Please could someone advise me where I can get a kit or even instructions to
build a device that emits a very high frequency 17.5-18.5 kHz tone.
18 kHz(+/-3%) is not VHF, not even technically ultrasonic.
I am not an experienced electronics expert but could manage a simple
project.
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`-------------------------------------------------------------'
S E M I - P R E C I S I O N D O G A N N O Y E R
+6V -+------------------+----------+--
| | |
R1 `-[100Ω]-. . . . .|. . . . |
\ | . VCC(8) . |
/ | . . |
\<---------+---DIS(7) RES(4)----'
2K / . NE555 . |
\ +----------TH(6) OUT3(4)--------+--------|
R2 / | . . | | piezo speaker
| +----------TR(2) CV(5)--. | .---|
| | . . | | | |
+---+ . GND(1) . | | |
| . . . .|. . . . | | |
| | | `----|---[10KΩ]---+
C1 === | | | |
| 22nF | === 10nF +---[1KΩ]----+---->
| NP0 | | | TO 3.5mm plug
0V -+----------------+--------+----------+----------------->
the chip should be LM555 or NE555, C1 should be an NP0 ceramic type
R2 should be a multi-turn trimpot.
build this then plug it into your computer's line in jack and view
the wave on a program like audacity adjust R2 to get as close to
18Khz as you can.
Bye.
Jasen