Vertical Sleeved Dipole How-To

[HomerBB]

There has been some repeated interest in homebrewing a suitable dipole for vertical use on several forums and numerous threads. I decided to put this info up so a forum seach could take them directly to this method of getting on the air with an easy to make, pole mountable, rigid version of the vertical dipole.
I hope it helps.

If you want a vertical dipole then:

1. get two 1' pieces of PVC with sufficient diameter to insert an aluminum tube into.

2. cut the end off of a coax feedline and separate the braid from the center for about two inches.

3. put this prepared end of the coax all the way through one of the 1' PVC nipples

4. cut both of the tubes of aluminum to 8' 7" length.

5. push the prepared end of the coax all the way through one of the aluminum tubes.

6. this results in the PVC nipple and one of the tubes sharing the coax through them, so now insert the aluminum tube into the PVC nipple for at least six inches and secure them to each other with a short self-drilling screw.

7. take the second PVC nipple and drill into the side of it exactly in the middle a 1/4" hole, or one large enough to feed the coax through.

8. push the coax into one end of the PVC nipple and pull it out of the nipple through the hole you drilled into the side.
9. Push the nipple onto the Aluminum tube 5.5" deep.

10. You should now see your prepared end of the coax sticking out the hole in the side of the PVC nipple. Press the other aluminum tube into the PVC nipple for a distance of 5.5". Secure both tubes with short self-drilling screws.

11. Now take the prepared end of the coax that is sticking out through the center PVC nipple and fasten them into the ends of the two aluminum tubes with short self-drilling screws through the center PVC separator/insulator.

12. Take either silicone, tape, or heat shrink and place it on/over the coax to dipole connection for weather-proofing. Optionally you may cap the end of the dipole which has no PVC insulator on it. This is the top.

13. Where the coax comes out of the bottom tube/PVC insulator make a coax choke of 4" - 5" diameter x 5/6 wraps.

The bottom PVC insulator provide a means of mounting the dipole to a mast. If more sturdy mounting than the PVC provides is needed you can wrap the PVC with fiberglass, or use an old fiberglass shovel handle instead. I've done both. If the dipole needs tuning as it may be too long by a little due to its diameter trim from both ends of the aluminum tubes as you would any wire dipole.

 

[Robb]

XLNT Homer!


For your outstanding work on so many different antennas and how to do them right, you are the undeniable winner of the Tim Allen/Tool guy award!


http://www.youtube.com/watch?v=6XUg5cfwilI


Keep up the great work, Homer!

 

[HomerBB]

LOL

 

[Robb]

BTW - did you get any signal reports with it yet?

Also - what is the estimated cost of materials and time for the project?

 

[Black_Bart]

buy one of these and you can make a dipole out of a pair of mobile antennas, i made a horizontal out of two 102 inch steel whips and they sag just a little bit making it almost an inverted V but just a little wide to call it a V, i am sure it would work just as well vertically

MFJ Enterprises Inc.

 

[mackmobile43]

buy one of these and you can make a dipole out of a pair of mobile antennas, i made a horizontal out of two 102 inch steel whips and they sag just a little bit making it almost an inverted V but just a little wide to call it a V, i am sure it would work just as well vertically

MFJ Enterprises Inc.

try sliding your mount down on the pole and tie a piece of non-conductive cord to the whip ends for support and to the top of the pole for a better TOP.

Nice job HOMERBB

 

[HomerBB]

@Robb -
I do not have the antenna in the air, now, although the second photo is still up across town. That one I did for an old fellow who lacked the funds for an antenna. Signal from him is as good at the distance from me as any other that distance, however, the old fellow doesn't get on the air very often. It is a dipole, so performance is the same as any dipole, the exception being that its vertical polarity gives it advantage for local vertical radio traffic which results in increased signal TX/RX locally over the horizontal dipole.

Cost for the antenna can vary based on whether one already has some tubing lying around, or has to buy it. An off-hand estimate would be perhaps < $15.

The one in the second lower photo differs in that the lower tube is a joint of 1/2" EMT which prices out at < $2. The upper part is a yard sale piece of aluminum tubing mated with one ski pole for a combined cost of $1.50. Instead of PVC insulators, I used a fence picket from the cull lumber at The Home Depot which cost 51¢. Add to that the clamps holding the tubes to the boards maybe that cost me a total of $8.50 total cost.

Coax is an assumed cost for any antenna installation.

@Black_Bart -
It is a fact that a dipole can be made from the two mobile sticks. I've done that , too. What is different about this model is it can be mounted vertically in exactly the same manner as the A99 or any other vertical, and that by running the feedline up through the lower tube the issue of feedline needing to be routed straight away horizontally from the vertically mounted dipole is resolved. It doesn't exist.
I have hung this kind of antenna from a tree several times, too, by drilling a hole through the top tube and stringing it up via tie off.

 

[Bob701]

Thanks for sharing that Homer. Neat idea.

 

[HomerBB]

No Problem:

Due to questions on various forums I am posting this re the dipole.

The one in the above photos over the Yagi was mine, the other I made for a fellow across town who lacked funds for a decent antenna and was using a mobile mag-mount on a window air conditioner.

Both of them performed as well as a dipole usually does, except better for local because this design is vertical as opposed to horizontal.
As we know, dipoles have no gain making them the antenna against which gain is compared for other antennas. So the beauty of this antenna is that once the materials are laying on the floor/bench in front of you it can be on the air talking within 1/2 hour. Being a tubing dipole it has the rigidity to be mounted from the bottom as other verticals are, and have greater bandwidth due to the greater diameter of the tubes over wire dipoles on the same band.

Other than comparing gain to antennas such as .625/.64, or beam antennas, I'd rate this antenna as a homebrew a 10 on a scale of 1 to 10.

materials availability ------- 10 (any hardware store has these materials)
ease of construction ------- 10 (tools - hacksaw, drill, wire strippers, tape)
ability to mount ------------ 10 (u-clamps to mast pole on the bottom insulator)
meets standards of design -- 10 ( performance exceeds wire dipole bandwidth, and permits local vertical communication)
cost ----------------------- 10 (< $15 US dollars)

It can be seen that the slimness of this vertical design does not offend the skyline when picky spouses and neighbors are to be considered.

Additionally the antenna is a great portable design, too. Simply removing the top tube from the center insulator for transporting reduces it's length by half. It is very lightweight, but strong, and will endure years of use.

It a winner on virtually every level.

 

[Marconi]

Very good design Homer, and thanks for the construction details.

I think most CB'rs would probably claim the 1/2 wave is just a little better than a dummy load, but not me. I see similar results with my 1/2 waves...even when the match is not so good.

 

[HomerBB]

We all know that an antenna is subject to performance variables inherent to the location it's in. Nevertheless, whatever a dipole will do at a given place this one does very well.

 

[HomerBB]

Some folks had asked me to add photos of an assembly step-by-step. Here you go.

If you want a vertical dipole then:

1. get two 1' pieces of PVC with sufficient diameter to insert an aluminum tube into. (Because my materials for this dipole require I have a taper on each end I am making the lower insulator more than 1' long. The center one is actually 13" but I used it anyway.)

2. cut the end off of a coax feedline and separate the braid from the center for about two inches.

3. put this prepared end of the coax all the way through one of the 1' PVC nipples

4. cut both of the tubes of aluminum to 8' 7" length.

5. push the prepared end of the coax all the way through one of the aluminum tubes.

6. this results in the PVC nipple and one of the tubes sharing the coax through them, so now insert the aluminum tube into the PVC nipple for at least six inches and secure them to each other with a short self-drilling screw.

7. take the second PVC nipple and drill into the side of it exactly in the middle a 1/4" hole, or one large enough to feed

the coax through.

8. push the coax into one end of the PVC nipple and pull it out of the nipple through the hole you drilled into the side.

9. Push the nipple onto the Aluminum tube 5.5" deep (because I cut the center PVC nipple 13", I put the aluminum tubes in 6"), leaving a 1" space in the center.

10. You should now see your prepared end of the coax sticking out the hole in the side of the PVC nipple. Press the other

aluminum tube into the PVC nipple for a distance of 5.5". Secure both tubes with short self-drilling screws.

11. Now take the prepared end of the coax that is sticking out through the center PVC nipple and fasten them into the ends

of the two aluminum tubes with short self-drilling screws through the center PVC separator/insulator.

12. Take either silicone, tape, or heat shrink and place it on/over the coax to dipole connection for weather-proofing.

Optionally you may cap the end of the dipole which has no PVC insulator on it. This is the top.

13. Where the coax comes out of the bottom tube/PVC insulator make a coax choke of 4" - 5" diameter x 5/6 wraps ( I haven't

mounted this in the air yet, so step 13 will have to wait).

The bottom PVC insulator provide a means of mounting the dipole to a mast. If more sturdy mounting than the PVC provides is

needed you can wrap the PVC with fiberglass, or use an old fiberglass shovel handle instead. I've done both. If the dipole

needs tuning as it may be too long by a little due to its diameter trim from both ends of the aluminum tubes as you would

any wire dipole.

 

[HomerBB]

Adding an expansion of the info in step 11.

Notice in the photos below how the coax is pulled through the hole in the side-center of the center dipole insulator.
The dipole tubes (black in this demo photo) are pushed into the center insulator only as far as the marks on the nipple. There are four screws holding the dipole together. Two of these are strictly to hold the 3 tubes together as a unit, but the two dipole elements remain separated. The second set of screws are in each of the dipole tubes with the center wire of the coax going to the upper dipole tube, and the braid going to the lower dipole tube.*

*Note: All materials used in this post are for demo purposes only. No animals were harmed in the process, but would have been had they been in the shack and behaving viciously.

 

[BammBamm]

Homer if you keep designing antennas solarcon is going to start contacting you for ideas!:tongue:

 

[Robb]

Some questions do come up here:

*When erecting this vertical dipole, how far away from the end of this dipole should this dipole need to be from any metal? Since the voltage max of a dipole is at the ends; then it will need to be a given distance away from any metal to keep it from 'capacitive detuning' of the same dipole.

*What kind of dielectric material would you prefer to keep it strong and insulate it from the dipole and the mounting mast?

*Is there any practical ways that you can demonstrate to make this dipole rotatable from the vertical polarization to the horizontal polarization?

*For that matter, is there a practical way to make it rotatable in a 360 degrees when in the horizontal polarization?

Nice work, Homer!