Here is a neat Sniffer designed by Don, KF6GQ. It produces an audible tone which rises in frequency as the signal gets stronger. It uses 5 transistors and a 555 timer IC.
For a 1 Watt transmitter, sniffing range is about 225 feet using a 3 element Quad beam, or about 100 feet with a 1/4 wave spike antenna.
The Zero Adjust pot is used to set the tone frequency when there is no RF. With knob, field adjustable.
The Sensitivity Adjustment pot is used to control how much signal is required to produce the maximum tone frequency. With knob, field adjustable.
L1 = 5 turns, 1/4 inch form tapped at 1.5 turns. (For 2 meters)
Ct = Small RF trimmer capacitor, adjustable over about 5 to 45 pFd. Not critical. Screwdriver adjustment is fine.
Q1 & Q4 = 2N5457 (silicon J-FET)
Q2 & Q3 = 2N3904 (silicon NPN)
Q5 = 2N3906 (silicon PNP)
NOTE: Just about any small-signal silicon transistor of the same general type as specified should work.
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Down load as a GIF
Image. Its name is ToneSnif.GIF.
George (Russ) Andrews, K6BMG BMG Engineering, Inc. 9935 Garibaldi Avenue Temple City, CA 91780 USA Phone: 1(626)285-6963 FAX: 1(626)285-1684 (dedicated line, automatic) Web: http://members.aol.com/bmgenginc (10 Mar 1996) Send E-mail to grandrews@aol.com. (A message window will open.)
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