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Posts posted by aimans

  1. If you are far from the telephone exchange then your off-hook voltage will be low enough to operate a single telephone. If the phone draws a high current and you are far from the exchange then your voltage will be too low to also power the bug transmitter.

    if that is the case then i can use a 9V battery to power the transmitter while connected to the phone line,

    what do you think about this battery thing, will it work?
  2. thanks a lot for the circuit, i will surely try it adn let you know, i hope it works as i am not sure whether LM2931 is available here, and then later try the phone transmitter, and i will try to post a better pic as i am at takin pictures

    i dont know if this is a stupid question or not but i'll ask as i have already asked naive ones before: is there any way your circuit can be converted into a phone transmitter? ::)

  3. yes i made it agian and failed again in this fm transmitter, this time i corrected most of my previuos KNOWN mistakes but nothin on the radio. just cannot figure out why, my friends say i need someone to teach me!

    this time i replaced Q2(2N3563) with BC547 and the other transistor is the same, didn't have 5.6pF so replaced it with 5.8pF, i dont think that is the problem though.

    i calculated the inductance of the coils according to the instructions given, and they wre not at all close to those mentioned in the instructions[at the bottom of the page http://www.uoguelph.ca/~antoon/circ/FMTelTx/telephon.html ], so i just made the coils as it was given  and not the values given,

    can someone help me in this thing i am very frustated with this phone transmitter, i tried them about 10 times but to no avail, someone please help me out here,

  4. after having a very unsuccessful time with FM transmitters using "wire" inductors and tunning capacitors, i am turning to crystal oscillators,

    so can any one tell me whether a crystal oscillator can be used for audio transmission like an FM transmitter? i have 2 crystal oscillators of 27.xxxMHz from an R/C toy, so is frequency the only difference or there are other draw backs?? and why are there not many audio transmissions on low frequency?

    too many question ehh, can you help out???

  5. i soldered the replacements with the correct PINs i kept that in mind had their datasheets while soldering them. i also didnot use "tinned copper" wire as the site told[i thought that it will not make a lot of difference] ami correct??

    I think the parts are too far apart on your PCB which causes high stray capacitance and inductance.

    The project has a PCB that is much smaller than yours. Why not make it exactly the same?

    sure i will make it like the original nice and small, i made mine in a hurry,

  6. AC current through wire that passes through a unknown flux field gives you the frequency based on the number of loops you see?? I've never heard of such a thing... please explain further!!

    Are you sure your just not seeing the resonant frequency of the wire... like a guitar string?

    here the below files may espolain what i was trying to do, the site does not allow .swf files so i put em in a zip folder,

  7. If you short circuit a voltage supply without something to limit the current then it gets too hot. Hopefully it is a fuse that gets too hot and it blows to prevent a fire.
    Keep away from electrical things until you learn the basics.

    The mains frequency in my country is 60Hz. It is 50Hz in some other countries. You can't change it. It is easily measured with a frequency counter. My multimeter has a very accurate frequency counter.

    The harmonics are caused by distortion, not by length and not by weight.

    i knew these methods as well, but wanted to implement my theory stuff.

    and the harmonics[or loops] in  the stationary wave were caused by keeping a horse shoe magnet at the middle of the wire, so that the wire was inside a perpendicular magnetic field. and when i passed the current from the transformer it vibrated with 3 loops or harmonics.

    the loops which are formed in the stationary wave are linked to the length of the wire and the tension in it[hanged mass from a pulley], the equation for the  frequency of the fundamental mode in a stretched wire is below:

    T=tension in wire
  8. i was trying to determine the frequency of the a.c[ i know it is about 50-60Hz] but wanted to find it myself, and also to find the number of harmonics in a fixed length and mass[i got upto the 3rd harmonic at max. with .9m and .15kg]so i simply shorted it out, the thing got so hot that the plastic on which the windings were made melted, even though the room temperature was close to 0` Celcius.

  9. i was using a 1500mA, 12V transformer to find the resonance frequency of a copper wire. but the transformer was getting hot too quickly, within 15mins of its running it was too hot to touch. is it because the circuit was short circuited by directly connecting to the copper wire with nothing else? or is there a problem with the transformer?

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