During this year's antenna-fixin' season, many skyhooks will be given a good cleaning. While steel wool and elbow grease are the traditional "solvents", it has been pointed out by many that Scotch-Brite(tm) pads do the job better than steel wool and leave no tiny steel slivers in the antenna or your skin to rust or itch, respectively. When you put it all back together, don't forget to use the anti-oxidation compound!
Another antenna tip -- if you have two nested sections of tubing that are not coming apart easily, squirt a little penetrating oil (such as Liquid Wrench or Kroil) into any slots or screw holes. Then try to get the inner section turning in one direction. Keep turning it in the same direction as you pull it out. The burrs or obstructions that are binding will wear down or flatten if the direction of turning is consistent. If you need to grip the section with pliers or other mechanical device, insert a wooden dowel first to keep the tube from being deformed. Brett VR2BG contributes a simple assemble-and-test method for constructing gamma matches:
- Strip sheath & shield off length of RG-8 (start longer than predicted at approximately 20 pF/ft)
- Shove into gamma tube - tube ID should be very close to OD of insulation.
- Gradually trim the length.
- Waterproof both ends of the tubing.
For calculating the expected length, try the calculator program at www.ve3sqb.com (Scroll down to the "for the xperimenter" section or do an in-page search for the word "gamma.") The calculator provides spacing, gamma tube length, tap point on the driven element, and insertion length. The app suggests that the gamma tube (outer tube) be 1/4 the driven element size. Tom W8JI has also published info about the gamma match and how length and diameter affect the network. www.w8ji.com/omega_and_gama_matching.htm . (Thanks, Aaron NN6O)
Everybody uses them, but not many know about the genesis of the ubiquitous SWR meters found in shacks worldwide. For the original article, download and enjoy Warren Bruene's original article, "An Inside Picture of Directional Wattmeters" from April 1959 QST. It is on the ARRL Web site at www.arrl.org/tis/info/pdf. (Thanks, Larry N8LP)
Rex K7QQ suggests using anvil-style pruning shears for cutting coax from RG-58 through thicker sizes. He says that it gives a nice clean cut through the braid and center conductor. I'm sure it beats gnawing through the cable with regular diagonal cutters.
Another tool-worthy contribution was made by Julius N2WN in response to the tips on getting aluminum tubing apart. He suggests using oil filter-style wrenches that are available in small sizes and do not damage the tubing as locking pliers would. Sears apparently carries a two-size set that will grab tubing as small as 1/2" in diameter!
Class D amplifiers, first proposed in 1958, have become increasingly popular in recent years. What are class D amplifiers? How do they compare with other kinds of amplifiers? Why is class D of interest for audio? What is needed to make a good class D audio amplifier? What are the features of ADI's class D amplifier products? Find the answers to all these questions and more by reading the Analog Dialogue article at http://tinyurl.com/gafae.
D-STAR technology is often mis-identified as "just digital voice" but the standard has a lot more to offer, particularly for high-speed data transmission. The Texas Interconnect Team www.k5tit.org is working on some advanced D-STAR applications that may surprise you!
Technical URL of the month -- It's lightning season! Roger N1RJ points us to a good site for info about lightning protection: www.polyphaser.com/ppc_ptd_home.aspx. "As you will discover, the subject of lightning protection is not as simple as it first seems. There is a lot of bad info on the Web mainly from well-meaning folks who only know about power line grounding at 60 Hz. A good power line ground is usually not a good lightning protection ground but a good RF ground (radials) is usually good for both. Also, proper bonding is as important as the ground system."
73, Elmer W6IGK