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About Parallax 433 MHz RF Transceiver. Increasing RF range !!. Please, help. — Parallax Forums

About Parallax 433 MHz RF Transceiver. Increasing RF range !!. Please, help.

markustermarkuster Posts: 184
edited 2013-05-20 07:58 in Accessories
Hi,

I need to increase the RF range of the item 433 MHz RF Transceiver from Parallax.
( Please see attached)

I understand that I need just to replace one of these little resistors by a little
wire.

But my problem is that I don't know which resistor must be replaced.

Please help.

Thanks,
27982-L.jpg
700 x 700 - 79K

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2013-05-06 09:14
    We, of course, cannot condone modifying the 433 MHz Transceiver, nor can we support changes to it, however to answer your question the LADJ resistor (R2), which is 750 ohms by default, is indicated on your diagram by the letter I. I hope this helps.
  • markustermarkuster Posts: 184
    edited 2013-05-07 10:57
    Thanks,

    No problem , The RF will be inside a metal case , for this reason I need to increase range. Do you have the squematics ?
    Thanks, again.
  • SRLMSRLM Posts: 5,045
    edited 2013-05-07 14:20
    markuster wrote: »
    Thanks,

    No problem , The RF will be inside a metal case , for this reason I need to increase range. Do you have the squematics ?
    Thanks, again.

    Providing schematics with the change would be supporting the modification. These modules have been certified by the FCC in their current form, and if you make modifications you may be running an illegal transmitter. Even if it is in a metal case.
  • markustermarkuster Posts: 184
    edited 2013-05-07 15:08
    Sorry,

    I Don't need schematics with the changes. I just need the original schematics , because I don't have
    any schematics. I tried to download from the Parallax website but I can't find the newest schematics .

    Please help.
    Thanks.
  • ElectricAyeElectricAye Posts: 4,561
    edited 2013-05-07 15:08
    SRLM wrote: »
    Providing schematics with the change would be supporting the modification. These modules have been certified by the FCC in their current form, and if you make modifications you may be running an illegal transmitter. Even if it is in a metal case.

    Mr. Savage does not mean to be a brute about this, it's just that SRLM is right: before a company can sell a transmitter, they need to get the device FCC certified in its present form. Mr. Savage is not even allowed to tell you how to make modifications, because that might be construed as offering a kit which has not been certified and probably couldn't get certification. Anyone telling you how to modify it, might also be in violation of the law - and you'd be astonished at how persnickety the FCC can be about people using too much power on the wrong wavelengths without the right licenses, etc.
  • markustermarkuster Posts: 184
    edited 2013-05-07 15:43
    Ok, I understand.

    My english is not good. I don't know if I am explaining my self.
    I will try to ask again but using other words:

    I would like to know if there is schematics in order to understand how can I modified the circuit.
    I tried to use the transeiver inside a metal box and the range was about 6 feet only.
    I don't need a mile range , I just need about 50 feet range. Even with 30 feet range I will be happy.

    Don't worry , I will not broke any kind of FCC law. I will just set the resistor to 50 feet range as a maximum
    range.

    But I need the schematics in order to tried to understand the product becasue I want to know if I can reduce the comsuption
    too.

    Thanks again,
  • SRLMSRLM Posts: 5,045
    edited 2013-05-07 16:11
    markuster wrote: »
    Don't worry , I will not broke any kind of FCC law. I will just set the resistor to 50 feet range as a maximum
    range.

    But I need the schematics in order to tried to understand the product becasue I want to know if I can reduce the comsuption
    too.

    Well, I can't help you find a schematic. My recommendation would be to follow the traces, and reverse engineer the schematic yourself. That, combined with the datasheets for the various chips, is probably all you need.

    But be aware that the FCC requirements are based on transmission strength, not "range". I don't know if the power is measured outside the device or not, but any modifications will likely require re-certification.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2013-05-07 16:35
    I'm not sure why the schematics aren't on the website. I will attach them here for now.
    pdf
    pdf
    433 MHz RF Transceiver_A Schematic.pdf
    127K
  • Duane DegnDuane Degn Posts: 10,588
    edited 2013-05-07 16:57
    ElectricAye wrote: »
    Anyone telling you how to modify it, might also be in violation of the law - and you'd be astonished at how persnickety the FCC can be about people using too much power on the wrong wavelengths without the right licenses, etc.

    I doubt (and hope) this isn't true.

    To increase the power of the device you'd want to reduce the resistance of R2. Using a piece of wire instead of a resistor will set the module to its maximum power.

    Now I just set back and wait to be carted off to jail.

    As others have mentioned, you can get in trouble with the FCC if your device outputs too strong of a signal. I do agree with the FCC rules and think you should abide by them. I just really dislike the notion that some information should be illegal to share.

    I feel confident passing along information available in the Lynx datasheet wont get be sent to jail.
  • ElectricAyeElectricAye Posts: 4,561
    edited 2013-05-07 17:11
    Duane Degn wrote: »
    I doubt (and hope) this isn't true......

    Yeah, you're right. No jail. Nothing like that. You'll just have creepy old guys like this one hanging around outside your house at night:
  • markustermarkuster Posts: 184
    edited 2013-05-07 18:09
    No problem , I will be very carefull with the power. Any way I think that replace the resistor to have 50 feet range is not a high power.

    Thanks for helping
  • MoskogMoskog Posts: 554
    edited 2013-05-20 07:58
    Another way to increase the range of the tranceiver is to replace the dummy load on top with a better antenna. The simplest way is to replace it with a piece of wire that is cut to quart of the wavelenght of the actual frequency. At 433MHz that should be something like 69.2cm /4 = 17.3 cm.
    A piece of a solid copper wire should work fine.
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