namzer0

well ok, the circuit works! I can hear something when I rub the mic with my finger and I can hear my voice... I just can't make it stable enough to work smoothly. seems like every movement does something on the whole circuit... (a bad PCB board layout?) when I leave it without touching anything, nothing, like its off. when I press on the board, sometimes its working...

I'll post again here after I wind up the new coils...

This is the one that Im using from http://en.wikipedia.org/wiki/Inductor#Inductance_formula or in simple: L=Mr(N^2*A/l)k k=1.26E-6 Mr=1(for air coils) N=turns A=area (4/3pi*r^2*l) meters, so for mm, I use the suffix E-3 (ex. 1mm; 1E-3) EDIT: A= pi*r^2*l no 4/3

I just figured it out lately... came up with 2 turns, same radius (3mm), 5mm long, but only at 0.379uH(379nH). need some estimates to arrive at 150nH... haven't soldered it yet. here are some pics if you dont mind the coil here is my antenna the whole thing [img width=680 height=510]' alt='' class='ipsImage' > back parts [img width=680 height=510]' alt='' class='ipsImage' > view these on a digital camera, its brighter

I built it on a 2in PCB, no enclosure yet. Im feeding the mic with an mp4 player input. (mp4 speaker beside the mic. for detecting purposes only) The antenna is a #22 awg coil(2 layers of 1in long) I appreciate the 150nH suggestion... but is there a way to narrow the frequency(temporarily) to 90-100Mhz? just to be sure, I'll wind up the 150nH coil later today. Thanks

I build the circuit here: http://www.electronics-lab.com/projects/rf/030/index.html replaced the 5.6pF with 5pF wound my own air-inductor(4 turns wound on the inside of a pen... shows near 1uH) operating at 3V 2AA batteries just finished lately, and I'm having difficulty in tuning it into my radio(no sound even beside the tX) don't know whats wrong... the inductor, wrong formula/area? Maybe a soldering damage(overheat??)? I have a multitester(Volts Ohms Amps only) I'll appreciate if someone will guide me on this. :'( :'( :'(