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  1. audioguru2

    Power Line Commucation Help Find Info

    The wires are only wires that can carry signals. The 60Hz power doesn't know or care if you add broadband to the wire. The broadband doesn't know or care if the wire also has 60Hz power. When you receive it you just add a filter to the line to block the 60Hz but pass the broadband.
  2. audioguru2

    time beeper

    When you are on the Time Keeper site, right-click your mouse on its address in your browser and left-click Copy. Then during your reply here just right-click your mouse on the page then left-click Paste. That's how to post a link that works. ;D
  3. audioguru2

    Power Line Commucation Help Find Info

    A pair of wires can carry many signals. The mains frequency and the high frequency carrier frequency. One pair of wire carries all the sounds of an entire orchestra to your speaker. One coax cable TV wire carries many channels to your TV. My cable TV coax cable even carries my high speed...
  4. audioguru2

    BJT biasing formulas

    I didn't "decide" to use a 10:1 ratio of divider current to base current. The -50%, +100% range of current gain and the temperature change of current gain "dictated" to use that ratio so that the transistor's DC operating point doesn't change too much with different transistors having the same...
  5. audioguru2

    BJT biasing formulas

    Hi Walid, 1) When you increased the value of R3 and R4 to 2k and 100 ohms, you should have also reduced their current. 15mA through 100 ohms produces 1.5V like you calculated, but 15mA through 2k is 30V. The battery is only 9V. Therefore the transistor is saturated with its emitter and collector...
  6. audioguru2

    3 way speaker system

    Hi Alun, The speakers shouldn't run into their mechanical limit if the enclosure is properly designed, until the momentary input power far exceeds their continuous max limit caused by heating. A sealed or completely open enclosure (mounted on a wall between rooms, speakers on a car shelf and...
  7. audioguru2

    BJT biasing formulas

    Hi Walid, The input impedance of the second stage is in parallel with the RC of the 1st stage, so an input impedance for the 2nd stage of 4k will load-down the 2k of the 1st stage so its gain will be reduced to 0.67. An input impedance for the 2nd stage of 10 times the RC value of the 1st stage...
  8. audioguru2

    BJT biasing formulas

    The voltage gain of a common-emitter transistor stage is RC/(Re+RE). If RE is bypassed or not present then the gain is RC/Re. The output will be very distorted without negative feedback provided by RE.
  9. audioguru2

    Audioguru FM Tx

    Try both. The 4.7k might be slightly better. You might not notice the difference, it will be very small. ;D
  10. audioguru2

    help me with this computation

    Hi Staigen, People who post fuzzy Jpeg schematics should be shot! >:( 1) The output of the 555 is missing a wire at the left side of the schematic connecting it to the "up and down" buttons. 2) Yes, the ladder is backwards. 3) Maybe the author had a spare 74193 and wanted to heat his home...
  11. audioguru2

    BJT biasing formulas

    Hi Staigen, I had a great time working as a nubee engineer for Philips, it was both good and not so good. I got to see and play with all their new stuff like their compact cassette recorder/player and LEDs. A friend in accounting wanted me to fix his electronic organ. I never saw one before but...
  12. audioguru2

    the voltage drop across an Inductor instead of a Res. for current adjust.

    Hi Shahriar, Current builds slowly in an inductor then discharges slowly, making a triangular waveform. Therefore if you use its resistance and reactance as a current detector, then an overload at the output will give a delayed response because the overload will draw a massive current supplied...
  13. audioguru2

    Tracks Shape in RF PCBs are like two comb!

    It looks like a cheap but very accurate low value capacitor. ;D
  14. audioguru2

    BJT biasing formulas

    Hi Staigen, I started with the BC108 in a metal case which has the same chip as a newer BC548. Then came the BC148 in a strange boxy plastic case and serrations in the pins to lock it to a pcb. Then came the BC548 in a TO-92 plastic case. I also used PNP BC178, BC158 and BC558 ones. The last...
  15. audioguru2

    3 way speaker system

    If your speakers and amps have true RMS specs then an amp with a power rating of 3 to 10 times the speaker's rating can be used since music or speech is never continuously at max power. The extra power is needed for the speakers to produce momentary peaks in the music or speech without having...
  16. audioguru2

    3 way speaker system

    Connecting filters in series results in a response that is very droopy, attenuating frequencies that you need that are far from the desired crossover frequency and even attenuating the crossover frequency too much. Butterworth and Linkwitz-Riley filters use a circuit with feedback to result in a...
  17. audioguru2

    BJT biasing formulas

    Sorry, Autir. I was distracted by trying to run away from Walid who might try to kiss me or somethin'. I was also distracted by thinking that maybe Walid is a pretty girl and about meeting her. ;D Since I haven't used a BC548C transistor for about 40 years, I didn't know they aren't made by...
  18. audioguru2

    problem Led

    We did that already. Since you have lots of voltage then a battery probably isn't being used, so the 0.43mA current in the 56k resistor or 24mA in the 1k resistor when the LED is off doesn't matter. The numbers are crunched by using Ohm's Law. 
  19. audioguru2

    BJT biasing formulas

    Thanks for translating the document, Alun. Hi Walid, I wish your schematic wasn't a negative pic. 1) Your R1 and R2 divider doesn't have enough current. R1 can't supply the base current without even having R2. Your error was caused because you selected a Thevenin parallel combination of R1 and...
  20. audioguru2

    Electronic Memory!

    Hi Alun, In his 1st post, Mukhalled said he had a "(pc cd-rom) CD-player". If it is actually a portable CD player needing 3V at about 50mA from a car battery to 3V converter, and he needs backup time, then maybe he should just connect the voltage adapter to something that is continuously powered...
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