My Experiment in Building a Vertical Dipole Antenna

Introduction: My Experiment in Building a Vertical Dipole Antenna

About: Amature radio operator - general class, preacher, handyman, Dad, husband. Amateur Call sign KF5YKO GMRS Call sign WQWJ296

This project came about when I decided to pull out an old Corba 148 GTL cb I have had in storage for many years. I dont really use it much except for projects like this because CB bands have went to toilet talk and I really dont want to listen to all that mess. But I'm getting ready (saving up) to get a 10 meter ham radio and will be needing a base antenna for it. But my old CB base antenna I had is long gone and I had always wanted to see how a vertical dipole antenna would work. Since 10 meters and cb (sometimes refered as 11meter) are so close in bandwidth often a cb antenna can be tuned for 10 meter. So I checked out vertical dipoles for cb and just couldn't bring myself to pay that much for a manufactured one. So what to do? Simple answer! - Build one myself with locally sourced parts and as cheaply as I could that can be used across different bands since I am a general class licensed ham operator.

Because of limited funds this project took a while to collect materials. Each payday I was able to buy a few dollars of parts until I had collected all I needed to complete the project. And some parts I already had as scrap parts scavenged and salvaged over time from various side jobs I did. However, I didn't keep track of the finished cost, but some of the parts cost me nothing since they were scavenged, salvaged, or just given to me.

Note: This is my first Instructable. Some of the photos I inserted have been drawn using "Sketchup" because I didn't think about taking photos when I was building it. I get tunnel vision when I do a project. So I made drawings to help illustrate the process. I hope they make sense.

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Step 1: Research, Research and More Research.

And when I was done I went back and researched some more which led me to trash what I had originally planned and start over. I have listed two sites which helped me the most in my research to build this antenna so to give proper credit:

http://195.84.101.101/~goranl/building/aircore_bal... I used the info on his 1:1 Balun design.

http://www.amateurradio.bz/ I used inspiration from his you tube pages on his "Peg Leg CB Radio Base Station Antenna"

Step 2: Gather Materials and Tools

Materials

  1. 1 - 3/8" x 10' hard copper pipe (Cut it in half to make 2 - 5ft radials)
  2. 1 - 1/2" x 10' hard copper pipe (Cut it in half to make 2 - 5ft radials)
  3. 2 - 3/8" copper caps
  4. 2 - 1/2" copper male adapters14 awg solid core, insulated wire
  5. 1 - 1/2" x 5" peice of PVC pipe
  6. 2 - 1/2" x 3/4" PVC reducer
  7. 2 - hose clamps
  8. 1 - 3/4" x 3/4" x 3/4" metal (NOT PVC) conduit body T with cover and weather seal gasket
  9. 1 - 3/4" x 4' steel black pipe2 - U Bolts 3/4"wide x 1 1/2" long
  10. 2 - U Bolts 1 1/2" wide x 2 1/2" long
  11. 1 - 4" x 8" mild steel plate (Or what ever size you need )
  12. 50' coax cable RG8X coax cable
  13. solder
  14. electrical tape
  15. 1 -PL259 Coax plug connector Or what ever connector your radio needs.

Tools

  1. drill
  2. drill bits
  3. propane torch
  4. solder iron
  5. hack saw
  6. nut driver
  7. screwdrivers
  8. wrenches
  9. wire strippers
  10. emery cloth,wire brush or sand paper
  11. tape measure
  12. electrical tape
  13. coax jumper
  14. SWR Meter
  15. Radio

Step 3: The Radials

Do the following twice to build the 2 separate sides of the dipole.

  1. Cut 1 inch notches on both sides of the 1/2" copper pipe on one end of each pipe with the hack saw going down the length of the pipe. this creates a compression joint to later put the hose clamps on.
  2. Prep for Solder = Clean the opposite end of the 1/2" copper pipe with emery cloth and the inside joint of the 1/2" male adapters.
  3. Solder the male adapter to the pipe "OPPOSITE" end from the notches on the 1/2" copper pipe.
  4. Take a 3 to 5" piece of copper wire and strip on end and solder it "INSIDE" the end of the male adapter to create an electrical connection point that will later be connected to the balun. Do not get solder onto the threads of the male adapter. (Been there done that and it's a PAIN).
  5. Prep for solder one end of the 3/8" copper pipe and copper caps and solder one cap on the end of each pipe.
  6. Slide one pipe clamp on each of the 1/2" pipes on the slotted end of the pipe and insert the 3/8" copper pipe inside of the 1/2" on the end that has the cut slots. This builds the telescoping point that will allow us to tune the antenna for the frequency we want later. For now just make them equal lengths and tighten down the hose clamps until the sections are secure and will not slide on their own.

Step 4: Assemble the T

  1. Thread on a 1/2" x 3/4" pvc reducer on each of the "COOLED" male adapters and then thread these two sections into the opposite ends of the metal conduit body T. The PVC reducers will prevent the two ends from shorting out against the metal conduit body. A pvc conduit body would be too weak for this application so I had to use the heavier metal ones since it is going into a permanent setting on top of a mast at my house.
  2. Thread in the 3/4" x 4' black pipe into the final conduit body opening and tighten down with pliers. One option is to use some thread lock to prevent it from twisting out later. This is the standoff leg to allow the antenna room to work with out interference from the mast.

Step 5: Antenna Bracket Plate

Drill 8 holes the to insert the u bolts in the metal plate. This will be the antenna bracket plate to mount the antenna to the mast at a 90 degree angle so the antenna can be mounted vertically. However you can mount it horizontally if you desire. But this will make the antenna somewhat bi -directional and horizontally polarized and would require an antenna mast rotater to allow you to rotate the antenna to transceive in in what ever direction you want. Horizontally it would transceive somewhat equally in 2 directions with little reception or transmision pointed toward the ends of the antenna. So I kept mine vertical to allow it to work omni-directional (Vertically polarized).

Mount the standoff pipe to the plate with the u - bolts. Later mount this plate to the mast with the 2 remaining u bolts.

Step 6: Build the 1:1 Balun

Now build a 1:1 Balun. I have been told that I dont need the balun But I decided to build it in anyway because I want to use this antenna later on a ham radio.

http://www.zs6vd.bestwebs.co.za/1-1%20Hombrew%20Ai...

I built the balun using SM2YER design on his website. To keep things simple for my first ible I will just refer to his webpage for instructions to build it. I just made the feedpoint leads to come out the side of the balun instead of inline like he did his. See his website for building the balun. Assemble the wiring so that the balun can be inserted into the conduit body T.

Insulate any exposed electrical connection with tape, or liquid tape, etc... so that it dosent ground out against the conduit body.

Step 7: Final Connections

Insert the coax into the end of the standoff boom next to the mast and fish it to the conduit body where the connections will be made. Install your coax connector (PL259) on the opposite end of the coax.

Seal the end of the standoff boom where the coax comes in to prevent moisture intrusion with tape or caulk or what ever you have.

Make the wire connections and insulate any exposed wire with electrical tape or heat shrink tubing, etc...install the cover plate

Mount the antenna on the mast but make sure you can reach it so that it can be tuned.

Step 8: Tuning Your Antena

Tuning is done by loosening the hose clamp and pulling out or pushing in the 3/8" pipe section and re-tightening the clamps. But both sides of the antenna must be extended to the same length. Use your measuring tape to make sure both sides are the same. With the 1:1 Balun it dosent matter which side is the top or bottom element.

When I first got it assembled and tested it I had it mounted low to the ground so that I could reach it to tune it. My SWR reading was 1.2 on ch 1,1.1 on ch 20, and 1.2 on ch 40. But when I raised it up to full height the readings went up to 1.4 on ch 1, 1.3 on ch 20 and 1.4 on ch 40. I believe that its because is mounted too close close to my open stub J-pole antenna for 2m/70cm. But they are readings I can live with. i may get a longer standoff arm later but for now it works. However, I don't intend on using it for CB for long I am waiting to get a 10 meter HF soon and plan on re-tuning it for that band..

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    6 Discussions

    0
    alvenegas
    alvenegas

    13 days ago

    Awesome, thanks. I made one for 11 meters....with some modifications. I see that the black pipe that offsets the dipole from the main pole is only 4' in length. Do you have some interference with the other ground plane antenna? Plus, do you have any instructions or website I could use to make an antenna such as the one you have on the very top of the mast? Thanks!

    0
    JeremyM
    JeremyM

    Reply 13 days ago

    Thanks for the comments. I actually took this antenna down a few years ago. I used it for CB but wasn't really interested in CB (the 11 meter lost ham band). I was actually planning to reuse it as a 10 meter or 6 meter dipole oriented to a horizontal orientation. Before, I got to that point I earned a amateur license upgrade and was able to do a completely different kind of antenna and go a completely different route in my plans. But it was still a fun project that I learned a lot from. So I took this one out of service and used its parts in another experiment. I do that a lot.

    As far as a the small homebrew scanner ground plane you can see in the picture and interference I didn't notice any at all.

    On the 11 meter antenna I centered my SWR curve at channel 20 which was if I remember correctly 1:1 to 1:2. On channels 1 and 40 I had a max swr of 1:4 to 1:5 +/-.

    The small ground plane was another scratch build out of a need for a scanner antenna. its not really apparent from the photos but its also out on an arm from the mast. It just happens to be perfectly hidden behind the mast in the picture. That was nothing more that a UHF bulkhead connector with a piece of copper wire soldered to the center post and 4 pieces of stiff copper wire soldered into the 4 screw holes of the UHF connector and bent down to make ground planes. Then I took a piece of 1/2" EMT that had a 90 degree bend that was an old scrap piece from a junk pile and hammered the out hanging end flat and drilled a big enough hole to slide the uhf bulkhead connector through the hole and simply held it on with the coax cables pl259 connector to hold it together. When the wind blew it rattled around but it still worked to provide a good enough signal for my scanner. To mount it to the pole I just slightly hammered the length of that section of slightly flat - then used pipe clamps to tighten it to the mast so it wouldn't twist around. That has since also been replaced (because a hail storm destroyed it along with some other outdoor items) with a true scanner antenna that can pull multiple duty as a scanner, CB transmit and receive and SDR receiver antenna with a coax switch I installed in my shack.

    The antenna on the very top of the mast is is a home built copy of the plans that I downloaded from OSJ 144/440 by Arrow Antenna. Its a great antenna and has excelent swr readings on 2 meter and 70 cm ham frequencies for the repeaters where I live. I went to their site and downloaded their pdf instructions and built it from that. http://www.arrowantennas.com/inst/OSJ146440.pdf. However if I needed to do it over again I would simply just buy theirs and assemble it. Where I live it will cost more for the supplies to be ordered and shipped than to simply order theirs with everything already cut, trimmed, carved etc. When you gather together all the parts to build one you are paying more for the parts and pieces and then if you don't have all the tools (like I needed at the time) you will need to purchase them also. Right now their price is running around 59 dollars for the antenna. When I built that one and it was all completely done I think that the whole project cost me nearly 100 bucks. shop bought in this case is cheaper. But it was a fun project to build and again I learned a lot. the antenna was 59 bucks but the experience was an extra 41. :)

    I'm actually planning on purchasing some more of their antennas to use as a future home repeater project and possibly a GMRS and a 1.25 meter.

    good luck on the projects.

    0
    tomatoskins
    tomatoskins

    5 years ago on Introduction

    This is great! I love homemade soluitiions like this. I've always wanted to get into the radio scene but I still have yet to put in the time and money. Oh, and a very warm welcome to the site! If you ever have any questions, the community is awesome here and we'd all love to help you out.

    0
    revjmartin
    revjmartin

    Reply 5 years ago

    thanks. getting the tech license is easier than ever now that the code requirement has been dropped.

    And it has been a life saver for me. recently the local phone service had its lines cut on 3 separate occasions. ham radio was the only communications available for tover 5 counties. even cell towers were cut.

    0
    tomatoskins
    tomatoskins

    Reply 5 years ago on Introduction

    I've heard that it's a lot easier now. That's crazy aobut the phone lines!