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2.4GHz absorption by plastics

Discussion in 'Electronic Design' started by martin griffith, Jul 16, 2007.

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  1. I've tried Mr Google, but I cant seem to find any tables about how bad
    plastics are at absorbing RF.

    For fun, I'm just about to make Jason Heckers' helix antenna
    http://www.wlan.org.uk/jhecker.html

    Any links?


    martin
     
  2. Tim Williams

    Tim Williams Guest

    Duh, put it in the microwave and see if it melts. ;-)

    Offhand, polypropylene Gladware containers are microwave rated.

    Tim
     
  3. Yeah I know the microwave trick, but I never intend buying one.

    thanks for the polypropylene pointer


    martin
     
  4. Check any reference book on electric materials. PVC is one of the most
    lossy. Polyethylene and teflon are the best. However it should not be
    very important for that antenna.

    Vladimir Vassilevsky

    DSP and Mixed Signal Design Consultant

    http://www.abvolt.com
     
  5. PeterD

    PeterD Guest

    Put your plastic in a microwave oven. Nuke it for about 20 seconds. Is
    it warm? Then it absorbs microwaves. If cool (it probably will be)
    then it doesn't.
     
  6. none of my neighbours have microwave ovens, neither do I :( or maybe
    :(


    martin
     
  7. Jim Yanik

    Jim Yanik Guest

    YOWZA..nothing like staying back in the Stone Age. ;-)
    I've had the same MW for almost 30 years.

    WHERE do you live?
     
  8. The munged email address <[email protected]___.es> seems to suggest
    Medina, Spain. Dunno.
     
  9. James Beck

    James Beck Guest

    Well, now is the time to buy one and write it off as an R&D expense :)
     
  10. Rich Grise

    Rich Grise Guest

    .
    Good grief! What planet do you live on? ;-)

    Cheers!
    Rich
     
  11. Rich Grise

    Rich Grise Guest

    These days you don't even have to buy one - you can find them in
    dumpsters, and they usually only need a fuse. (I've re-fused [no
    pun intended] ovens that then lasted another 5 years.)

    But I'd say if the original uses PVC, then PVC must be good enough. :)

    Good Luck!
    Rich
     
  12. Fred_Bartoli

    Fred_Bartoli Guest

  13. Jim Yanik

    Jim Yanik Guest

    they make some pretty small MW ovens these days.
    In my Indy apartment,I kept the MW on top of the refrigerator.
    And it's a full-size oven,not a sandwich-size model.
     
  14. LVMarc

    LVMarc Guest


    most plastics avsrob very little em energy, this is related to the
    dissaptaion factor for a given material.

    for a raidted wave, the relfection loss, obtsined from going from air to
    plastic, then plastic to air, gives a reflection loss .. this is an
    order of magnitude or greater thsn dissaption factor for ost plasics.
    the refletion losses are relate to eR the dilectric constant for the
    material.. if you want more loss...l add little rsitors on a wave space
    level to the material to increase losses. to decrease losses add....air
    :) good luck and Best Regards,

    Marc popek
     
  15. I see a 600W Sharp that can take a dinner plate and is only 13" wide
    (a 13" cube in fact):

    http://www.theapplecollection.com/iMac/iStore/HalfPintSplash.html


    Best regards,
    Spehro Pefhany
     
  16. Ah, Spanish kitchens, the bastard architects only put two accesable
    power sockets in as well. Phone lines and TV distro in each room, but
    not in the kitchen!

    I am a bit too old to change my cooking habits, ( a monster wok) and
    I'd rather put the money towards a new scope, and a new flint for the
    soldering iron


    martin
     
  17. Thanks, I think I spotted a VSWR meter circuit for 2.4G somewhere,
    might be worth investigating


    martin
     
  18. Rich Grise

    Rich Grise Guest

    So take a piece of the plastic you want to test to the microwave oven
    store and ask for a demo. ;-)

    (Or, just use the same PVC as the guy who wrote the page did.)

    Good Luck!
    Rich
     
  19. Ok. I'll quit moaning :)


    martin
     
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