Tag Archives: ham radio

Homebrew 6M “Plumber’s Special” Dipole

(Note: I wrote this a few years back, but it’s still a good design…so I thought I would share it here! – WWW)

The 6M band is becoming more active recently, but do you have the antenna to work it? No need to buy one, build it!

The 6M dipole is a VERY easy project for the beginner. You don’t even need to do any soldering! Copper pipe makes an excellent self-supporting dipole at this size, and using a CPVC tee as the center insulator makes assembly so simple!

Tools:
– Pipe cutter/deburring tool
– drill (this can be a hand drill or drill press, manual or electric)
– appropriate drill bits
– knife/cable stripping tool
– pliers

Parts:
– 1/2″ copper pipe (one 10′ length is more than enough)
– 1 CPVC ‘tee’ connector, 1/2″ (these are the beige plastic parts, they are sized to fit copper pipe)
– 1 pre-terminated RG-58 cable (any length, though you will be cutting it into two pieces)
– 1″ machine screws, 10-32, with washers and nuts
– zip ties

As part of my kit, I also have a quick mast kit – it should go without saying that this is a temporary field mast, not a permanent one!:

– 1 painter’s pole, 24′ extended
– 1 brush clamp for painter’s pole
– 3 coils utility cord (the 1/8″ diameter nylon stuff)
– 3 large stakes

All the above parts, with the exception of the RG-58, are available at Home Depot or Menards. I got the pipe, CPVC tee, hardware, utility cord and stakes at Home Depot, and the painter’s pole and brush clamp at Menards.

The basic dipole formula is what we use for the element lengths. (468/f(Mhz))/2 gives you the length of each half. Using 52MHz as the center point (you can calculate your own if you like), your full antenna length will be 9 feet, with each element being 4.5 feet. Simple! Cut two pieces of your copper pipe to 4.5 feet and deburr the ends. Press-fit the pipe into the opposing sides of the CPVC tee, making sure to seat them fully. At this point, drill a [1/8″] hole through the CPVC/pipe assembly on each side. Use a wood block on the back to reduce the amount of drill-through burring, and sand the surface flat again. These holes are for the machine screws, which will both hold the elements in place as well as give a connecting point for your cable.

At this point you need to attach your coax. I used the last foot of a piece of RG-58, sourced from Radio Shack. I don’t recommend much heavier cable than this, since we loop it over the top of the CPVC center and zip-tie it in place, so it needs to be flexible. You can use a longer length if you like, so you can include a basic matching loop at the feed-point (5 turns of coax, approx. 6″ dia., taped together). Strip 4″ to 6″ off the end, and separate the shield mesh to allow you to pull the dielectric through as close to the remaining insulation as possible. Remove about 1″ of the dielectric from the center conductor. There should be enough length between the split to reach each of the screws on the CPVC center without stressing the cable. Attach the center conductor to one side, the sheild to the other, and zip-tie the cable down to the CPVC. You’re done!

Well, almost. You should still test your tuning, though in my experience, these measurements should be pretty close. At most you may need to trim a little off the ends, but not too much. If you have access to an antenna analyzer, use it to check first. If you want to be able to fine-tune the antenna periodically, then you’ll need to do a little more work and a few more parts, specifically a couple 1/2″ end caps, a pair of longer machine screws, nuts, washers, and an appropriate tap to thread the holes. Drill a hole in the center of the 1/2″ caps, then tap it to the appropriate thread pitch for the screws you are using. Assemble the nuts to the longer screws, then thread the screws into the caps, using the nuts and washers to secure them so they won’t move. Solder them to the open ends of the pipe elements, being careful not to either fill the hole or solder the screw down so it won’t move anymore. Then you can adjust each element with the additional length of the screws in the ends of the elements. You can use brass screws for better conductivity over galvanized or stainless steel.

So, what about the mast? That’s VERY easy. [NOTE – DON’T put anything on top of the mast…you want to get it set up and secure before you load it up. Also, if you have a second person to help, this will go much easier, but you *can* do it solo if you need to.] Extend the painter’s pole completely. Take the ends of each of your three utility cords and tie a loop into them (individually), then wrap them around the third section of the painter’s pole, just above the second clamp. Place your three stakes in equal positions around the location you want to place your mast, about 12 feet from the center and drive them into the ground about half-way. Using Pythagoras theorem, a^2 + b^2 = c^2, you will need to tie off the free ends of your three utility cords to the stakes at about 20 feet…that is, measure about 20 feet of utility cord from the tied-off end on the pole, and tie it to each of your stakes. This should allow you to raise the mast by yourself, though you will probably still need to make some final adjustments for tension. If your cords are too loose, then lower your mast and re-tie all three cords equally shorter, then re-try raising the mast. If you have a second person helping, then one person can hold the mast vertical while the other adjusts/ties the cords. Once you have your guy lines adjusted, you don’t need to undo anything to lower the mast, just lift if off the ground and walk it down. You can then attach your antenna using the bottom half of the brush clamp and some additional cord or ball-bungie cords. Attach your feedline using a barrel connector, then walk the mast back to center secured postion, being careful not to tangle the antenna in the guys. If you want to rotate your dipole, just turn the whole mast!

Enjoy building this quick little 6M antenna, and enjoy getting on “the magic band”!

73 de N0XLT
Warren Werner

Field Day 2007

This Saturday/Sunday, June 23-24th is International Field Day 2007.

I will be in attendance at the Lincoln Amateur Radio Club Field Day station, starting from 8:00am to help set up.

This year, the LARC will be providing Amateur Radio License testing right at the Field Day site, so if you are ready to get you license, come on out and take the test!

We will also be running a GOTA (Get On The Air) station again this year, which gives lower-level and non-licensed people a chance to get on the air and see what all excitement is about! There will be appropriately licensed control operators available to help you out with any questions or difficulties you may encounter.

Since this is a 24-hour affair, I will be camping out on-site. We will be set up in the Lincoln/Lancaster County VA Hospital parking lot, located at 600 South 70th Street, right across the street from St. Elizabeth’s Hospital.

Come on out and have some fun with us!

Warren – N0XLT