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  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Recent content by wookie

  1. W

    Paintball Radio project [need help!]

    27MHz is the CB band and you don't need a license. Is there something else that makes this circuit illegal apart from "appalling[ly] poor circuit[ry]" Below is my spec, copied from my specification powerpoint: this list is noticeably more concise than a normal spec, due to the fact it was for...
  2. W

    Paintball Radio project [need help!]

    Okay great, I can conduct some field testing and add it to my report- good idea :) What improvements could be made to the circuit to optimize it? Can't be all bad surely?
  3. W

    Paintball Radio project [need help!]

    Hi Nigel, I read the other thread (infact I revived it) but didnt see any claims that the circuit would be useless. 4 metres is a hell of a whip. I was hoping for much less than that. Yes I believe that the 22uH is a loading coil to make use of an electrically short whip. I used this calc...
  4. W

    Counting PCB Using Dual 7-Segment Display - Circuit Wizard

    Hi Ethan, I still use Circuit Wizard from my school days, its great at simulating circuits and playing around with components - you learn a lot. I would recommend a push-to-make switch that feeds into a decade counter's input. You will see on the software (use the Voltage Levels view) that...
  5. W

    Paintball Radio project [need help!]

    Hi everyone, I am working on a college project to design and build a 27MHz half-duplex walkie talkie for a paintballer and his teammates. The circuit I would like to use is the one below: I have some questions however: -Can I use a whip antenna, and how long should it be? -Can you...
  6. W

    Walkie talkie with LM386

    Hi Willen, Unfortunately I do not think it is that simple. The reciever (and possibly the transmitter) contains components specifically selected for 27MHz (the advertised frequency). I hope I am wrong about this, because I would like to make the circuit to function across the Citizens Band...
  7. W

    Walkie talkie with LM386

    Sorry to revive an ancient thread but I am looking to build this exact circuit. Found at the bottom of THIS PAGE, the writer offers the LM386 based solution as a variant of a discrete walkie talkie further up the page. I too have questions about the transformer - is it in fact a variable...
  8. W

    Frequency Modulating a Laser

    The delay over propagation distance is exactly what I am looking to determine, as it is the key to calculating distance traveled :) How I actually compute that is a whole other kettle of fish... We'll cross that bridge when we come to it :) Thank you steveB!
  9. W

    Printing PCB artwork to scale

    You can try to convert the image to a vector and then upscale without worry of distortions. There are various online tools that can convert black/white images to vectors for you, have a google and find which one suits your needs :)
  10. W

    Frequency Modulating a Laser

    Hi Steve, The plan is to measure the beat frequency of the light by comparing the outgoing sawtooth to the incoming sawtooth (reflected off the target). I have discovered that to do this, a sawtooth waveform is not ideal, as the rise/fall times are uneven. a perfect triangle wave is now the...
  11. W

    Frequency Modulating a Laser

    Okay, I think I understand. My chirp signal is not a true FM transmission, it is a hybrid of FM and AM, due to the nature of lasers in general - correct?
  12. W

    Frequency Modulating a Laser

    No info on that, the laser light frequency is fixed. Hmmm..... you can't change the frequency of the laser light, but can you use the frequency as a carrier for the "chirp" signal? more investigation needed
  13. W

    Frequency Modulating a Laser

    I HAVE MADE A MISTAKE. There is no "frequency modulation stage". I got confused with my own design. The laser driver is driven by the VCO output. The VCO is to operate linearly from 55MHz to 130MHz. Still learning here :)
  14. W

    Frequency Modulating a Laser

    Correct, I would need to find a diode without inbuilt current regulation, and design my own to drive it. I know this can be done, because there is a similar circuit here. Edit1: Also, I may be getting confused with FM terminology. I included the 433MHz carrier wave as I thought it would be...
  15. W

    Frequency Modulating a Laser

    Why do you say that? Just to give you an idea of my project, it goes like this: Clock -> Rampwave Gen -> VCO -> Freq. Modulator -> Laser The clock generates a 2kHz baseline for the system. The Rampwave gen makes a sawtooth waveform, making the VCO "chirp" between 4-60kHz. This chirp signal...

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