Search results

Search Forums New Posts
  1. walid1

    Very low power FM transmitter discussion

    Hi audioguru you confused me, is the transistor operate in common emitter or common base? and, if L = 0.2uH what is the carrier frequency? thanks.
  2. walid1

    Very low power FM transmitter discussion

    I'm asking the entire world what I learn from this picture... The picture provided her is from: http://www.rf.fcpages.com/Fm-spy.htm If you go to this page you will find only this picture without any reliable comment. You find similar pages in more than 90% of the web. They only told you that...
  3. walid1

    Hum in the incoming signal

    Reply to audioguru: First of all welcome, I wait for your reply you are my great teacher… (1) You said: “Your audio cable carries a low level signal and hopefully is electrostatically shielded.” What you mean by shield, is this shield which we find inside any antenna cable or you mean that to...
  4. walid1

    Hum in the incoming signal

    Reply to Bjorn: You ask: “I'm not sure what you meant when you say that you take the power from you generator. Are you running two power systems at the same time?” No most of the time we take the power from the local electric company, but when the company cut off feeding electricity then we use...
  5. walid1

    please..........please..........please

    Hi Hany, These sites are very good but long text you must be patient read it carefully ask about what you can’t understand: 1) http://www.opamp-electronics.com/tutorials/ 2) http://www.kpsec.freeuk.com/analogue.htm 3) http://www.faqs.org/docs/electric/AC/AC_3.html Please note that you may go to...
  6. walid1

    Hum in the incoming signal

    Hi, I see that we limit the problem in two things: (1) (a) Grounding problem and I must check this. Can anybody tell me the fastest and best method to check this, what instrument may I use and what acceptable reading should I looking for, how to decide that ground is OK or need to strengthening...
  7. walid1

    Hum in the incoming signal

    please I need more info..... why hum increases when the main AC power is taken from our generator. It is true, there is power lines in parallel to signal lines in the same place, is this one of the causes producing hum. I notice that when toutching the receiver  outside body you feel some...
  8. walid1

    Hum in the incoming signal

    Hi, thank you all for your responds, first of all I want to tell you that the hum in audio is 50Hz and in video is two bars scanning the monitor screen from top to bottom or from bottom to top, the scanning is very slowly. Mr. Bjorn said that: “Your equipment is connected so it produces a...
  9. walid1

    Hum in the incoming signal

    In Palestinian satellite channel when a signal come to the continuity studio from outside, there is a hum on it (hum in video and audio), and this is clearly obvious when we take the main electric power from our generator, but the internal signals from the studio (cameras and VTRs ....) are very...
  10. walid1

    3dB point or pole

    I read this: "Present-day operational amplifiers are comprised of multiple stages, each of which has a 3dB point or pole associated with it." what the meaning of [a 3dB point or pole]? thanks
  11. walid1

    BASIC FEEDBACK THEORY QUESTION

    I read this: "The ideal parameters are never fully realized but they present a very convenient method for the preliminary analysis of circuitry. So important are these ideal definitions that they are repeated here. The ideal amplifier possesses 1. Infinite gain 2. Infinite input impedance 3...
  12. walid1

    OFFSET NULL ADJUSTMENT

    hi all of you i read this (look at Fig.1) from http://www.uoguelph.ca/~antoon/gadgets/741/741.html but idon't know what is OFFSET null, what the advantages and disadvantages if i care to it or not? thanks.
  13. walid1

    telephone related question #4

    Hi audioguru Your answer above needs more explanation in the following points: (1) I'm sure that I read some where that the tel. designers make part of MIC sig. fed back to speaker network and they do so to prevent the user of tel. from shouting. This is true, if you can't hear yourself you may...
  14. walid1

    C_B transistor impedance matching

    No No No you all not understand me at all, you all say absolute talk, the net is full of such talk, I ask obviousness question that: I need a theoretical information about designing an impedance matching circuit using a common base transistor configuration. The transistor is PNP small signal...
  15. walid1

    telephone related question #4

    As shown in the schematic, the MIC signal travel from MIC to C7 (0.04uF) to the base of Q4 for pre amplification. I read somewhere that part of MIC sig is fed back to the speaker driver (Q5) so that the user can hear himself, if they don't do this the user shouting. Now is this part of  MIC sig...
  16. walid1

    telephone related question #4

    Very good, this is what i looking for, floating i understand it, but please tell me: (1) What happen when it turned on. (2) What the difference between a PNP transistor's collector, and NPN one. (3)Are you mean that the MIC acts as a resistor and the voltage drop across it =2.4Vdc  thanks
  17. walid1

    telephone related question #4

    MIC has 2 pins one grounded (the -ve) and the other connected through a resistor to the power supply, here in our circuit, the +ve MIC terminal is connected through R17 + R15 to 7.4 Vdc. To MUTE this MIC, the +ve terminal of it should connected to Ground, if it connected to 2.4Vdc as shown in...
  18. walid1

    telephone related question #4

    hi, i'm comig back ..... i love you all my question is : All DTMF ICs used in telephone circuits have pin called MUTE (pin 13), in HM9102 IC datasheet i read the following "This output is an inverter normally at low state when there is no key entry. During outdialing it changes to high state...
  19. walid1

    Telephone related question #3

    Hi Mr. audioguru, When I say "Please I want a direct answers" I don't mean a brief answers, in short you must know that you and this site is the only source of information for me. Now lets go.... Question 1: Why always PNP and not NPN? Your answer: To make a positive supply voltage. An NPN...
  20. walid1

    telephone related question

    From all of this discussion with Mr. audioguru about telephone diodes I can tell others that in general any diode in conduction state(forward bias) acts as a very small resistance and it can pass a small signal in two way direction, in other word look you can look at this diode as a small...
Top