Harry Bloomfield presented the following explanation :
Look up a 555 timer IC oscillator circuit. From memory they will easily run
up to 300Khz, then just connect your cable to the 555's output. Trace it with
a small radio tuned to 300khz.

http://www2.produktinfo.conrad.com/d...1-en-NE555.pdf

Only upto 100KhZ, sorry.

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Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk