digital radio transmitter schematics

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need digital radio transmitter schematics that will work with
microcontrollers.


THANKS



Re: digital radio transmitter schematics
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More information would be good.

What data rate?  Short range or long range?  Point-to-point, digipeated,
or what?  One-way or two-way?  Full duplex or half?  What frequency and
what power level?  Licencing?  Cost per unit?  Parts or off-the-shelf?

In short, what's the application?  (And would a handful of R/C modules
make you happy?)

--
Ron Sharp.



Re: digital radio transmitter schematics

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greeting,

http://dtusat.dtu.dk/group.php?c_gid=7&PHPSESSID=8a15807b22370d1ff7c854a08ba
71d19

I would to built radio transceiver so that everyone can do the remote
sensing.

is this a right choice ?

http://www.amsat.org/amsat/articles/kd2bd/9k6modem/9k6modem.html




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Re: digital radio transmitter schematics

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That describes (amoungst other things) the 9600 scrambler technique in an
attempt to remove the DC component when modulating an FM transmitter and
then decoding it back using an FM receiver. It uses a maximum length
feedback shift register to randomise and then unrandomise the bits. You
never need more bits than the length of the shift register to resync. This
bi-state technology is quite old now, and I know that it has been
implemented in a PIC. I have two of the original designs made out of CMOS
4000 series logic, and I still use them today for satellite comms with some
of the older satellites still in operation. It has also been used for
terrestrial comms, but 9600 is so slow these days!

More recently, this 9600 modem has been implemented using DSP techniques and
PC sound cards.

Latterly, the use of phase and amplitude modulation has been implemented in
an attempt to get more bandwidth out of a high signal to noise channels such
as telephone modems. This is how you get 33.6kbps out of a 3kHz bandwidth
phone line.

For satellites, generating anything more than four states becomes
inefficient due to the need to use linear amplifiers which are inherently
less power efficient than their non linear class C counterparts. Four states
may be implemented by flipping between four phase states (-45, +45, -135
+135 degrees) by only changing phase, not amplitude. This is called offset
QPSK.

Anyway, that doesn't help what you are trying to achieve. The 9600 scrambler
technique is proven and does work quite well over radio, but you need to
consider some means of error detection and correction. In its simplest form,
this would be a retransmission, although these days there's all sorts of
techniques.

For the RF side...

If you are in Europe there is a project on an RS-232 radio transceiver in
the December 2003 Elektor.

I have used the RF Solutions devices with a lot of success
(http://www.rfsolutions.co.uk ) in particular the ones based on the
Radiometrix devices (http://www.radiometrix.co.uk ).

One thing to note - if you need full duplex things become a bit more
complicated. It's normally more cost effective to simulate it in software,
but for some realtime applications it's not possible and you will have to
operate on two different frequencies, probably in different bands to avoid
in-band desense.

Regards, Howard



Re: digital radio transmitter schematics

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some
and
in
such
states
scrambler
form,

very informative.



the oz radio modem is more like  a kid's toy.

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Re: digital radio transmitter schematics
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some
and
in
such
states
Hmm, I don't think I agree with this. In satellite work bandwidth is at a
higher premium than power (usually) so if you can conserve bandwidth by
using 8 or 16-QAM then so much the better. These, along with better coding
techniques, are becoming the norm now. However that's just detail - nice
post.

Ken


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scrambler
form,



Re: digital radio transmitter schematics
Hi Ken

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On the uplink this is a non-issue - we've got the advantage of plenty of
power down here on Earth.

For the tiny LEO birds I deal with generally a class C PA is used for
digital comms, but sadly I am talking about power budgets of a few watts.

I don't have any technical experience of dealing with many other digital
satellite systems, certainly none using QAM, although I had always assumed,
perhaps incorrectly, that anything other than class C was inefficient. As an
example, I was of the impression that almost all DBS TV is done using QPSK,
although as I only have a peripheral interest in this (as a user!), I am
referring to a single six year old text ("Issues in Advanced Television
Technology", S Merrill Weiss, Focal Press).

Of course, as you suggest if the application has limited spectrum and
sufficient power, then there is nothing wrong in using QAM. I just wish that
the satellites I use had that luxury!

I wonder which applications of satellites lend themselves to using QAM on
their downlinks?

Kind Regards, Howard



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a
coding
assumed,
an
QPSK,
that
Hi Howard.

Not sure what's up with my brain lately - that should indeed have been
"PSK", not "QAM". Sorry.

You're certainly right about efficiency with the class-C and all that - I
hadn't thought of the microsatellite application. I deal with bigger birds
but with the general limitation of restricted bandwidth. Horses for courses,
which I think we can safely assume we both knew but didn't think of
off-hand.  :-)

I see you're (probably) in UK - are you at Surrey? Are you actually working
in uSatellites??

Cheers.

Ken



Re: digital radio transmitter schematics
Hi Ken
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No problem - if I had a penny for every time I had a minor aberration...

PSK's used quite a bit still.

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courses,
working

You're getting very warm! I have more than a passing interest in the SSTL
satellites amoung others. I have a few meetings a year over there at
Guildford with some of the folks there including the infamous Martin
Sweeting, arguably the father of the microsat, a couple in Europe regarding
the International Space Station plus two in the US too, which keeps me out
of trouble. Most of my technical interest lies in the grounstation hardware
rather than the satellite itself, although I do run the European command
station for two LEO satellites.

Kind Regards, Howard
http://www.g6lvb.com might give the game away!



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There's allegedly one in the Nov Silicon Chip.
http://www.siliconchip.com.au/html/conts-nov-03.htm



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I am at least 13 hours of flight from you. no way to get that magazine.

can u post it up? please.
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**  The project is sold as a series of kits by the author  -   programmed
PICs are involved.

      Is  433.92  MHz  clear and legal for such use where you are ??





...........     Phil



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is this one better?

http://www.radiometrix.co.uk/products/spm2.htm


too many restricted, no way we can advance in research.



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programmed


   **  You asked for a schematic  ??????????

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**  I make it a policy never to help those who want to do something that is
crazy, dangerous or illegal.

      If they refuse to say what the application is then I assume it is all
three.





.........    Phil






Re: digital radio transmitter schematics
<< **  I make it a policy never to help those who want to <<do something =
that is  crazy, dangerous or illegal.

I do understand "dangerous or illegal" - but why "crazy"?
Edison did crazy things!!! Einstein too.
Crazyness is what made us climb down the trees.
Crazyness is beautifull ;-)
Niels

Re: digital radio transmitter schematics

"Niels Damsgaard-Sørensen" <


"Phil Allison" <

 **  I make it a policy never to help those who want to <<do something that
is  crazy, dangerous or illegal.


I do understand "dangerous or illegal" - but why "crazy"?


  ** Cos it just won't work and it wastes everyone's time.



Edison did crazy things!!! Einstein too.
razyness is what made us climb down the trees.
Crazyness is beautifull ;-)



  **  Then you go waste YOUR life and precious brief time here on planet
earth.

       Seems like you are already doing that.




.........   Phil






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Is there a url ?  Nothing obvious turned up with his rather uncommon name.



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  **   You can email:   snipped-for-privacy@u030.aone.net.au    with your order.

        The UHF modules are by Laipac as sold by :    www.commlinx.com.au



.........    Phil




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Dont have it myself.

Someone mentioned it in here, the local papershop
had sent theirs back the day I rang, literally.

Havent gotten around to doing anything about it myself.



Re: digital radio transmitter schematics


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Only 1200bps sinngle duplex though 8-(


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