TI-H: Re: Re: radio link
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TI-H: Re: Re: radio link
someone else do the protocol... but any digital protocol plugged into the
mic jack of a commercial radio, say one of those nifty Motorola FRS jobs,
would give you a range of around 1/2 to 1 mile... and plus, each system
would be totally independent of frequency, so just say "channel sixteen" to
your friend and you have your own private link w/o interference... also,
most FRS radios have "quiet codes" to not activate the audio out unless the
code is received.
FRS (family radio service) radios are decent, FM, license-free, and cost
anywhere from $50 to $150. Cheap enough for my sorry ass, especially when
compared to the work of designing FM circuitry myself.
you want long range? get out your 10-meter ham radio, do it there -- the
circuitry'd be the same -- send grayscale pixellated naked images of
Christina Aguilera to your friends in Japan on 5 watts; the sunspots are
pretty good this year, so 10 meters should get around the ionosphere fairly
well.
It's gonna be slow, though. It's an analog-to-digital system, being put
through the voice filters in the FRS radio, so I'd guess that anything over
9600bps would not be possible. Some simple error correction would be
necessary, probably in a program on the TI.
The receive end should just be a Schmidt trigger to turn the analog signal
into a digital signal with a threshold; just then pass that to a decoding
driver on the TI.
what i wonder, is if you can get the TI to do the protocol work -- you can
send & receive raw bits on the link port, so just make IT do all the work.
'course, this system wouldn't have TI protocol compatibility -- since the TI
protocol is a mite funky, you'd need lots of extra circuitry to convert back
and forth, plus you might run into bandwidth problems. So, it's a question
of programming vs. hardware, and programming's free.
It's too bad you can't write a little nubbin for TI-OS to rewrite the
communications driver to change the protocol in software.
With minimal hardware, (minus the radio, of course) this thing would cost
all of five bucks to make (no microprocessor required, just a couple of
diodes and an op-amp), and the major drawback would be no ti-protocol
compatibility. whatever, just write a program to send files back & forth, &
include chat functions in it. a shell with IM-style ability would just about
make my day.
--nick
Nick Foster / Bistromath / zaphod@coe.neu.edu
KeyID 2048/1024 0x663CB446
6CAF FFD4 F9BA 64BA ECF9 032E 7402 3886 663C B446
----- Original Message -----
From: "Bryan Fields" <kb9mci@urbancom.net>
To: <ti-hardware@lists.ticalc.org>
Sent: Saturday, March 25, 2000 6:34 PM
Subject: TI-H: Re: radio link
>
>
>
> > Another feature that would be nice... a directional antena option. I
don't
> > like super long range stuff because it could interefere with others. If
> > there were a way to focus the low power guy to be able to go long range
in 1
> > direction, that would be awesome!
>
> I like the idea of directional antennas too, but what freq. this link
> will be on will limit the size of the antenna. the last link design i
> saw was on 433.920 Mc, even there a yagi with decent gain will be rather
> large to take with you. also if full duplex was needed the antenna would
> have to be brood band, from my experiences that is very hard to do with
> a common yagi.
>
> another thing to consider would be to use a simple antenna (i.e. a 1/4
> wave) and higher power. if this is on 443.92 it would be simple to
> raise the power up to 1-3 watts with a simple pa stage. i take it this
> would be a fm signal which would allow you to use a non linear amp,
> making it more efficient.
>
>
> as for cost $100 to $150 would be good for me.
>
>
> now for some questions.
>
> what freq. is this link on?
>
> what chips are you using for the transmitter and receiver?
>
> what is your website, if any?
>
> what power level will this put out?
>
>
>
> btw, i am not a digital guy, cant stand the 1's & 0's, so please keep
> that in mind if i stated something that is wrong in this case.
>
>
>
>
>
>
>
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> "If there be time to expose through discussion the falsehood and the
> fallacies, to avert the evil by processes of education, the remedy to be
> applied is more speech, not enforced silence."
> -- U.S. Supreme Court Justice Louis Brandeis, 1927
>
> "Necessity is the plea for every infringement of human freedom. It is
> the argument of tyrants; it is the creed of slaves."
> --William Pitt, 1783
>
>
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