BPNGUYEN

Hello every one; I would like to build a mosquitoes repeller. I did some researchs and come up with two promising circuits. One is use NE555 OpAm and can use 9 to 12V battery. The second circuit is use a phase locked loop (CMOS4047) wired as a 22kHZ osillator. The output is amplified by a pair of NPN transitors and drive a Motorola 3.25 inch Piezo. Current drain of this circuit is about 120mA and has to use an external power supply which is I don't realy like to do. >:( Do you have any recommend about this? Do you know at what frequency the mosquitoes hate the most? ??? :) Best regards Ben Nguyen