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Help modifying a schematic

Discussion in 'General Electronics Discussion' started by Gurrier, Oct 16, 2011.

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  1. Gurrier

    Gurrier

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    0
    Oct 16, 2011
    I am planning to modify and build this circuit, it is essentially a Walkie-Talkie and therefore needs to transmit and receive audio. Unless I am mistaken this is achieved by switching all four of the arrows from r (receive) to t (transmit). I would like the circuit to be in normally receive mode and only change when a PTM is pressed. I have considered using relays and a variety of transistor circuits to do this but I would like this circuit to be relatively small therefore multiple DPDT relays is not ideal, is there any other way of doing this? Also I am a little confused about the inductor just below the antenna, I was going to make a ferrite core inductor unless anyone can direct me to a component I could buy with the correct number of coils.

    Thanks in advance.
     

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  2. davelectronic

    davelectronic

    1,087
    12
    Dec 13, 2010
    Hi Gurrier.
    Is this not what a transceiver does, stand by ( RX ) transmit ( TX ) your receiving on the unit by default until you push the PTT button / switch.

    Or do you want remote operation of the unit ?.
    Not sure where or if you can go smaller than a PTT switch, some relays are tiny.
    Or SMD components maybe.
    Dave. :)
    PS, Welcome to the forum. :)
     
  3. davenn

    davenn Moderator

    13,866
    1,958
    Sep 5, 2009
    The transmit and receive switching isnt a problem
    Yes it would normally be in receive and you push the switch to put it into transmit
    thats the usual way

    Have a look around the switches that will have a spring return built into them, they are available. with that you will achieve what you want just using 1 switch with multiple contacts :) no need for relays at this stage

    Element14 aka Farnell have toggle switched that are 3 pole 2 position with a momentary action ( the momentary is the spring return that I spoke of above)

    the model 5252B should be the one

    cheers
    Dave
     
    Last edited: Oct 16, 2011
  4. Gurrier

    Gurrier

    2
    0
    Oct 16, 2011
    Thank you very much for the replies and sorry this is late but I was away. Anyway I do not have the facilities for SMD and also I was hoping that I could use a single PTM switch for the call button rather then a toggle. However I was wondering whether I could use analogue switches for this as an alternative to relays but I have never used these before and am unsure of how they work.
     
  5. davelectronic

    davelectronic

    1,087
    12
    Dec 13, 2010
    Possibly a change over contacts switch, round button, non latching.
    Dave. :)
     
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