Recent content by russlk2

  1. russlk2

    Please tell me the alternatives of these

    High frequency crystals are of the overtone type and will not oscillate at the correct frequency in that circuit, if it oscillates at all.
  2. russlk2

    Capacitor circuit design...

    I would forget the capacitor and find a solonoid coil, like used in a washing machine water control.  Get an iron rod from the local hardware store that will fit in the coil, an iron or brass washer that will also fit the rod.  When 110VAC is applied to the coil, the washer will be propelled up...
  3. russlk2

    Television safety (help)

    For safety, keep one hand in your pocket and wear rubber soled shoes or work on an insulated surface. The high voltage won't injure you but you could be injured when you jump back. If you have overheating components, you have to find the cause before replacing parts. Check leakage of filter...
  4. russlk2

    7805 overheat and Clock signal

    You think it is overheating? Put your finger on it. If you get burned it is too hot, if not, that is not your problem.
  5. russlk2

    LCR circuits

    You can't use the reactance as a plain number, you have to consider the phase angel. The current leads the voltage by 90 degrees in a capacitor and lags by 90 degrees in an inductor. The reactance of an inductor is given by Xl = 2*PI*f*L where PI=3.14162, f= frequency in Hz, L=inductance in...
  6. russlk2

    Transistor Audio Filter Design

    The gain of T1 is nominally RV1/R6, but there is negative feedback thru R2, so the computation is complex. The purpose of R6 is to stabelize the DC current and increase the input resistance of T1. The input resistance is rb+beta*R6. Probably around 4700 ohms. The input capacitor (100nF) is...
  7. russlk2

    TV Signal Amplifier circuit

    L2 resonates with C5 and C4 near the center of the TV band. A 75 ohm resistor would probably work as well. L1 is a "peaking coil". It is self resonant near the upper edge of the band and is there to raise the high frequency gain. You cannot put a pot in this circuit because the leads have to...
  8. russlk2

    Close range RF Locator

    The basic problem is that radio waves travel at 186,000 MILES per second, so 1/8 inch is such a small time you would be extending the state of the art several orders of magnitude if you got this idea to work.
  9. russlk2

    4W FM Transmitter

    mF means millifarad, but that is an error, it should be uF. The european style is to use , instead of. so it is 4.7uF. #18 wire is rather large and I would not space the turns, use close wound and at least 8 turns. The 4 turn inductor is .132uH if you use #18 wire, close wound.
  10. russlk2

    How Can I extend my FM transmitter range?

    Transmitting 30 watts without a license is probably highly illegal. A directional antenna can boost the signal without getting you in hot water. The ARRL antenna book is a good source of info.
  11. russlk2

    common mode rejection in audio transformers

    The result of a measurment will depend on how it is done, and the method should relate to the way is is going to be used. If the secondary is to be grounded, the measurement should be done that way. If the transformer includes a faraday shield, the common mode will be nil and hard to measure...
  12. russlk2

    Help with code transmission in RF or IF

    The RF is just the carrier, the DTMF tones will all ride on it. The receiver will seperate the tones using filters, each one identifying a bus. simple tones could be used because the probability of interference is low and signal to noise will be high.
  13. russlk2

    sensitive low frequency filter

    This circuit will provide the lowpass and adjustable gain:
  14. russlk2

    Help with 60 second stopwatch project

    There is not enuf information here: What is the source of time? What does the output look like?
  15. russlk2

    power vs. signal frequency

    The advantage of AC power is that you can transmit at high voltage and low current, for low loss, and transform back to low voltage and high current at the load. But, 15 VAC is not high enough to be efficient, why not send the power as DC? The signal coming back could be on an AC carrier, or...
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