fm telephone transmitter[from electronics-lab]

[aimans]

hi, i have posted a thread on electronics-lab.com about an fm telephone transmitter not working, but the site has been down for the past few days, so i am posting it here, i hope it aint against the rules[yeah yeah i read em]

hi audioguru, here are the voltages of the phone line,

 

[audioguru]

Please post the schematic of the transmitter here. I can't remember if it is from Tony Van Roon or from Aaron Cake.

Is the measured 6.3V voltage the supply for the transmitter?
Is the transmitter wired in series with the phone?
Is the transmitter wired so that it is not destroyed by the ringing voltage?

 

[aimans]

Please post the schematic of the transmitter here. I can't remember if it is from Tony Van Roon or from Aaron Cake.

Is the measured 6.3V voltage the supply for the transmitter?
Is the transmitter wired in series with the phone?
Is the transmitter wired so that it is not destroyed by the ringing voltage?

no all the above measured voltages are with the telephone only without the transmitter being connected in series, should i measure them with the transmitter connected as well?

 

[aimans]

i connect the transmitter and then check the p.d then how do i know this is the correct voltage as my transmitter aint workin?

 

[audioguru]

If the circuit uses the correct parts and is made on a small pcb then it should work if its supply voltage is 3V or more.

 

[Hero999]

How have you assembled it?

It won't work on a breadboard.

Veroboard is alright but it needs to be as small as possoble and all leads need to be kept short.

For best results I would recommend etching a PCB.

 

[aimans]

i dont like breadboards, used a PCB- made it myself, all the stuff is fine, i just replaced one of the transistors [NTE123A with BC547],