TI-H: RCL - Radio Chat Link

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TI-H: RCL - Radio Chat Link

If you are interested in helping with the creation of a RCL - Radio Chat
Link!


Then read the following:


Here is what I think we should do:


The link should be for 2 calcs in one room only!!!!


The reason for this is:


1. The chat program must be limited in size, a 20 KB chat program simply
won't work, (No place for the games!!). An error correcting, peer to peer
network program would definately take up a looooot of space on the calc.


2. Since we would need it to be quiet (NO NOISE AT ALL) when we were
broadcasting. We would have to use FM (Frequency Modulation) for
transmitting, since that is virtually noiseless (When the signal is
powerfull enough).


3. The next problem is that an FM reciever ONLY picks up the strongest
signal. I.e. mixing 10 signals over the same frequency is impossible, as
only the most powerful signal would be recieved. Therefore the link would
require 10 transmitters and 10 recievers to work properly.


4. 10 Transmitters would broadcast virtually "everywhere", making detection
easy at an exam. (The reason for not using the earpiece and the walkie is
that it looks kind a strange on the table at the math exam. A calculator
looks a little more "normal")


We would in my opinion have to make the link to be used with ZShell, (Not
TI-OS)


The reason for that is that only 1 transmitter should be used. (No room in
the calc for 2 transmitters and 2 recievers, only room for 1 of each)


That one transmitter should have a switch so that it would be possible to
use 2 frequencies. If you only have 1 frequency, you wouldn't be able to
talk to transmitting calcs with your frequency.


The transmission distance could be anything from 1 meter to 300-400 meters.
And don't bullshit me. I've built my own bugs, the best one went as far as
1000 meters. But that was also an SMD (Surface mount) bug.


It would be cool if somebody would help with the following.


Creating the electronics.
Setting up a hompage for the RCL
Do the programming in ZShell
Testing the link


We could assign one or more persons to do each thing. 


PLEASE: If you don't know shit about electronics don't mail telling that
this is wrong, or asking for a network. I'm not capable of making that, and
not interested either! If you found a mistake and you do know what you are
talking about, feel free to tell it. Any relevant ideas or comments are
also appreciated.


If you care to work with me on this project. Then mail me:
						Laurits <CSN@dk-online.dk>




Methods for the transmitting and recieving:


The transmitter could be made with a crystal or a coil and capacitor.
I would prefer the crystal, as that is frequency stable.


We could use either the carrier or a tone for "HIGH" and "LOW" signals


No carrierwave = LOW
Carrierwave = HIGH


Tone = HIGH
No tone = LOW


If we use the tone we would need a multivibrator with a crystal to create a
low frequency (Maybe 20KHz). When the signal was recieved, a filter would
allow only this frequency to pass. The frequency could then turn a
transistor high or low.
This method would be very tolerant to incoming noise from the calc.


Try sitting with your calc next to a cheap radio, and mess with it. You'll
se what I mean. (If you have a CE calc. this probably won't affect the
radio)