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  1. walid1

    The capacitance of the varicap

    The varicap is a special diode that which changes its capacity according to DC voltage applied to it in reverse manner, that is when high DC => low capacitance and vice versa, I think this is OK. Now, looking to Fig.varicap (FROM: http://hem.passagen.se/communication/bug_rf.html), the varicap...
  2. walid1

    MIC coupling capacitor

    In Fig.MIC cap (part of FM Tx from http://hem.passagen.se/communication/bug_rf.html) below you can see the MIC connected to 100nF cap. I Know that 100nF value is not critical and I may use say 10uF, but to what level this value is not critical? What happen if i use a 4700uF or 1pF, please...
  3. walid1

    Air coils winding

    in many circuits there is an air coil, they told you that it is say 0.1 uH and also told you number of turns you must made and the former diameter and if this close wound or loose. If i try different values to achieve the same 0.1 uH using some formula, is then this coil operate ok as the...
  4. walid1

    50 ohm antenna

    i read this frequently, how I know that this antenna is 50 ohm, or how i can made a 50 ohm antenna, what the theory behind this. If it is a transmitter antenna and the transmitter operate at 50 MHz Fm what is the optimum length of this antenna to be 50 ohm. What the length if the freq. = 100...
  5. walid1

    10kHz FM modulation

    When I read this statement I understood that if the carrier signal is say 100MHz it will be shifted to 100.01 MHz up and 99.99 MHz down, is this true? Thanks.
  6. walid1

    Dots in transformer symbols

    i see often dots in transformer symbols, how these dots. How can I determine these dots practically on a real transformer. Thanks Walid.
  7. walid1

    GREAT CL8867B-A

    please I want a datasheets for CL8867B-A  it is used in cordless telephone, thanks
  8. walid1

    Power transformer winding

    8) Since long time I search about formulas used in winding a new transformer such that determining core area, primary and secondary number of turns and wire diameter etec Please if you Know them tell me. thanks WALID
  9. walid1

    IF transformers

    How can I identify IF transformers like this one: 002 0070 P0N2 this is what written at its outside can. I put these numbers in google for search, the results are nothing. can ay one help me please I want to know everything about it like i/p and o/p impedances, turns ratio, ...etec thanks...
  10. walid1

    Where can I Find

    Please where can I Find service manuals of cordless telephoes like GREAT FCC ID: A7PCS8100DS Manufactured in TAIWAN R.O.C. beleive me I need it. thanks, walid.
  11. walid1

    Wireless telephones

    Please I want anything about Wireless telephones, how they work, block digrams, schematic...anything. I have to understand this subject. thank you all for ay help.
  12. walid1

    Audio Transformer

    i have many Audio Transformer from my scrap, there is no part no., no spcification or anything to identify it. i want to use them in audio circuits, but i want to made some experiments to make an initial idea about them, i kow they are consista of a primary and secondary coils, the primary has...
  13. walid1

    Like resistors coils

    I have many of these coils shown in the figure below, the looks like a resistor and have the same colored circle to identify its value, but i cant know is this value in pico H,nano H, uH .... the upper one in the image is brown black black then silver, i think this is 10 xxH with 20% tolerance...
  14. walid1

    LED FLASHER

    This circuit from http://www.uoguelph.ca/~antoon/circ/flash2.htm is a led flasher, my question is what is its frequency, write the expression used to calculate it? at what maximum freq it can operate? thanks
  15. walid1

    What is a piezo 82dB

    can i relace it with a 10 watt ordinary speaker to make a pest repeller. thanks.
  16. walid1

    MIC & Antenna module

    If I want to simulate the circuit shown in Fig.FM01 using pspice, and I want to module the mic and putting an ac sig source in its place. what are these values representing a human voice: 1- Peak to peak amplitude 2- Rs - source resistance 3 frequency i think it is between 300 to 3400 Hz i...
  17. walid1

    MIC & Antenna module

    If I want to simulate the circuit shown in Fig.FM01 using pspice, and I want to module the mic and putting an ac sig source in its place. what are these values representing a human voice: 1- Peak to peak amplitude 2- Rs - source resistance 3 frequency i think it is between 300 to 3400 Hz i...
  18. walid1

    Design using Pspice

    When one uses Pspice software to primarily check his simple design before construction, what points should he take in account before transferring to real life circuit? How much the simulation be far from the real circuit? Thanks.
  19. walid1

    Early voltage determination

    When someone want to make a design using a BJT as amplifier, he needs to determine the early voltage of that BJT. How one determine it, or are there any standard approximations of it? Thanks.
  20. walid1

    Beta of the BJT

    All of us know that beta of any BJT is not constant value and it is change depending on temperature and biasing conditions...etc. L know three methods to primarily determine its value: 1- data sheets (not always available) 2- measuring it using hfe function of a digital multimeter 3- put the...
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