their line filters are rarely effective, they do occasionally help, and they might find some unique problem in your local wiring or instruments. (But don't count on it: Since the divestiture of AT&T several years ago, I've found the local operating companies critically lacking in technical talent.)

If worse comes to really worst (like civil actions, threats with deadly weapons. etc,—don't underestimate the actions of a neighbor who can't use his telephone!), experiment with band and power changes. If you clobher your neighbor's phone when using 100W on 20 meters, try 10. 12, 15, 17, 30. 40. 80 meters instead. Or you might try reducing power to the minimum required to make contacts (which is a procedure we re all supposed to follow according to FCC Pan 97. anyway). Although rm an advocate of "Why use low power w hen a kilowatt will do the job?" thinking myself, experimenting with operating frequency and power level might reveal some useful data. You might find that the interference is frequency-specific, for which the obvious conclusion might be that the telephone wiring in question is resonant on some hand you choose to operate. Tl is is good to know, because telephone wiring can be altered in length without any notable change in performance. and simply adding or subtracting some length to your neighbor's telephone instrument wiring might shift the resonance out of the band you're try ing to use.


Filters on your transmitters will be of absolute!} zero help with telephone interference; however, a good low-pass lilter on your HF transmitter might help reduce TVI ("might" is the key word here—don't count on it). If you're using modern-day equipment, with a high-quality coaxial transmission line connected to resonant antennas that are well matched, a low-pass filler may not help at all, but that doesn't mean you shouldn't try one. If you do try a low-pass lilter on your HF transmitter, get one that is well-shielded and raied for considerably greater power output than you ever intend to use. Transmitting filters used on VHF-UHF transmitters almost never help reduce interference to appliances not intended to receive amateur radio signals.

If you're using an ''end-fed wire" HF antenna, this is often asking for trouble. Although end-fed wires work just tine on any frequency where the wire length is not a half-wavelength, it usually means strong RF fields inside your own home, which can coincide with angry family members. There are some compelling reasons to use end-fed wire antennas (like no transmission line loss, regardless of VSWR), but if you have TV I/RFI/telephone interference, they are best avoided.

Experiment with grounding. Sometimes a good, low-impedance ground on your transmitter, or the interfered-u ith appliance, or both, can help. However. I've seen as many cases where a good ground makes no difference at all. and some cases where the grounding actually made interference worse. ""Grounding" is not a magic cure. I f you decide to try grounding, there are a few points to ponder:

1. The primary reason for a station ground is not to reduce interference. l! is a safety precaution that can help save your life should other grounding systems (such as through your three-wire AC line cord) fail. Grounding station equipment can also help prevent fighi-ning damage in the event of a direct or secondary strike, but is by no means a "fail-safe" precaution. At least one ham I know lost his home to a direct lightning

73 Amateur Radio Today ' January 1996 47

strike. e\en though his station was as well grounded as any I've seen.

2. There are differences between types of "grounds," A DC ground is any ground path that eventually le:*ds to earth, no matter how long or resisii\e it may be, An RF ground i^ one offering low impedance (not necessarily resistance) to earth on a specific frequency or range of frequencies. It is almost impossible to achieve an RF ground at VHF-UHF since the path to earth would ha\e to be jusi a few inches long at most. At HF, a true RF ground is achievable, but not easily. One example of a reasonably effective RF ground is the one that I use: a pair of K'-long copper-clad steel ground rods driven into the earth directly below my operating bench (which is in the garage), connected to the station equipment using 2"-wide tinned copper braid capable of conducting more than 1.000 amperes of current. Such braid costs about S3 per foot retail and isn't easily found. Also, not many folks can install ground rods directly below; and less than five feet from their station equipment. I did it by using costly masonry drill bits (I "-diameter) to drill through about one foot of solid concrete in my garage floor then using a 16-pound sledge hammer to pound the ground rods in- This task took several hours to accomplish, since drilling through 12" of concrete isn't easy, and the ground was fairly hard. It also used up two masonry bits costing more than $30 each. And the work would have been impossible to do if the station had already been installed, {I did it prior to building the operating bench or installing any equipment,) Was h worth the expense and effort? Probably not. Do I really have an effective RF ground? Maybe. I w outdn't bet the farm on it.

tf you have a second-story (or higher) ham shack, the likelihood of getting a real RF ground to your station is minimal, You're loo far away front earth. How c\ er. this does, not mean you cannot achieve a tuned, or frequency-specific, RF ground for a particular frequency of operation. One reasonably effective "counterpoise" (artificial ground, which works for RF but is neither a DC ground nor a hazard-pre venting ground) is to use a quarter-wavelength "radial" of wire connected to the ground post of your equipment, with ihe free end connected to nothing at all! Trust me. it works. The MFJ product which effects an artificial ground and is tunable might also work in some cases.

Cable TV converter boxes also var\ in mr workmanship and engineering quite a hit. Some are in plastic cases which arc complete I) unshielded. Some are in metal enclosures which appear to be an effective shield, but really aren't. Most have only two-wire AC line cords w hich provide no grounding at all. In some cases I've seen, simply shielding the converter box using household aluminum foil has helped reduce TV I. These "boxes" are really cheaply made and designed to a price, rather than performance. specification. They should cost hundreds of dollars to perform their intended tasks, but in reality they sell for very little and barely work. Most have the insignia of tin American company on them, but they're actually built offshore, in Taiwan or somewhere with even lower labor costs. There's nothing wrong with offshore manufacturing, except that these factories often cut corners on what were already cheap designs. If it has an AC power cord on it, the equipment is undoubtedly "UL Listed," which

"Many consumer devices such as personal computers and modems are "FCC Class B" accepted, which similarly means nothing at all"

means absolutely nothing with regard to performance.

Check your antenna system, too. If if s an old installation, your connections could be oxidized or corroded, which can help generate higher levels of interference than a system built with shiny new components. Also check your coaxial cable. Brand-new. high-quality coax made by reputable manufacturers is usually pretty good; but lower-cost cables, surplus cables, or ones thai have been in use for a few years or more may not be. Coaxial cables, especially when used outdoors, do deteriorate and require replacement.

While SWR is not a figure ol merit for antenna performance, it can be an indicator of something being right or wrong. If you are using an antenna with a high SWTR and "tuning" it in the shack to make it match better. there is still a mismatch between your fecdline and your antenna, and there arc still standing waves on your transmission line. Antenna mismatch will often cause transmission line radiation, which may tend to make interference problems worse. Adjust your antennas so they match your transmission line. This is not only more effective than using antenna tuners, transmatches, etc., it can also help reduce radiated interference.

You might also consider raising the elevation of your antenna, to get it farther away from the appliances you're interfering with, I had an interesting experience with TV I on b meters (50 MHz). This band is notorious tor causing problems with TV Channel 2 reception, since 50 MHz is very close in frequency to TV Channel 2 to begin with. ! was running 100W output power to a six-element beam up about 35 feet, and causing TV! to two or three neighbors. 1 tried several cures, none of which worked. In desperation. I finally tried raising my b meter antenna. 1 raised it to 45 feet then to 55 feet, and finally to 60 feet, while testing for TVI. All these changes took some time, as I was adding tower sections!

Two weeks or so later, after adding the last tower section that raised the beam to 60 (eet. I ran some TVI tests with the neighbors again. The interference had literally vanished! I raised my transmitter power. Eventually, i! had I200W output power on 6 meters (from a pair of 3-50GZ s) and iiterally zero TVI. Pre\i-ously. I had se\ere TVI with ihe same transmitting equipment (and much low er power) and the same beam antenna, but the beam was up only 35 feet. The difference was that when the beam was up 35 feet, it was only slightly above my neighbors' rooftops, and nearly in line with their TV antennas. By raising the antenna another 25 feci I was vvcll above their homes and their antennas, Hi us considerably reducing the strength of my radiated signal lo their TV antennas, even when operating at far greater output power.

Agency Approvals

They mean absolutely nothing. Really, Many consumer electronic and electrical appliances are TIL 1 is ted." *UL recognized." "FCC Class B approved," and so forth. It doesn't mean a thing. U,L,

(Underwriters Laboratories) and C.S,A. (Canadian Standards Association), as well as many foreign agency approvals (T,U.V+1 V.D.E,, etc., ad nauseam) don't meal anything in the real world. Many consumer devices such as personal computers and modems arc "FCC Class B" accepted, which similarly means nothing at ail. While PCs and peripherals are all 'Class B approved," they radiate RF energy like mad, and can similarly receive RF energy that can render them useless in strong RF fields.

U.L. and other agency approvals have nothing to do with performance. U.L, employs almost no reaj engineers, and has literally zero experience in RF interference or other real-wror!d situations. They "list" or "recognize" equipment based on safety criteria {meaning, the equipmeni probably won't catch fire

Glutton For


Wayne's published a 32-page booklet of his yet-to-be published 73 editorials, in case you just can't wait, or are looking for some cheap, fun reading. 32 pages of small print, so it's packed with ideas, mind-expanding material and book reviews that you'll eventually see in 73.

$5 postpaid from Uncle Wayne's Bookshelf,

70H N202, Peterborough NH 03458. Or call 800-274-7373 and ask for "73's Yet-To-Be Editorials."

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