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Transceiver Circuit

Discussion in 'General Electronics Discussion' started by Ty Ban, Aug 27, 2017.

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  1. Ty Ban

    Ty Ban

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    Aug 27, 2017
    Ok I get it. Thanks
     
  2. Ty Ban

    Ty Ban

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    Aug 27, 2017
    ]
    What would the potentiometer do to the circuit during transmit mode?
     
    Last edited by a moderator: Sep 7, 2017
  3. Ty Ban

    Ty Ban

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    Aug 27, 2017
    Does the transmit part of this really connected to the other received part?
     

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  4. kellys_eye

    kellys_eye

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    That circled part of the schematic only changes the operation of Q1 from an 'accurate' crystal-controlled oscillator (during transmit) and a 'looser' oscillator used for the mixer circuit that Q1 operates as during receive.
     
  5. Ty Ban

    Ty Ban

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    Aug 27, 2017
    So it really is connected? The circled one
     
  6. kellys_eye

    kellys_eye

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    If the walkie-talkie is in 'receive' then ALL the switches will have the wiper (the arrow) connected to the points marked 'R'.

    Equally if the walkie-talkie button was pressed (transmit) then ALL the wipers (arrows) will be connected to the points marked 'T'.

    At no point are the wipers (arrows) ever NOT connected to anything. They are ALWAYS on either 'R' or 'T'.

    The schematic only shows them 'disconnected' because they don't presume to know what condition the circuitry is going to be in at any one time.
     
    davenn likes this.
  7. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    As a personal preference I would rather see the PTT switch shown in the RX position. A simple note "Switch shown in RX position" will suffice. Shown as is it can be interpreted as a center off switch.

    Chris
     
  8. kellys_eye

    kellys_eye

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    So would I.... but we can't really expect a professional schematic for such a cheap'n'cheerful device. It serves the purpose - to those that have the basic concepts of schematic reading...
     
  9. Ty Ban

    Ty Ban

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    Aug 27, 2017
    Thanks for all the help. Really appreciate it.
     
  10. Audioguru

    Audioguru

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    Sep 24, 2016
    The potentiometer adjusts the level of your voice when you transmit.
    The RF transistor is a crystal oscillator during transmit and is a super-regen circuit (not a mixer) during receive. A simple super-regen circuit is used as the radio receiver in children's radio controlled toys.
    The very simple transceiver is a child's toy.
     

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  11. Ty Ban

    Ty Ban

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    Aug 27, 2017
    Oh ok thanks for the info.
     
  12. Ty Ban

    Ty Ban

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    Aug 27, 2017
    So I made the actual PCB layout, solder the components and when I test the circuit, there was no noise coming out of the speaker, but I can hear the " snap sound " inside the speaker whenever I turn on the main switch meaning there is a voltage flowing. I cant transmit and receive in either the walkie talkie (cause I made 2). In the picture below, can you tell me where among the 12 pins of the push switch should I connect each T,R, COMMON(arrow)? cause I think there is where I made a mistake. Please help, thanks.
     

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  13. Audioguru

    Audioguru

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    Sep 24, 2016
    The switch is simple to see what connects to which of its pins.

    The RF transformer connects to the antenna and the transformer has a tuneable ferrite core.
    Does your RF transformer have a ferrite core?
    Have you tried to tune the transformer?

    Maybe you should buy a pair of cheap walkie talkies to see the parts they have.

    Here is the switch wiring:
     

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  14. Ty Ban

    Ty Ban

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    Aug 27, 2017
    Is the RF transformer your talking about is the inductor slug? (Cause you can tune it)
     

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  15. Ty Ban

    Ty Ban

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    Aug 27, 2017
    That is what my actual pcb is, the one with the circle is the inductor slug.
     

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