given me and my father and I installed the pole in the back yard. The "near" end of the antenna was at the house. Did I mention that this all took place about 3 AM, the wind was blowing over 20 miles per hour, and snow was coming down at about 6 inches per hour! My parents and sister were sound asleep and had no idea that I was out in the blizzard.

The things one does before he is old enough to get a driver's license!

Glen, K9STH

[KB7UXE]

first off, what frequency are you going to use it on?
1/2 " tubing works well on 2m and up,
3/4 or 1" FOR 6M
The legnth becomes prohibitive any lower than 6m.
Also to adjust the frequency you adjust the connection poit thats between the long and short parts of the j-pole..
E-mail me, I can send you programs on building j-poles.
Dan kb7uxe.
p.s. Tom, behave yourself...
Folks have to live somewhere,
even if it IS indiana...

http://www.qrz.com/iB_html/non-cgi/emoticons/wink.gif

[mcjim555]

Thanks Guys for the replies, I only thought about building the J-Pole because it seemed interesting. BUT if there is another antenna (verticle) that has decent gain and isn't to difficult to build and is fairly inexpensive, I'm all ears. 73 Jim http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

PS: I thought about either a 5/8 or 3/4 wave antenna (homemade), if that helps for the info that I'm looking for.

[KB7UXE]

WHAT FREQUENCY ARE YOU TRYING TO OPERATE ON?http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif???/

[W7LPN]

http://www.hamuniverse.com/antennas.html

Look this antenna site over.

[N7DSW]

If you must have a 10m vertical, most of the 11meter colinear antennaes can be easily tuned to 10 m. I guess nowadays most are fiberglass with tuning rings. If you go to #a cb site that sells the old astroplane or starduster, you can get a good vertical for $40.00-$90.00 -this includes all the mounting hardware, if you don't like it, you've got plenty of aluminium to work with. 73

[mcjim555]

Quote[/b] (kb7uxe @ Nov. 14 2005,21:02)]WHAT FREQUENCY ARE YOU TRYING TO OPERATE ON?http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif???/
The DREADED 11-meter band, until I get my ham ticket. http://www.qrz.com/iB_html/non-cgi/emoticons/sad.gif I'm trying to learn. 73 Jim http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

[KB7UXE]

ok, the antron 99 is a great light weight, durable antenna.
And doesn't cost much.
Unless you want to build a horzontal dipole (?)
234/Frequency=legnth each side in feet, X12=legnth in inches each side.
234/27.125=8.627 X 12= 103.24 inches each side.
But wanting to become a ham operator, I'm sure you already know this.. http://www.qrz.com/iB_html/non-cgi/emoticons/wink.gif

While vertical works well when operating in close proxcimity, ( relitive to frequency) signals tend to lay over and become horzontal as they travel around the earth. sooo, the cool dipole you make for 10m will also make a nice recieving antenna for almost anywhere else your hf will recieve.
so if you want to listen to W1AW send slow code on 3.7mhz or where ever, it will work just fine.

[mcjim555]

Thanks UXE, I've used a horizontal dipole before, made out of aluminum tubing (pipe), it worked pretty well. As far as the Antron 99, nothing against it personally, but I prefer to build my own antenna rather than buy one. Thanks for all of the responses Guys and 73. Jim http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

[N4ZYV]

Glen, isn't 12 just 6X2? ;)

[mcjim555]

Quote[/b] (N4ZYV @ Nov. 19 2005,23:44)]Glen, isn't 12 just 6X2? ;)
You need to ask Glen ? ? ? # http://www.qrz.com/iB_html/non-cgi/emoticons/laugh.gif # #http://www.qrz.com/iB_html/non-cgi/emoticons/laugh.gif # #http://www.qrz.com/iB_html/non-cgi/emoticons/laugh.gif