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  1. walid1

    Audioguru FM Tx

    Hi audioguru yes, it is very good point. i experiment with 3 mics, applying 9 volt dc to each and measure the drawn current with 1k then 10k ohm resistors. i had the resuls shown in the table below. look at it, changing R from 10K to 1K increasing the current only small amount, it is really a...
  2. walid1

    Audioguru FM Tx

    Hi guru thank u very much lets discuss it: 1- is the mic is a constant current source that its current not effected by changes in R1 value. or this current increased by decreasing R1 value. 2- the sensivity of mic is increased when more current pass through it> 3-when mic circuit driving a...
  3. walid1

    Audioguru FM Tx

    Hi audioguru after my last question, another friends take the subject to a more complex corner, so i back it to its simplist form again. In our discussion about R1 (=10K) we conclude that most of mics drawing 0.5mA and have 1/2 vcc across them so R1 must be 5K or 4.7K, and you told me that...
  4. walid1

    a very simple FM Tx

    Hi guru I feel that i not understand what you want to say. Lets analyze that statement: I assume that VE = 3v VB = 3.7v positive feedback changes the emitter voltage to say 4 v so VB = 4.7v now what that cap do to maintain VB to 3.7 v thank u guru
  5. walid1

    a very simple FM Tx

    Hi guru why the circuit probably won't oscillate, can you please, explain this point more. What would u do to improve the matching between o/p and antenna? beta = 200, are u guess it or depend on some source or you consider any general purpose transistor's beta as approx 200. also you calculate...
  6. walid1

    a very simple FM Tx

    Hi guru ok, i agree my circuit did not using a varactor diode, there is no varactor diode i think that a p-n junction do this, is this true and how?
  7. walid1

    a very simple FM Tx

    i read it but i not understand any thing it is not as i expect can u guru point me to another article more close to what i need can u help me in understanding carfully how this vco operate thank u
  8. walid1

    a very simple FM Tx

    Hi guru i read carefull your last reply but it was not sufficient to make me understand so, i now reading this doc. http://www.maxim-ic.com/appnotes.cfm/appnote_number/2032 may it help me then i'll back to u to finish this hard subject thank u guru
  9. walid1

    a very simple FM Tx

    Thank you guru u are a good man why it need to be a common-base, what would be happen if we remove this 1n cap. I know that
  10. walid1

    a very simple FM Tx

    the following FM circuit I have tree questions: 1- what the function of the 1 n cap 2-why tapping the coil, why not connecting the antenna directly to the collector 3-what the function of the 1.8p cap, and why it is so small thanx
  11. walid1

    TV's and monitors maintainance and repair Forum

    i want a community (forum) like this electronic-lab community, where they discuss about  TV's and monitors maintainance and repair thank you very much
  12. walid1

    SMP power supply

    it is not difficult questions, i need answers ................ wait walid
  13. walid1

    BJT biasing formulas

    good discussion
  14. walid1

    SMP power supply

    no reply thanx
  15. walid1

    a low value wattage resistance

    hi guru we all know that resistors are used to limit current to some value can a 0.5 ohm resistor limit current and to what level secondly: why it so big 10 watt, what if i use a 0.5 watt regular resitors no no, i'll ask my question another way: what exactly i want to know that: what should i...
  16. walid1

    a low value wattage resistance

    hi in many many circuits u faced a wattage resistance for example in a PC monitor i see a 1 ohm 5 watt and in a low cost inverter in our project section you can see a 6 0.5 ohm 10 watt also in many car batt charger you find one directly before the batt why this resistance can i replace it with...
  17. walid1

    SMP power supply

    Hi In the Fig shown below is the input part of a switching mode ps as most of us know the 220VAC is connected directly to the rectifer (4 diodes) through a filtering network the rectifier o/p is about 310VDC in some SMPS there is a one main filter capacitor 400v 220uF or so in another there are...
  18. walid1

    What the meaning of .....

    In fact you make it very clear thank u all very much
  19. walid1

    What the meaning of .....

    What the meaning of hybrid i read the following in the STR50330 datasheets: Hybrid IC voltage regulator thanx
  20. walid1

    Infrared Remote Control

    thank you guru very much you really helped me
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