Super BFO

[Shawkins]

I looked at the diagram again and zoomed out to see the eight 2k7’s to the right with “damping resistor determined by coil 250 ohm to 600 ohm”. I might try a larger value

[6666]

Here is a very short test video of Super BFO1.
Its scorching in the Aussie sun today, but tested some Aussie coins, USA coins, steel bottle caps
you can tell the difference with a steel bottle cap.

http://youtu.be/3GG-OS_bEE0

[Shawkins]

That sound quite different to the one I made, the "idle" tone of mine is a much lower frequency and is a constant stable tone until a target is detected. I tried variations in the damping resistance but all I got was a loss in depth and sensitivity, although the idle tone changed. I think my coil has too much capacitance, I’ll try an unshielded coil with lower capacitance as a quick experiment. Although I’m getting a bit frustrated with this design – for the component count I expected more, and until I learn to program I think this is a dead end for me.

[6666]

Hi interesting about your idle tone, mine alters quite a bit, as per video, still needs more testing.

[6666]

Today I tried a super sized coil its 17"x9" rectangle with round ends, I wound this coil for a pi project, but put more turns on it to measure 540uH, so I could try it on this machine first, the super bfo seems to like it, much better in air depth test.

[Tec]

I like the you-tube clip by the way

[6666]

Hi Tec
which is ground for this design + or - ?
thanks

[Tec]

Ground pin

Hi,

see attached - is the ground, the terminal next to - is also ground .
(Ground is in blue, in the image attached)

[6666]

Thanks Tec.