Hello,

I am missing the inverter between the control lines of the 4066 gates.
Also the control signals are direct coupled and not via a capacitor.
I also recommended to have about 50 % duty cycle as with the hysteretic oscillator as in the following link:
http://forum.allaboutcircuits.com/showthread.php?t=15342

Bertus

 

another way to do it is like the elf recievers. microphone into mixer, 5 mhz osc into mixer, mixer out to decent short wave reciever. recieve frequency -5 mhz = bat frequency. 5.040mhz = 40 khz bat. search for elf convertor for details.

 

I see the 47 ohm collector resistor made it in there. Unfortunately, as shown it will not balance the gains as intended because of the 100 uF decoupling cap. The idea here is that for true differential outputs from one transistor, the impedances of the collector and emitter must be different because their currents are different by the amount of base current flowing through the emitter. 1% is an estimate. Your beta may vary. No warranties expressed or implied. Discount offer not valid in Michigan.

ak

 

Are you talking about R101? The only changes I made to the schematic itself was putting the 4066 in and wiring it according to joey's diagram.

All of the rest is the same.

 

...and wiring it according to joey's diagram.

No. I think you are using Bertus' diagram.

 

No. I think you are using Bertus' diagram.

so I am.....so I am.

 

and yet another way to do it, high performance sound cards go above 40 kHz, just use a laptop with software to display the spectrum of the bat signals.

 

Not a bad idea but I am looking for a portable, simple device like a bat detector, but much cheaper than the models I've seen.

I want to possibly market this product to rat owners, and 90% of them wouldn't be capable of even assembling a kit, so using a soundcard is out of the question for this particular topic anyway.