Antennas:

The Part That Gets You Heard!

WHY ANTENNAS?

One of the traits of amateur radio operators is to be an experimenter. In the early days of amateur radio, hams built their own radios. These days, commercially built radios are so good and relatively inexpensive that it's less usual for hams to build their own. It's much more likely, though, that hams would build their own antennas. I started with a simple antenna for digital television, advanced to build some amateur radio antennas, and even built an external antenna for my home weather station. Below, you'll find some of the details of those builds.

WIRELESS WEATHER STATION ANTENNA

EXTERNAL ANTENNA FOR OREGON SCIENTIFIC WMR-968 WEATHER STATION - This popular weather station, that was also sold under the Radio Shack brand, incorporates wireless sensors to detect various weather conditions. The sensors, though, have a limited range, that in my case, led to inconsistent readings. The manufacturers claim "up to 100-feet" reception, but that is under perfect conditions, in warm weather with no intervening walls, etc. It's like rating a cars top speed going down a steep hill with a tailwind! Because I've been building antennas for my amateur radios and because the weather sensors transmit and receive on a frequency just below one of the most popular "ham" bands, I thought I'd give an external antenna a try. Although these instructions are for the WMR-968, it's likely that other Oregon Scientific and other brand wireless weather stations are similar. All this is done at your own risk. I take no responsibility if it doesn't work, or if you damage your console. If you choose to build a J-Pole antenna, you'll be soldering copper pipe, so be careful with the open flame! As for the project, I can only tell you it was pretty simple to do and worked for me. After about six months, I haven't had a sensor drop connection! Here's what I did;

Choose The Antenna - This can be a simple as just removing the built-in antenna from the console and moving it to a better location. You also can find a variety of commercially made antenna ranging from directional (has to be pointed at the sensor) to omnidirectional (receives in all directions) with varying prices to match. Because I've been building "J-Pole" antennas for amateur radio with good success, I decided to build a J-Pole antenna, cut for the 433mhz band at which the weather station operates. J-Poles are typically built from 1/2" copper plumbing pipe. Now copper prices have gone crazy recently, but I was fortunate enough to have scraps available. I found an Application that calculates the dimensions of the J-Pole and includes assembly instructions. I found two challenges building this antenna. The first was that some of the dimensions are pretty small. The distance between the two vertical pieces calculates to 6/10ths on an inch. I found that if I used a standard "Tee" fitting and a standard "elbow" fitting the two pieces were an inch or more apart. I solved this problem by using a standard "Tee" and a "Street Elbow." A standard "elbow" has two female ends that slip over the copper pipe. A "Street Elbow" has one female end and one male end, the latter I inserted into the "Tee" fitting resulting in a spacing of about 3/4," which is close enough for a receiving antenna. I'll talk about the second challenge and a possible work-around in a bit.

Build the antenna - Once you've gathered your materials (about 3-feet of 1/2" copper pipe, a 1/2" copper "Tee," and 1/2" "Street Elbow," and two 1/2" pipe caps (optional, but recommended)), it's time to assemble your "J-Pole." The first step is to cut the 1/2' copper pipe into three pieces. You'll need a piece 19.56" long, a piece 6.48" long, and one short stub (length not critical, this piece only provides a mounting surface). Next, clean all the pipe ends and fitting surfaces with a plumbers cleaning brush or sandpaper. Clean joints are critical for a good solder joint! Note: If you're concerned about appearance, you may want to clean the entire piece. Once assembled, a coat of polyurethane will keep it looking good. After you've cleaned the parts, it's time to assemble the pieces. The male end of the "Street Elbow" goes into the "short" side of the "tee," the long piece of copper pipe goes into the "top" of the "tee" and the short piece (the 6.48" one) goes into the female part of the "Street Elbow." The remaining piece goes into the "bottom" of the "tee." Make sure the pieces are fully seated into the fittings and that pieces are parallel or at right angles as is appropriate. There is enough movement in these fittings for pieces to get significantly out of alignment. Now, it's time to solder, or "sweat" the joints. Be Careful! Plumbers torches and molten solder can cause painful and serious burns. Pick a location where it's safe to use an open flame and has good ventilation! A good plumbers torch (Bernz-a-matic or similar) will work. I prefer Mapp gas to propane because it gets hotter and I can get the joint hot enough to flow the solder before adjacent joints have time to get too hot. Don't use plumbing solder! Plumbing solder has an acid based flux that may eventually effect the electrical connection between the pieces. Instead, use electrical solder. To insure good joints, heat the fitting, not the pipe. The heated fitting will draw the solder into the joint, ensuring a good connection. Use only enough solder to seal the joint. Using too much will result in an unattractive joint and won't be any stronger. A good rule of thumb is to use 1/2" of solder for a 1/2" copper joint. I like to have a moist rag handy to clean a cool the joint after the solder is applied.OK, you've built your antenna. Now it's time to make your connections.

Connect the cable to the antenna - A good choice of cable is RG-58. This is an inexpensive coaxial cable that is easy to work with. RG-58 does have significant loss at 433mhz but this antenna should provide such a great improvement that you'll still experience a big net gain. If you don't have a good local source, All Electronics has a good selection at reasonable prices. I bought a cable that had BNC connectors on each end. The BNC is a good, reliable connector and allows me to disconnect the antenna from the console if I need to change batteries or make other changes. A cable without connectors can be used, as well. I cut one end of the cable about 12-inches from the end. We'll get to the cut end in a bit. Feed the cut end of the long part of the cable to the location you plan to install the antenna (outdoors, in my case). The end of the long cable with the BNC connector still attached goes to the console location. Carefully strip about 1-1/2" of the outer jacket from the cut end of the long cable. Peel back the braid and twist it into a bundle. Cut and remove the foil insulator. Strip about 1/2" of insulation from the center conductor. Now it's time to connect the cable to the antenna. This is where I encountered the second challenge. It's difficult or impossible to get the copper pipe hot enough with a soldering iron to make a good soldered connection. Using a torch, however, gets the pipe hot enough, but its difficult to do it without overheating the cable. If I do it again, I think I'll use two stainless steel screws to make the connections. Drill two holes, one each in the 19.56" piece and the 6.48" piece. These should be 6/10ths of an inch above the horizontal surface made when you connect the "Street Elbow" to the "Tee." Attach the center conductor to the taller piece and the braid to the shorter piece. The last step is to make these connections water resistant. There are several products made specifically for this purpose, but, I find, a good quality electrical tape or rescue tape seem to work well. Next, mount the antenna.

Mount the Antenna - Antenna mounting is pretty much a individual effort that should be customized to your situation. In my case, just took a short piece of scrap 2x4 and drilled a hole in one end big enough to accept the mounting stub of the antenna. After priming and painting the 2x4, I then attached it to my house using Pocket Screws. As the saying goes, "your mileage may vary!" The next, and last, step is to connect the cable to your console.

Connect the cable to the WMR-968 console - Open the console by removing the three screws from the consoles bottom. You'll find one of the screws under the battery door. If you're careful, this can all be done without removing the batteries, but, if you're using the DC cord it's easier to remove the batteries. I generally don't recommend working on a device while it's connected to external power, but this can be safely done if you're careful, and, keeping the console powered-up avoids losing your data. Next, separate the two halves. Once opened, you'll find the factory antenna connection. The antenna is physically attached and electronically connected by a single screw. Remove that screw and set it aside. Remove the factory antenna. Prepare the cut end of the short cable with the BNC connector on the other end. As you did on the antenna end, strip about 1-1/2-inch of the outer insulation. Peel back the braid and twist it together. Remove the foil from the center conductor. Strip the insulation from the center conductor.Leave about 1/4" of insulation showing. Cut the center conductor leaving about 1/8" of conductor showing. Attach a spade connector, or similar, to the center conductor. This can be done by crimping, soldering, or both. You could also just twist the center conductor around the antenna connection screw.You'll likely find you need to use one, or more, small washers make-up for the smaller thickness of the spade connector or center conductor. The last connection is the braid, which is typically connected to a good chassis ground. I was unable to find a schematic, and others on the net report being unable to get one, as well. I decided to try a temporary connection until I could learn more. I just stretched the braid over, and in contact with the metal cover that is adjacent to the antenna connection. I used an existing chassis screw that kept the braid in contact with the metal cover. Although meant as a temporary solution, it is working so I may leave it alone. Carefully reassemble to console, rescan for your sensors, if necessary, and you should be off to the races. And that's it. Hopefully, all your sensors will provide accurate and consistent data. Let me know how this works for you!

AMATEUR RADIO ANTENNA

Since I'm involved in emergency preparedness, I wanted an antenna that gave me excellent signal, but was still portable. I had heard about a design called a "J-Pole" (named for it's shape) that not only performed well and was relatively small, but it could be made from common plumbing pipe. Since I had a bunch of copper pipe scraps and fittings, this sounded right up my alley. Once again, I went to the web and found several plans for "J-Poles" including a "Super J-Pole" that works both on the 2-meter and 70-centimeter radio bands. But the plans I found lacked one important thing, true portability, mainly because the antenna is quite long. So it was off to dreaded Home Depot to browse their plumbing and electrical aisles. Since the existing design was made of 1/2" copper pipe, I quickly decided to use male and female threaded fittings to allow me to divide the long section into three pieces. I also found some electrical "lugs" that perfectly accepted the 1/4" copper tube that connects the 1/4-wave and 1/2-wave sections that make the antenna "super." These modifications allow me to quickly assemble and disassemble the antenna and to carry the pieces and the photographic tripod that I use to support the antenna in a slim canvas bag I found. I keep the antenna in the back of my truck, and I'm ready to go. The photo at the left is of a second super j-pole I built for permanent mounting on my house. It's the same, except it lacks the quick disassembly capability.

DIGITAL TELEVISION ANTENNA

The first antenna I built was for UHF television. Since the analog to digital conversion, most television stations have been moved to the UHF band. This was done so the FCC could sell off some of the frequencies formerly used for VHF television. Some of the digital stations stayed on the VHF band. Anyway, I get my television both from Direct TV (satellite) and from an outdoor antenna. But one day I heard about building a home brew digital television antenna from, believe it or not, coat hangers. I found several instructional videos on building such a Digital TV Antenna antenna on You Tube. Not being one to build it exactly the same as was done before, I decided to use 12-gauge copper wire instead of coat hangers. My thinking was that copper wire would be a better conductor than coat hangers, therefore, it might work better. I built my antenna (pictures coming soon) and took it to my friend Howard's house. Howard and his wife had just purchased a new High Definition television, but didn't have a digital TV source. So they were a perfect test site, except for one thing, they're about 35-miles from Mount Wilson where most of L.A.s T.V. transmitters are located. I connected my antenna to their new television and set the tuner to scan for new channels. Surprisingly, it found about 30-channels! We were receiving all of the major channels except for two that are still on VHF. Picture quality was really good with few drop-outs.