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  1. duke37

    Forum Upgraded!

    What does 'report' and 'like' mean? My eyes are getting on in years, I would like darker print and mybe little larger. The old forum let me run at 125% but this one disapproves. The system is much slower, I don't have broadband, the best it can be described as narrowband. It will take a...
  2. duke37

    Hall effect type sensor through 100mm of Wood

    Wood will have no effect on the magnetic field unless it is wet and the field is changing (eddy currents)
  3. duke37

    12 volt horn help

    There are several ways of doing this. One suggestion is to use a 555 to produce a pulse of the required length. Use this pulse to gently charge a capacitor and then use a LM3914 bargraph display to get up to ten sequencial outputs. Output 1 and 3 will need a couple of diodes to go to the same...
  4. duke37

    oscillator doesn't oscillator as I expect

    The reality is that it is not a LC circuit but that there are multiple circuits with coupling inductance and capacitance between every turn. If you measure the inductance at low frequencies, the capacitance effects will be negligible. If you measure at high frequencies, the capacitances may...
  5. duke37

    DIY High Voltage Function Generator Design

    How does 5000kg and a development cost of 50000$ grab you?
  6. duke37

    oscillator doesn't oscillator as I expect

    I do not think that the frequency affects the inductance greatly but it will affect the effective reactance. Short verticle aerials often have an inductance at the bottom to bring it to resonance. It is recommended that the coill is made with spaced turns to reduce the interwire capacitance...
  7. duke37

    oscillator doesn't oscillator as I expect

    Things are complicated, there is capacitance between turns so this will alter the distribution of current in the inductance. Also the effect of the capacitance will vary with frequency. I measure the inductance with an inductance meter and also measure the self resonant frequency with a grid...
  8. duke37

    Electronics Club

    I belong to two radio clubs, There is nothing that they do exactly. Everyone has their own interests such as. Chatting on the radio Building radios Putting on exhibition stations Instructing to get an amateur licence Swapping/selling components and equipment Contest operating 'Fox'...
  9. duke37

    oscillator doesn't oscillator as I expect

    Inductors are measured at low frequencies so that the effect of the inductor capacitance is minimised. At some highish frequency the inductor will be self resonant and above this, will behave as a capacitor. Hence the effective inductance will be less than the measured inductance.
  10. duke37

    New alternator to car cause relay to buzz - can you help?

    Be very careful about connecting anything to the alternator, if you connect to the main output, you are effectively connecting to the battery. Much heat and molten metal can result. I think the explanation of how the relay works is not correct. This was the case when a dynamo was the...
  11. duke37

    Need signal generator help.

    Even if the signal is not modulated, you can use it. Tune to a radio station, twiddle the generator around 450 to 500kHz and you will hear a whistle when the generator is close to the IF that the station is generating.
  12. duke37

    Need signal generator help.

    I am still here - just. Lining the box to screen it is not a bad thing but I think it not necessary at low radio frequencies. If the box is fully screened and the detection coil is inside, then nothing will happen. The little radio you have will be a superhet with an intermediate frequency...
  13. duke37

    New alternator to car cause relay to buzz - can you help?

    The alternator will have diodes in it which will allow charging but not discharging. The main output connection will be direct to the battery so could give a massive curent if you do not treat it right. The alternator seems to work OK at 14.3V so why worry? There is an auxilliary lead to...
  14. duke37

    Hi all, interference?

    What is a top charger? At 90A you are talking serious. Find out what device is causing the interference and fit inductors and capacitors to keep the rubbish inside a screened container. What problem is the interference causing?
  15. duke37

    Hi all, interference?

    Welcome to the forum. Shielded cables work well, shielded cable is used on microphones and bigger coaxial cables are used for radio frequencies. The cables will output what is input. A car will produce lots of interference from the generator, ignition and a multitude of DC motors. The only...
  16. duke37

    Help on dc motor small garage

    1. Use a microswitch which is activated when the garage is at its top limit. Use another microswitch to be activated when the garage is down. 2. Use a Hall effect device to sense the presence of a magnet which is fixed to the garage. I will have to think about a suitable circuit.
  17. duke37

    D-flipflop freq divider

    Does the 4013 have a power supply?
  18. duke37

    Electronic Earth Resistance Meter

    I think that earth resistance or soil resistance is done with the four probe method. A regulated current is passed between the outer probes and the voltage is measured between the two inner probes. A survey of resistance over an area can then be made to detect artifacts.
  19. duke37

    Blown resistor please help

    If it is a power input inductor, then it may have saved the rest of the circuit. Pehaps it could be replaced by a link. If it is an inductor in a buck or boost convertor then it will need to be replaced by the correct value. Dave is right !
  20. duke37

    Electronics Club

    As shrtmd said. I googled 'oklahoma city amateur radio' and found hamdepot.com with a list of over a dozen clubs. You could try looking on the ARRL website.
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