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digital radio transmitter schematics

Discussion in 'Embedded' started by easyarm, Dec 6, 2003.

  1. easyarm

    easyarm Guest

    need digital radio transmitter schematics that will work with

    easyarm, Dec 6, 2003
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  2. easyarm

    Android Cat Guest

    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?)
    Android Cat, Dec 6, 2003
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  3. easyarm

    easyarm Guest



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

    is this a right choice ?

    easyarm, Dec 6, 2003
  4. easyarm

    Rod Speed Guest

    Rod Speed, Dec 6, 2003
  5. easyarm

    easyarm Guest

    easyarm, Dec 6, 2003
  6. easyarm

    Howard Long Guest

    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

    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

    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
    Howard Long, Dec 7, 2003
  7. easyarm

    easyarm Guest

    very informative.

    the oz radio modem is more like a kid's toy.
    easyarm, Dec 7, 2003
  8. easyarm

    Phil Allison Guest

    ** 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
    Phil Allison, Dec 7, 2003
  9. easyarm

    easyarm Guest

    is this one better?


    too many restricted, no way we can advance in research.
    easyarm, Dec 7, 2003
  10. easyarm

    Phil Allison Guest

    ** 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

    .......... Phil
    Phil Allison, Dec 7, 2003
  11. easyarm

    Rod Speed Guest

    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.
    Rod Speed, Dec 7, 2003
  12. easyarm

    Rod Speed Guest

    Is there a url ? Nothing obvious turned up with his rather uncommon name.
    Rod Speed, Dec 7, 2003
  13. easyarm

    Phil Allison Guest

    ** You can email: with your order.

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

    .......... Phil
    Phil Allison, Dec 7, 2003
  14. << ** 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 ;-)
    =?iso-8859-1?Q?Niels_Damsgaard-S=F8rensen?=, Dec 7, 2003
  15. easyarm

    Phil Allison Guest

    "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

    Seems like you are already doing that.

    .......... Phil
    Phil Allison, Dec 7, 2003
  16. easyarm

    Ken Taylor Guest

    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

    Ken Taylor, Dec 7, 2003
  17. Geoff McCaughan, Dec 7, 2003
  18. easyarm

    Howard Long Guest

    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
    Howard Long, Dec 7, 2003
  19. easyarm

    Luhan Monat Guest

    You dont need to do any fancy encoding to transmit digital data. Is
    this anything like what you are trying to do???

    Luhan Monat, Dec 7, 2003
  20. easyarm

    Ken Taylor Guest

    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??


    Ken Taylor, Dec 7, 2003
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