for less than a double sawbuck!
by N6XN
Gary and I were kicking around some ideas about building a portable HF antenna for camping trips. We decided that it had to be:
Cheap
Lightweight
Small enough to fit into the trunk of a car
easy to put up and take down
cheap
PVC pipe was the obvious candidate for the material since it is cheap, lightweight and really easy to work with using ordinary handtools.
The mounting details were a little sketchy until Gary came up with the idea of using a plastic "Homer Bucket" full of sand. I thought that maybe concrete would be better because then you wouldn't always be digging cigarette butts and cat doots out of your bucket (kidding kidding!) The real reason was I had a couple of sacks of concrete left over from a fence project.
Here are some of the details of the project. I don't have detailed measurements because fine tuning with a SWR bridge is half the fun of building an antenna. Click on the photo to see a large version.
Here's the base; a "Homer Bucket" full of concrete with a short piece of PVC pipe embedded in it. It violates at least one of the requirements: It ain't light. But it is not likely to let the antenna fall over either!
Here is the base section and by far the most complicated part. We start with a 1" tee. After assembly, the antenna is stood up and slipped into the stub in the bucket. If you study the photo you will see that we installed a SO-259 4-hole connector in a slip on cap. The connector is fastened to the cap using 6-32 screws fitted from the inside out and double-nutted. The next photo shows a little more detail.
Like any 1/4 wave vertical, it just won't work without radials. We started with 2, just a couple of short stubs and terminated on one end with an automotive type ring terminal and on the other end with an Anderson Power Pole connector. The ring terminal goes between the 6/32 nuts on the coax fitting. By using the Power Pole connectors, we can carry several, cut for different bands. The radiator, a length of 22 Ga. stranded and insulated wire is soldered to the coax fitting center and threaded through a small hole drilled in the tee as shown. During assembly, pull the wire through the hole as you slip the cap on the tee to eliminate any unnecessary slack.
In this photo, the radiator is wound in a spiral around the PVC section and taped off at the end of the section. The wire is cut and fitted with an Anderson Power Pole connector. It doesn't matter which direction you wind the wire, in fact you don't need to wind it at all if you don't want to but it does help shorten the overall height of the antenna if you do. The second section is slipped into the first section about 6 inches, a connector is fitted onto the left over wire and then it is taped in place so the wire can be wound around the second section. We used 3 dimensions of pipe: 1" for the base and bottom section, 3/4" for the middle section, and 1/2" for the top section. If you have played around with PVC in the past, you know that these dimensions will not slip into one another, no siree! But after Gary massaged the bottom 6 inches on the two top sections with a strip of sandpaper, the pieces fit together perfectly. A little Armor-All or furniture polish will keep the pieces from sticking so they can be easily disassembled.
Here Gary shows off his new antenna, ready to go camping. We don't show construction details of the top section because it is exactly the same as the middle section. We did add a PVC cap to to very top just to finish it off.
Some general notes: While this antenna will withstand the rigors of all kinds of weather, the connectors are not made for outside environments and they will eventually corrode. It couldn't hurt to work a little No-ox into them. While the sun won't hurt the PVC, it's pretty hard on the wire insulation so don't plan on leaving this antenna up for years at a time.
Now for the dimensions: This antenna was cut for 20 meters so we used a total of 16 feet of pipe above the tee. By using the formula of 234/f (mHz) you can calculate the length of the radiator and the radials. A 40 meter version of this same antenna would be twice the height and the radials would be twice as long but it is doable, just not as portable. You could also scale this antenna for the higher bands as well.
If you don't use Anderson Power Pole connectors, just about any good quality connector would work, just do what you can to keep it dry. Water and RF don't really get along very well.
Does it work? First contact first call: a KL7.
