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  1. audioguru2

    Is it possible to build a tranceiver on am with mhz

    An ordinary AM radio operates from 540kHz to 1.6MHz. CB radios were AM in North America and operated at around 27MHz. Ham radio uses all kinds of modulation types and is on many MHz frequencies. Older wireless home phones used AM on MHz frequencies. Even airplanes and air traffic controllers use...
  2. audioguru2

    op-amp low frequency pulse generator

    No. When the comparator's output is at +9V, R3 pulls pin 3 to a positive voltage. When the output of the comparator is at -9V, R3 pulls pin 3 to a negative voltage. Actually, it is +3.0V and -3.0V because the output transistor of the comparator doesn't have an emitter-follower loss like opamps...
  3. audioguru2

    Latching comparator help

    Hi Mr. Heckles, A series resistor then a capacitor to ground would be a spike filter. It would delay an over-current sense.
  4. audioguru2

    how to find out the frequency of an amplifier

    Hi Indulis, You can look on the web for "an electrical model" of a speaker. Here is a real measurement of a typical woofer speaker that shows is resonance, without an enclosure that would raise its frequency.
  5. audioguru2

    current series feed back in amplfiers

    I don't care what the feedback is called in books. Your amp transistor is operating in class-C without any bias current. Its tiny emitter capacitor allows it to amplify only high frequencies. Its load has such a low resistance that its gain is squashed.
  6. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Tedy, Great! You fixed it. ;D
  7. audioguru2

    how to find out the frequency of an amplifier

    The frequency response will be flat (no attenuation) from 100Hz to a high frequency. The response below 100Hz will gradually drop until it is -3dB at 20Hz. A rather large output cap and resulting very low cutoff frequency was chosen to allow the very low impedance of the amplifier's output to...
  8. audioguru2

    op-amp low frequency pulse generator

    Hi Walid, An LM393 isn't an opamp, it is a dual comparator. A comparator oscillates at a high frequency if it has negative feedback. Its pin 4 needs to be grounded. It is a Schmitt-trigger oscillator. Its pin 5 is pulled up to about +2.7V and down to about -2.7V when the output toggles. The...
  9. audioguru2

    0-30 Vdc Stabilized Power Supply

    Well, there isn't much remaining: R2 or C2 are open or the wrong value. D5 or D6 not working or backwards. Shorted diode in the bridge rectifier. Broken trace or shorted traces on the pcb. ???
  10. audioguru2

    Teleconferencing please help

    Hi Shaiq, Most telephones have only a single phone line. They can't put one call on hold then call someone else. They use only two wires. Then the transistor isn't necessary. Just connect phone #1 with its own phone line to one switch, and a second phone with its own phone line to the switch on...
  11. audioguru2

    Windshield Washer Fluid Heater

    Here they use a lot of salt on the roads following a snowstorm. I could use 4 liters of squirt just on a single drive across the city. The computer doesn't say how much remains. Sure it runs dry! Just the metre or two of hose from the tank to the blades takes quite a long time to refill. Do...
  12. audioguru2

    how to find out the frequency of an amplifier

    Hi Indulis, At about 5 times the frequency where the capacitor's reactance equals the speaker's impedance, it is no longer a highpass filter and the small increase of the speaker's impedance with rising frequency due to its inductance is negegible. There isn't gain in a capacitive coupled...
  13. audioguru2

    Latching comparator help

    Hi Mr. Heckles, Try these bananas:
  14. audioguru2

    Windshield Washer Fluid Heater

    When the tank runs dry, how long will it take the pump to refill 30 feet of hose? A couple of hours?
  15. audioguru2

    About analog Multiplier

    I made some simple audio scramblers and descramblers using a balanced modulator IC MC1496 for a wireless boardroom tele-conferencing system. It was suppressed carrier, single sideband and it inverted frequencies. High frequencies were low and low frequencies were high. The output sounded weird...
  16. audioguru2

    help about this supply

    Hi Ante, Maybe the circuit was designed before the simple and excellent LM317 was invented. Maybe LM317's weren't available over there. My variable voltage power supply has an LM317 in a simple circuit. Its performance doesn't "just give good results", its performance is perfect. ;D Of course...
  17. audioguru2

    how to find out the frequency of an amplifier

    Hi Shaiq, In my last post I said to calculate the reactance of a coupling cap with its load at the frequency you select. Our hearing extends down to 20Hz. Your speaker is 8 ohms. The reactance of a 1000uF cap is 8 ohms at 20 Hz. The frequency response will drop -3dB at 20 Hz and be flat down to...
  18. audioguru2

    Windshield Washer Fluid Heater

    When they tested the heater they said it got warm. That's not good enough in winter. The spec's say a high resistance and a high power. Impossible.
  19. audioguru2

    Input signal for LM3915. need help.

    My new Sound Level Indicator project works perfectly and is here: http://www.electronics-lab.com/projects/motor_light/009/index.html
  20. audioguru2

    Is it possible to build a tranceiver on am with mhz

    Your question doesn't make sense.
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