7.5khz and/or 10.8khz RF generator

Discussion in 'Wireless & RF Design' started by ~thrasher~, Oct 26, 2008.

  1. ~thrasher~

    Thread Starter New Member

    Oct 26, 2008
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    I am looking for schematics on how to make a small device that will emit a radio carrier frequency of 7.5khz or 10.8khz. I would like it to be powered by a 9v battery. Most of the schematics that I've seen are to high of a frequency and want some kind of input (they are for broadcasting a ipod or something to a radio). Any help would be great.

    Thanks,
    Thrasher
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    There is the small matter of legally emitting RF at a given frequency. And neither frequency you mention is on the broadcast band. For AM, that's 540 KHz to 1.7 MHz, and 88 to 108 MHz for FM.

    The carrier won't do much good without being modulated. That gets pretty complicated if you want to be able to retain the stereo channels.

    If legally low powered AM is enough, try the circuit at this link - http://www.techlib.com/electronics/amxmit.htm.
     
  3. ~thrasher~

    Thread Starter New Member

    Oct 26, 2008
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    What I'm looking to do is build a device that will activate an invisible fence collar (for dogs). Invisible fence uses radio carrier frequency 7.5khz and 10.8khz with a 30hz modulation frequency. The broadcast area would only have to be about 3 feet or so.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    For that distance, an oscillator signal fed into a wire might do. Then your problem is tuning to the receiver.
     
  5. ~thrasher~

    Thread Starter New Member

    Oct 26, 2008
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    thats just it. I'm going to need a pot (or something like that) on the transmitter because the receivers cant be modified. I have been unable to find a diagram of how to construct such a device.
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The frequecies you have given are in the audio spectrum.
    You could make an oscillator with an 4093 (7.5 or 10.8 kHz).
    This can be gated with another oscillator of 30 Hz.

    Greetings,
    Bertus
     
  7. ~thrasher~

    Thread Starter New Member

    Oct 26, 2008
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    So the first oscillator would be for the 7.5 or 10.8 and then put the 30hz oscillator on the gate input of the first? If thats the case what do you do with the remaining input? Is that the V+ input?

    Thanks for you help,
    Thrasher
     
  8. ~thrasher~

    Thread Starter New Member

    Oct 26, 2008
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    Also, what is done with the Iutput since i just want to generate the frequency? Is the output the antenna?
     
    Last edited: Nov 3, 2008
  9. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The remaining inputs can be put to V+.
    The output can go to the "antenna"( a piece of wire will probably be enough) .
    It will not have much power, but you say you only have to cross 3 feet.

    Greetings,
    Bertus
     
    Last edited: Nov 3, 2008
  10. ~thrasher~

    Thread Starter New Member

    Oct 26, 2008
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    Bertus,
    Thank you for all of the help. I have my circuits built. How would you recommend I check the frequency? I have chosen to put POT's in place on the R1's so i am able to fine tune the frequency. Was this a bad idea? Also, does the input voltage matter?

    Thank you again,
    Thrasher
     
    Last edited: Nov 10, 2008
  11. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The frequency can be measured with a frequency-counter.
    Some multimeters have the possibility to measure frequency also.

    Greetings,
    Bertus
     
  12. Audioguru

    New Member

    Dec 20, 2007
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    I Googled Invisible Fence.
    It is a wire buried around the "fenced-in area" that has a magnetic (not radio) signal of 7.5kHz. When the dog gets close to the wire then the receiver detects the magnetic field and zaps the dog.

    A smart dog would run very fast and leap over the burried wire. Then he might not get zapped.
     
  13. SgtWookie

    Expert

    Jul 17, 2007
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    Hold the dog collar in one hand. Start with the pot at the minimal resistance end.

    Tune the pot until you start getting zapped by the collar. Note the pot position. Continue tuning the pot higher until you stop getting zapped. Set the pot in between where you started getting zapped and where you stopped getting zapped. You will then have centered on the receiver's frequency.

    Then put the collar around your neck. :)
     
  14. ~thrasher~

    Thread Starter New Member

    Oct 26, 2008
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    Here is the text from invisiblefence.com:
    "We have never received a complaint indicating any of our products interfere or cause harm to pacemakers or their hosts. Our system works by radio carrier frequency -- either 7.5 kilohertz or 10.8 kilohertz. We utilize 30-hertz modulation frequency. As we are not privy to the electronic makeup of the device, we cannot give you a definitive answer. To be safe, we suggest you contact the pacemaker's manufacturer. The manufacturer knows their product intimately and is best suited to address your interference concerns."

    I took that was a radio signal since they said a "radio carrier frequency". Please correct me if I'm wrong. I don't want to make this thing and wonder why it wont activate the collar.

    SgtWookie,
    Thats what i was planning on doing, but it will be extra difficult (but do-able) since there are two oscillators that need to be set.

    Thanks to everyone for your help,
    Thrasher
     
  15. flat5

    Active Member

    Nov 13, 2008
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    Do you have access to a frequency counter or an oscilloscope? For the 30Hz you could use the scope easily. Sync the scope to 60Hz and see that there are exactly two cycles of 30Hz on the screen. Then bring the device to the receiver and adjust the 7 or 10 kHZ osc. for best results. or use a freq. counter. A calibrated audio osc. and scope might be used for the higher osc. Sync the scope on the audio osc. If you have a fantastic ear you might try to zero beat the audio osc. and your high osc. using a headphone but that freq. is very high for this approach. Hard to hear.
     
  16. joehill97

    New Member

    Jul 8, 2012
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    Hi everyone, I realize this post is several years old, however, I'm wanting to do the exact same thing as thrasher. I have 2 escape artists cleverly disguised as basset hounds, that have been tamed (thankfully) by the invisible fence. The problem is, the invisible fence collars do not respond to barking, only the perimeter wire. My neighbors text message me or call me when their bark collars (they wear 2 collars - 1 for barking, 1 for containment) seem to not be working - dead batteries or what not. I'd like to be able to "blast" a signal that would activate their shock collar. I want to find something that I can control via an X10 compatible appliance or power flash module so I can activate it via an X10 command. I just happen to be able to send x10 commands from my iPhone via Indigo Touch and a USB powerline interface, so I just need to create a blaster. I thought I found gold here in this thread and then it just falls apart at the end...has anyone successfully created such a blaster, or could possibly help me or point me in the right direction?
    Thanks for any advice - Joe.
     
    Last edited: Jul 8, 2012
  17. propane_tank

    New Member

    Jan 22, 2014
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    Same question here, actually. Any input?
     
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