by Daniel A. Grunberg -- Kensington, Maryland U.S.A Modern shortwave receivers, particularly modern portables, tend to be very sensitive. Modern shortwave receivers most often are intolerant of overly strong signals, even strong signals well away from the frequency being tuned. For example, a local, strong MW station might overload your receiver's front-end. The result could be images all over the SW bands, or it could be an apparent lowering of the receiver's gain. Therefore, IMHO the best (and least costly) antenna is the least antenna that can receive what you want to receive. I'd try the following in turn, and stop when I was satisfied with the reception I was getting. 1. The receiver's built-in antenna. 2. Up to twenty feet of wire (insulated or not) strung up as high as is convenient, inside the house. Radio Shack has a reel-up wire for this purpose (278-1374), which easily can be taken down and stored when not in use. Ask about Radio Shack's return policy, in case it doesn't work for you. 3. Grounding the receiver and using antenna 1 or antenna 2 (above). The following grounding methods may increase the received signal-to-noise level, BUT THEY WILL NOT NECESSARILY PROTECT YOU, YOUR HOUSE, YOUR PROPERTY, OR YOUR RECEIVER FROM LIGHTNING. REMEMBER, EVEN DISCHARGES OF STATIC ELECTRICITY AT LEVELS COMMONLY FOUND IN THE HOME HAVE BEEN KNOWN TO DAMAGE SOME RECEIVERS. Almost any sort of external ground _may_ help. Improvised, less-than-ideal, external ground connections have been known markedly to increase signal-to-noise ratios. Sometimes just touching your receiver may make signals more readable. That's because your touch is increasing the capacitive coupling between the receiver's circuit ground and the earth. If there is no easy way to make a connection to the receiver's ground, a grounded sheet of metal that's has roughly same dimensions (or larger) as one of the larger sides of your receiver (a cookie sheet will serve for this) can be used instead of your hand. Just use a clip lead to connect the sheet of metal to a cold water line or one of the other external grounds that I describe below. Then lay or stand the receiver (whichever works better for you) on the sheet of metal. It's a marginal connection to ground, but it MAY work for you. If your receiver has an external antenna connector, an external ground connection usually may be made via the sleeve of the connector's mating plug (see illustration below). Inserting the plug into the receiver's antenna connector will disconnect the receiver's antenna from the receiver's front-end. A clip lead, from the appropriate lug on the plug to the base of the whip antenna, can be used to reestablish a connection to the receiver's _whip_ antenna. ||__________ ||__________||0 <--- to rcvr front-end || ^ to rcvr gnd You can try to eliminate the clip lead from the plug to the whip antenna by cutting the antenna plug. What remains of the long part near the wire terminals (which were not drawn on the left part of the figure below) should be long enough to makes a non-intermittent ground connection when it is inserted into the radio's antenna jack, but should NOT be long enough to operate the antenna jack's switch and disconnect the antenna. The following figure shows what I mean. The figure is not to scale, so no dimensions should be inferred from it. [Actually, since I haven't tried cutting a plug, I don't know what the dimensions should be.] ||______ ____ ||______ ____||0 || ^ ^ insert throw this part this part in receiver's away antenna jack The best way to ground your receiver is to connect its ground to a ground rod (Radio Shack has them, but I don't know the catalog number) driven into damp soil, as near to the receiver as possible. The next best external ground connection is to a ground clamp mounted on a metal *cold* water line. Ground clamps and ground rods often can be found in the electrical supply section of your local hardware store. Usable cold water line connections also may be made by clipping a battery clip (Radio Shack 270-344, perhaps) to a cold water line, or by clipping one end of an ordinary clip lead to the handle of an UNPAINTED cold water cut-off-valve handle. If you clip onto a plumbing ground, be sure to polish its surface lightly with fine emery cloth or steel wool, until the surface shines. Less satisfactory external ground connections may be made (in the USA anyway) to a #10-24x1.5" screw or a #10-32x1.5" screw that you have pushed into the small round ground-pin on a 120 VAC outlet. DON'T USE THE WALL OUTLET GROUND UNLESS YOU KNOW *exactly* WHAT YOU ARE DOING AND YOU HAVE VERIFIED THAT THE OUTLET HAS BEEN WIRED CORRECTLY. The diagram below is meant to represent a 120-VAC, 60-Hz, grounded outlet like those used in all but the oldest house wiring in the USA and elsewhere. The outlet has two parallel openings. Although the parallel openings are of roughly the same size, it can be seen that one of the parallel openings, the one shown on your left in the diagram, is slightly longer than the other one. The outlet has a third opening, the lowest one on the diagram, that is shaped differently and is smaller than the other two. AC Power Socket ________________ / \ | | | || | Larger parallel | || || | Smaller parallel opening | || || | opening (AC-return) | || || | (117-VAC) | | | () | Smallest opening | | (ground) \________________/ If the outlet was wired properly, the connector behind the smaller parallel opening is wired to the 117-VAC bus, the connector behind the larger parallel opening is wired to the AC-return bus, and the connector behind the smallest opening is wired to the house ground. Before you make a ground connection to the smallest opening, the outlet should be tested. A simple way to test the outlet, is to plug an AC-outlet Analyzer, Radio Shack 22-101 (or equivalent) into the outlet. READ AND FOLLOW ALL OF THE INSTRUCTIONS AND SAFETY MATERIAL THAT COME WITH THE OUTLET ANALYZER. If the outlet does not pass the test, do not make the ground connection. 4. A convenient length of wire (insulated or un-insulated), weighted with a washer or two, and dropped out of a convenient window. (A length of fine magnet wire (Radio Shack 278-1345) used this way might be a reasonable "invisible" antenna for apartment dwellers.) Try this with and without a ground. OUTDOOR ANTENNAS SHOULD BE DISCONNECTED AND GROUNDED WHEN NOT IN USE. NEVER USE AN OUTDOOR ANTENNA WHEN THERE IS A LIKELIHOOD OF LIGHTENING IN THE AREA. NEVER RUN AN OUTDOOR ANTENNA WHERE THERE IS A POSSIBILITY THAT IT MAY SWAY INTO A POWER LINE OR FALL ONTO A POWER LINE. 5. If you want to try an indoor amplified antenna, consider Radio Shack's #20-280, placed near a window. Ask about Radio Shack's return policy. Radio Shack's antenna is inexpensive (compared to others), and if it doesn't work for you, you will know about taking it back. 6. An end fed horizontal outdoor length of wire, used with a ground (see 3 above). Radio Shack sells a reasonably priced kit (278-758) with wire, insulators, and a window feedthrough. The wire can be any convenient length, or you can research the project ("Build Your Own Shortwave Antennas" by Yoder, is available from Grove Enterprises and others). OUTDOOR ANTENNAS SHOULD BE DISCONNECTED AND GROUNDED WHEN NOT IN USE. NEVER USE AN OUTDOOR ANTENNA WHEN THERE IS A LIKELIHOOD OF LIGHTENING IN THE AREA. NEVER RUN AN OUTDOOR ANTENNA OVER A POWER LINE. NEVER RUN AN OUTDOOR ANTENNA WHERE THERE IS A POSSIBILITY THAT IT MAY SWAY INTO A POWER LINE OR FALL ONTO A POWER LINE. 7. If your receiver seems to perform worse with the outdoor antenna than without it, you may want to consider using either the LOCAL position of the receiver's LOCAL/DX sensitivity switch, an external attenuator, a filter, or a preselector between your antenna lead and the antenna plug. Please be assured that I do not work for Radio Shack, MT, or Grove Enterprises. My only interest in Radio Shack or Grove is as a customer. My only interest in MT is as a subscriber.
This article was last updated on 12 August 1997.If you have any questions, feel free to Email me firstname.lastname@example.org . I'll do my best to confuse you completely (:-). (Comments or corrections also are welcome.)