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Reducing the value of R5 on the Parallax TX RF Mod. part#27980, For more range/ — Parallax Forums

Reducing the value of R5 on the Parallax TX RF Mod. part#27980, For more range/

$WMc%$WMc% Posts: 1,884
edited 2009-08-26 03:45 in General Discussion
Hello All

I have reviewed the specs for the LINX TX chip, The chip should be·good for ~3000'~. I have noticed that Parallax has reduced the power/range of the LINX TX chip via R5, "a·600 ohm resister". The Parallax range spec for the LINX TX is now down to ~500'~.·Besides saving power, Why did Parallax limit the range of the TX Mod. part# 27980?

Has anyone tried to lower the value of R5? to increase the range?


___Thanks in Advance______________$WMc%_________

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Comments

  • HollyMinkowskiHollyMinkowski Posts: 1,398
    edited 2009-08-24 12:26
    If you try increasing the output power by changing the resistor do it a little at a time.
    Don't just go for max out. I modded a LINKSYS router to have max output power
    and overheated the output stage :-(

    Ended up shelling out 47.00 for a new router.

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    - Some mornings I wake up cranky.....but usually I just let him sleep in -
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2009-08-24 15:23
    Hello,

    Unfortunately opening up a transmitter for full power output borders on potentially violating some FCC rules. The engineer who designed the board had to do some research and IIRC typically sub-systems of the category of the RF transceiver do not need to be FCC certified. However, there are still guidelines for power output for AM and FM devices. I believe the range exceeds our expectations given the power reduction necessary to stay within these guidelines though. Potentially you could modify the resistor value which may or may not render the device not to comply with FCC regulations. In any event Parallax Inc. can not be held liable for such a modification. Take care.

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    Chris Savage
    Parallax Engineering
  • $WMc%$WMc% Posts: 1,884
    edited 2009-08-25 00:56
    Thanks for the info

    Mr. Savage: I liked your feed back and it was what I expected. Thanks

    HollyMinkowski:· I see Your point. This is why I wanted to reduce the value of R5 and not eliminate it!
    ······················ ..........Thanks for all of the RF info in My other post................


    ___Thanks_for_the_Replys_______$WMc%_____

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    The Truth is out there············································ BoogerWoods, FL. USA

    Post Edited ($WMc%) : 8/25/2009 1:02:33 AM GMT
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2009-08-25 15:41
    As a side note, after seeing stuff like the article below,·we have to consider how reckless we are with spamming the airwaves with RF transmissions. =)

    http://tech.yahoo.com/blogs/null/147548

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    Chris Savage
    Parallax Engineering
  • $WMc%$WMc% Posts: 1,884
    edited 2009-08-26 03:45
    Chris Savage

    I am very secluded from the rest of the world. My nearest neighbor is about 1 mile away(5280')~...I plan to reduce R5 just low enough to have a good signal at the very back 40ty of my property.

    I'm an old school HAM operator, I'll be compliant, I just hope everyone else will be as well.


    __________$WMc%____________

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    The Truth is out there············································ BoogerWoods, FL. USA
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