Hello, I am looking for an electric schematic of a telephonic Tone and Probe.
Professional instrumet are like this:
Thank you Umberto
Amazon has wire tracer kits for around $16. I got one and it's interesting. You can hear all sorts of e-fields.
Il giorno venerdì 15 settembre 2023 alle 15:01:44 UTC+2 John Larkin ha scritto:
My purpose was to design one, anyway thanks for the indication.
Bartolomeo Pestalozzi snipped-for-privacy@gmail.com Wrote in message:r
You can drive a reversed biased diode with a 555 running s a frequency in the audio band. This will create a nice broad spectrum modulated hash. Then use a lm386 audio amp a nd attach the input to a short antenna probe as the reciever. I used this setup for many years, and it always works.
Cheers Cheers
The probe should be very high impedance. Use a jfet or a cmos opamp and a lot of resistance to ground.
Oh, just a cap to the probe tip. The lm386 has 28db of gain. If it squeals when you touch the probe tip you got gain.
Cheers
Yikes. LM386 is an ancient bipolar part with < 50K input impedance. Given, say, a 5 pF antenna/probe, the highpass corner frequency is about 300 KHz.
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