A86: Re: Radio Link- Revisted and Problem Explained


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A86: Re: Radio Link- Revisted and Problem Explained



I went to my local Radio Shack (which is where you got your parts from, right?), and asked if they had any radio transciever components.  They said that they had the parts to build my own transceiver, but none pre-built, and then they tried to sell me a stupid two-way childs walkie-talkie....   So part numbers would be very helpful, or at least, the general frequency on which your transceivers opperate.
-----Original Message-----
From: HonorIam2@aol.com <HonorIam2@aol.com>
To: assembly-86@lists.ticalc.org <assembly-86@lists.ticalc.org>
Date: Friday, January 22, 1999 11:32 PM
Subject: A86: Radio Link- Revisted and Problem Explained


Please accept my apologies for my unresponsiveness to earlier mail message,
after all, I was going through finals week at my school.  When I first posted
my idea for a calculator radio link with 4 transcievers, I neglected to
mention my specific reason for using that many radio parts and not just as few
as possible.
The calculator uses a noninterruptable protocal for it's link transmissions.
What the sending unit will do is lower the power on one wire and wait for the
other end to lower the opposite wire, the recieving unit will interpret a 1 or
0 depending on which wire it was and upon lowering both wires, the sending
unit will raise the power of both wires.
Now what all of this has to do with radio links is this:  the signal has to
be continuous or the calcs will generate transmissions errors from timeouts on
the port.  If the signal is digitized through a modem, the lowering-raising
patterns will skip points and accidentally lower the wires when they need
constant voltage.  This is why we can't digitize the calc links with modems.
My calc radio link works perfectly fine for a range of about a 100 feet.  It
gets very little problems during calculator TI-OS transfers because the
raising-lowering patterns have great tolerance for interferences.  I'm
assuming ztetris has a linking routine similar to the TI-OS because it causes
few problems.  I have found that very few linking routines for the TI-86, TI85
and TI92 use continuous bitstream (where the recieving unit must keep up with
the transmitting unit or perish the connection) flow, but rather the raising
and lowering routines.
If somebody manages to comeup with a modem radio link that supports
continuous transmission like most analog communications, that would be great,
but I'm sticking with my 2 frequency version because it is simple and concise.
In response to earlier questions, I don't know the exact part # of the
transcievers,  I got the kind that have four prongs.  One prong was input, one
was output, and two were the negative and positive power leads.
The wiring of the power leads was more than obvious.  As for the other two
prongs, I first tried to wire them directly to the calc wires themselves, but
that caused the calc's LCD to go black (i.e. too much power!), so I grabbed
the extra 3.3K ohm resistors I had from my old calculator serial port link and
wired the output prong first to the resistor and then to the link.  I then
wired the input prong directly to the link.  I don't know how much more
powerful the flow from the transcievers was compared to the link, but the
resistor configuration happened to work perfectly.   I want to find some
transcievers that have the correct power output because I can't leave the link
on for more than about ten minutes before it gets really hot.  Oh well.
Tim Adkisson
<A HREF="mailto:honorIam2@aol.com">honorIam2@aol.com</A>