digital radio transmitter schematics

need digital radio transmitter schematics that will work with microcontrollers.
THANKS

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easyarm wrote:

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.



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greeting,
http://dtusat.dtu.dk/group.php?c_gid=7&PHPSESSID Š15807b22370d1ff7c854a08ba 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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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
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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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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

scrambler
form,
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Hi Ken

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
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Hi Ken

No problem - if I had a penny for every time I had a minor aberration...
PSK's used quite a bit still.

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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wrote in message> > ** The project is sold as a series of kits by the author - programmed

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

** 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
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<< ** 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
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"Niels Damsgaard-Sψrensen" <
"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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wrote>>> There's allegedly one in the Nov Silicon Chip.

Is there a url ? Nothing obvious turned up with his rather uncommon name.
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with your order.
The UHF modules are by Laipac as sold by : www.commlinx.com.au
......... Phil
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wrote>>> need digital radio transmitter schematics

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.
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Only 1200bps sinngle duplex though 8-(
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