From: "James R. Duffey" Date: Sat, 19 Mar 2005 10:04:36 -0700 Over the years I have found the inverted-vee resonant dipole to be my all round best antenna for quick portable operations. For single band operation, a single band dipole fed with RG-58 is manageable, easy to erect, and requires no tuner. For multiband operations, I use paralleled dipoles erected as an inverted vee. One could also use a trap dipole, but they are a bit more hassle to set up. On parallel dipoles, the low band dipole tends to effect the high band more than vice versa. So start out with the low band dipole and get it to work right with an SWR minimum where you want it. Then add the high band dipole and adjust its SWR minimum where you want it. The low band should be OK, or at least not changed much. Don't change the low band dipole to get the high band dipole to where you want it. That is a lowing battle. This, by the way is the opposite of trap dipoles, where you want to start at the high frequency and work down. It also helps to separate the ends of the parallel dipoles as much as you can to reduce interaction. If tall trees are available, they are probably the best center supports. For quick contests, you only need to get a wire over one of them to get the inverted vee in the air. For more serious operations, like Field Day, you may wish to erect them as a dipole as there is a small height advantage and sharper pattern advantage. I use painter's poles for center support if tall trees aren't present. These are telescoping aluminum with a fiberglass base section. The 17 foot models cost $24 and the 24 foot one cost me $35. You can buy these at Lowes or Home Depot. The 17 footers are usually available. The 24 footers are not as common, but if you keep your eye open every time you go in the store, you can usually find one. Bungee cord the pole to a fence, guard rail, sign, picnic shelter or whatever is handy. The painter's poles support a great deal more weight than the crappie poles and the 33 ft German and MFJ poles. They are more rugged and less likely to break. I run them with about 6 inches still telescoped in to the previous section, which makes them stiffer. These are obviously not suitable for backpacking operations, but for portable operations from a car they are fine. They can be easily erected by a single person. In my experience, guys are not needed. I make dipoles with center insulators from PVC Tees. These slip right over the end of the paint pole. I feed them with RG-58 or RG 8X. I use a coax balun made following W7EL's instructions. Wrap the feed line slowly around the pole as it descends to avoid it flapping in the wind. One could connect the aluminum sections of the pole together with a jumper and feed them as a vertical, but I have not tried that. With dipoles/inverted vees, if you cut and tune it before you leave in the same configuration, you shouldn't need a tuner. A 40/20 parallel inverted vee will take care of the two most used QRP contesting bands and 15 M can be worked with the 40 M dipole in a pinch. If you have a multstation setup, a single band antenna for each station is easier to deal with than multiple band antennas. On the other hand, multiband antennas can be used on more than one band if something goes wrong. I tie 75 feet or so of mason's twine or monofilament to the end of the dipole without using an end insulator and wind it all up on a narrow shuttle. The shuttle has a couple of notches the width of the cord on one side of the shuttle like a tent guy tightener to fasten the end without tieing knots. The shuttle with the twine is narrow enough to fit through the openings in a chain link fence material. After I erect the antenna, I unwind enough cord to give the antenna a shallow vee shape, feed it around a support, like the chain link fence, a post, rock or even tent stake, put the cord on the antenna side of the support through the notches in the shuttle and adjust the tension. The notches provide enough friction to keep the twine from slipping. This is quick and easy to set up and take down an inverted vee. I am still working on the shuttle material, the twine and wire put a lot of tension on the support and my initial attempts from paint stirrers and yard sticks failed. The grain ran the wrong way. PVC cut from a pipe should be much better. I need to make up some new ones. Of course all this is very dependent on location. N4BP has a good signal from the Florida keys with an old 14AVQ bungee corded to a guard rail a few feet from the Gulf of Mexico. That won't work here in the desert. Elevated locations with sloping ground in a direction with a large ham population is ideal. Even low antennas work well there. For a daytime only operation on 40 M you can get by with a low antenna as most of the stations will be close in. At night it is another story. Since 20 M is the bread and butter band for most QRP contests, it probably pays to erect the best 20 M antenna you can. Nonresonant antennas fed with ladder line, such as the 44 ft and 88 ft antennas, or a 40 M dipole used on 20 M, are a poor choice for use as inverted vee antennas on bands where they are longer than a half wave. This is due to the antenna having the maximum current point closer to ground on the higher bands than the support height which leads to undesired high angle radiation and reduced gain in desired directions. These antennas are better erected as dipoles, with both ends supported. Verticals have the problem of requiring radials, which tend to get in the way underfoot when operating portable. An elevated ground plane will work fine, but is usually more work than the inverted vee. If you must use a shortened antenna, remember that very low dipoles can be very lossy, and on 20 M and below, a Buddi-pole or other shortened dipole erected at less than 10 ft will probably be out performed by a loaded vertical, such as the PAC-12 with even an average radial field. When operating portable tt pays to bring backups for everything, even the antennas. So, you might want to throw that old ham stick in the car, even if you are planning on erecting an inverted vee. You never know what might happen. And that old SW-20 + will at least allow you to make some contacts if that K1 takes a dump. Replace the batteries in everything that needs batteries and bring spares for all the devices that require batteries. You might not need them as you have already changed them, but your buddy might. Adapters are always required and it is easy not to have the right one. I have started to make plugs with alligator clip pigtails attached to them for every jack on each piece of equipment I use. That way, I can make my own adapters in a pinch. This is longer than I intended. I hope that it helps someone. - Dr. Megacycle KK6MC/5 -- James R. Duffey KK6MC/5 Cedar Crest NM 87008 DM65