figure8 Rx

[green]

Some pictures. Coils taped to pieces cut from Elmer's foam board(5mm thick). Pickup coil slides on wood dowel marked at 1inch increments.

Tested a single 8inch coil. At 2, 4 and 6inches about 2 times the signal, double coil same polarity. Close to the same signal at 12inch distance.

Thinking mono Rx would have a higher signal than a figure8 Rx opposite phase. Was going to compare noise, figure8 vs mono coil(S/N is what's important). First I made a square wave oscillator with a TLC555 with a 40k resistor to output in series with 10R to -supply(uses a separate 9V battery)to check amplifier response. Connected Rx input across 10R resistor(battery 8.7V). Expected higher frequency response with the LM4562. What should the frequency response be? Can compare coil noise but wondering if I'm doing something wrong?

[green]

Thinking mono Rx would have a higher signal than a figure8 Rx opposite phase. Was going to compare noise, figure8 vs mono coil(S/N is what's important). First I made a square wave oscillator with a TLC555 with a 40k resistor to output in series with 10R to -supply(uses a separate 9V battery)to check amplifier response. Connected Rx input across 10R resistor(battery 8.7V). Expected higher frequency response with the LM4562. What should the frequency response be? Can compare coil noise but wondering if I'm doing something wrong?

Tried the amplifier circuit with spice. Used a LT6234(60MHz)instead of LM4562(55MHz). Step flattens at about .5us instead of 3us I get with the MPP using a LM4562. Any thoughts what I might be doing wrong? Maybe a fake chip?

[6666]

thanks Green, using dodgy wifi, later

[green]

Wondering if MPP step response with LM4562 should be shorter than the 3us to flatten reply #16. Tried another experiment. Soldered a 100R resistor across the 1000R input resistor and a 4000R resistor across the 33k fdbk resistor. Faster response. One possibility, circuit capacitance in the fdbk. Wouldn't think circuit capacitance would be enough to cause that much increase in step response. Appears LM4562 isn't fake. What other than circuit capacitance could be causing the slower step response?