A For close-in tracking (DFing) of a wideband noise source, you need a receiver that is fairly high in frequency. The AM aircraft band at 120 MHz works well and inexpensive receivers can be found that cover it. Many of the H-Ts on the market today also include AM reception in that frequency range, so if you know someone who has bought an H-T in the last couple of years, ask them if it has AM aircraft and if they would be willing to help you track down the problem.
Quite a few portable shortwave receivers also have AM airband reception. Another alternative is a couple of portable receivers from Radio Shack that feature AM aircraft reception. Model 12-456 retails at $35 and model 12-615 (handheld) sells for $25. Although these receivers do not have coax connections, you can still use them by connecting the center conductor of the coax from your DFing antenna to the existing antenna with a clip lead. Connect the shield of the coax to a case screw. The mismatch will give you some attenuation, but it will be a useful setup nonetheless. You can find more information on hunting down power line RFI on the ARRL Web site at: http://www.arrl.org/tis/info/rfielec.html. Also, check out “A Line Noise ‘Sniffer’ That Works” by William Leavitt, W3AZ, in the September 1992 QST.
If you don’t have the issue you can get a photocopy of the article for $3 ($5 for nonmembers) by contacting the ARRL Technical Secretary at 860-594-0278; reprints@arrl.org.
W3AZ mounted an airband receiver in a shielded case as part of his line noise “sniffer.”
From QST February 2000
