An improved Radiometer Ferret

[Randy Seden]

Found this design for a phase detector that only uses 1 IC and two Transistors that does the same thing that the Radiometer Ferret did with the exception of no audio output-meter only. See attached images. I've wired up the circuit and just have to wind the coil (that's another improvement over the R.F., this only uses 1 coil). It appears from the guys field test that 565PLL does a much more effiecient job than all those components in the R.F design also,as he was able to detect metal 2.46feet away using a 2" coil at 1KHZ. Am taking this out to the goldfields in the Mojave Desert, where the red dirt plays havoc with VLF detectors. I had brought home 2 1/2 bucketfulls of this soil to wet process last month and now I can use it to calibrate the meter with sample gold nuggets. Will let you know how it turns out. I plan on running it at 20KHZ for the smaller gold.

Randy





Phase metal detector text





Phase metal detector schematic

[Carl]

Re: An improved Radiometer Ferret

This was published in Electronics World in 1992. I recently made a clean copy and since I have permission from the publisher I need to get it posted.

I have a few 565's so I will also build it up. Talk about simple! But I'll bet the claimed distance is for a car, not a coin. Still it would probably be a good circuit for a coin probe. Thanks for posting it!

[Eric Foster]

Re: An improved Radiometer Ferret




Hi Randy and Carl,

Looks like this circuit has a bit of history. Schematic above is from the Signetics Phase Locked Loop Application Manual 1972.

Eric.

[Randy Seden]

Hey Carl, when ya going to post the 92' article?N/T

N/T