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Spark gap transmitter

Discussion in 'Radio and Wireless' started by Rekin229, Sep 24, 2018.

  1. Rekin229

    Rekin229

    5
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    Sep 24, 2018
    I am new to electronics and recently I am trying to make a small spark gap transmitter, but I have no success. I have used the design I have attached as a file, but, as you can see, it has no labels for what type of capacitor, resistor, voltage input and number of coils it needs.

    I tried making it work for a couple of days but nothing works. I would really appreciate if anyone could tell me the specific parts needed (the type of resistor, capacitor etc.) or inform me if the whole circuit is not working.
     

    Attached Files:

  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Firstly, the battery probably needs to be several thousand volts.

    Secondly, once you get this working you are likely to get a knock on the door from your country's spectrum regulators. And they are not going to have smiles on their faces.
     
    hevans1944 and davenn like this.
  3. Rekin229

    Rekin229

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    Sep 24, 2018
    Yes, I know it is illegal. Correct me if I am wrong, but I thought if I was going to build a tiny antenna (about 50cm), the transmitter would would only ve able to travel a small distance, too smapl to cause any jamming
     
  4. davenn

    davenn Moderator

    13,112
    1,696
    Sep 5, 2009
    Sorry, but yes, you are wrong
    It doesn't work that way

    eg the small antenna out the top of my 1296MHz, 2.5 W radio can go 90km !


    PLEASE DO NOT consider putting a spark gap TX on the air
     
  5. Rekin229

    Rekin229

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    Sep 24, 2018
    Sure thing I won't when I know this know. My question is, what else could I do, instead of that? And something similar.
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    If you are really interested in building a transmitter, why not investigate getting an amateur radio licence?
     
    hevans1944 likes this.
  7. Rekin229

    Rekin229

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    Sep 24, 2018
    I did not knew that that exist and that you need it. Plus I just wanted to experiment just for an hour or so with it by making a short distance transmitter and receiver. That is all.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,131
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    Jan 21, 2010
    It will still be illegal with an amateur radio licence, however, if you are able to get a licence you will be better equipped to know what is legal and how to operate a transmitter.
     
  9. Rekin229

    Rekin229

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    Sep 24, 2018
    I mean if spark gap radio is illegal, I might do foxhole transmitter or something legal.
     
  10. kellys_eye

    kellys_eye

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    Jun 25, 2010
    There are many legal short-range wireless modules available as well as PMR devices (walkie-talkies) that are licence-free that could be used for the purposes you describe but they aren't straight forward in operation (relatively speaking).

    This is not a subject for the uninformed therefore we suggest you Google 'amateur radio' and look up the requirements for LEGAL transmission of radio signals. The rules are strict and the penalties for breaking them are quite severe.
     
    hevans1944 likes this.
  11. Audioguru

    Audioguru

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    Sep 24, 2016
    Does anybody still listen to the snap, crackle and pop of AM radio anymore? My FM radios do not produce the severe AM interference even in a lightning storm.

    Oh yeah, I forgot that airplane and control tower communications use AM so a pilot can "break in" and holler "MAYDAY, all engines have flamed out!":rolleyes:
     
  12. Ylli

    Ylli

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    Jun 19, 2018
    90% of my radio listening is AM. Nothing on FM interests me. If I want to just listen to music, I have a pretty good collection of MP3's.
     
  13. FuZZ1L0G1C

    FuZZ1L0G1C

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    Mar 25, 2014
    A spark-gap transmitter is essentially "white noise" being radiated into space, the earliest versions being used for CW morse-code telegraph-keyed modulation.
    For RF, this was usually tuned, or resonated to a transmitting antenna, for greater efficiency.
    Back in those days, interference with other stations or radio-frequencies was non-applicable, as the telegraph office / telecoms / post office was the sole source.
    Nowadays, however, RF bandwidths are narrower, closely packed, hence the strict control of 'willy-nilly' random transmitters.
    While on the spark-gap topic, an interesting experiment I tried out of curiosity:
    My 180W arc welder has an output no-load voltage of 48V AC, at 50Hz (mains frequency).
    As welding, especially gouging, at about 5mm distance, creates a plasma arc, I wondered if this would cause 'spark-gap' interference on my LW/SW/MW/FM world scanner radio (portable).
    Using the counter/timer on my mobile phone, I recorded the earphone output from radio to my PC's soundcard input as MP3.
    Each 'weld' or 'arc' test was done at fixed times, to differentiate from random RF noise.
    To my surprise, not the entire AM spectrum is affected, rather 'grouping' around areas such as 6MHz, 12MHz, etc.
    Longwave was swamped, and MW quite noisy, so maybe the lower 100-1600KHz frequencies are strongest.
    FM was not affected, except when tranny is very close to arc.
    At about 10-15m, the 'Arc' hum tapers off.
    ADD: The frequency spectrum is affected by the length of the arc, so can be considered a 'white noise' wideband radiated source.
     
    Last edited: Mar 7, 2019
  14. Ylli

    Ylli

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    24
    Jun 19, 2018
    No resonant circuits in that welder. All the noise is spread out over a wide spectrum (with local clusters as you stated). Add a resonant 'tank' and the noise generated will concentrate near a single frequency and thus be 'amplified' at that frequency.
     
  15. duke37

    duke37

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    694
    Jan 9, 2011
    Rekin229
    I assume you are in Shropshire. There are two radio clubs in the area. SalopARS does a foundation course for an amateur licence and TelfordARS meets at Harper Adams.
    To get sparks, use a car ignition coil with a driver circuit. Some people have used them to charge electric fences. The fencers can be quite dirty, I can tell if it is my brother phoning from the clicks.

    I see that the thread is quite old and has been resurrected for a change of subject.
     
    Last edited: Mar 7, 2019
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