I think what you are trying to do is take the audio from one unit to feed the other so that one is the reciever and the other the transmit, what you need to do is open the rx unit and find the audio mute line that feeds a lite and take this signal to make a carrier activated switch. If you have no existing internal circuit or can't locate it you would then use an op-amp circuit to detect the voltage and current swing of the audio coming from the center of the volume adjustment potentiometer feeding this into a switching transistor for the transmit push-to-talk, this will also need to incorperate a timing circuit as well as in identifier for the station itself. That is a controller, not really a duplexor although it will allow the duplex function to perform - the duplexing of the rf is an altogether different game in itself, for this you will need a filter to block the transmitter output from desensing or destroying the reciever and if you look at these filters there is often an equal amount of filtering on the reciever as well. With walky talky power typically around 5 watts this can be done with 4 cavities instead of the 6 or 7 needed for higher power, for the 600kc ham vhf band split this each of these could be made from 3 3lb coffee cans soldered together with 1/4 wave folded dipole antenas inside, save one end and slide it in and out to tune for your frequency, use another end to keep the insects from getting inside - if you measure from the protruding element of one can to the next the connecting cable has to be an electrical 1/4 wave - the coax velocity factor will be used in the math equation to build this, 2 cans will be used for each rx and tx this allows one side to operate without affecting the other, if you can get this to work well you may be able to use just one antenna but you will probably have to use 2 until you tune each side independantly. The only place for a relay might be to control push-to-talk of the transmit radio based on the control line taken from the reciever radio, visit repeater-builder dot com for more detailed info, you will be able to see pictures of what you are trying to make.
focomirzet wrote: > > hi to everybody, > > i need some help with the following: > > I,m trying to build a home desktop repeater with two VHF hand held > radios. I've heard that some people posses schematics to build > duplexer switchboard between two radios mentioned above. That should > be electronic duplexer with relays or something similar to that, so > therefore i politely ask anybody who has either schematics or online > links related to this matter, to send me on this e-mail. > [EMAIL PROTECTED] > P.S > > THE reason for my quiery is that I'm living in country with weak > economy, so please understand that my resources are very limited and > this is the only way for me to obtain some useful info. > Do note that I have the knowledge and strong will needed to do the > task at all costs. > -- 73...Clark Beckman N8PZD Yahoo! Groups Links To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ To unsubscribe from this group, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
