Best stubbie external wifi antenna?

Discussion in 'Panasonic' started by stiffnecked, Mar 18, 2009.

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  1. Toughbook

    Toughbook Drop and Give Me 20!

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    I have done Mnem's hack on many of the old RIM antennas with STELLAR results. As good or better than the CF-29 type! All it takes is to unsolder few SMDs and then either use two SMD 000 resistors or, as I do, just solder a jumper where he shows in his post. BAM! Working wifi. Then I usually also mod in the passthrough so it is an easy install as it is all plug and play after the soldering is done. But it does mean that you have to take off the LCD top and the "4 screw" port cover on the bottom as well as removing the keyboard for access.

    I can't imagine anyone wanting a better signal than this setup gives.
     
  2. marconi

    marconi Notebook Consultant

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    I started out with mnem,s hack of course its very easy to do and will work tons better than the original config as your removing the harmonic filter that gets in the way at 2400mhz.
    It did work for me but what prompted me to go farther was the fact I was using the 1/2 watt card and wanted to see the antenna's return loss, and it was really bad, but it could have been just my luck.
    I found it worked but I didnt see much difference with the antenna extended or retracted , maybe 3db. I figured it must be going out the lcd instead or a mis-match, or bad/pinched cable. so thats why I did it a bit different, of course YMMV.
    My second attempt worked much better.
    What really worked the best was to add the rp-sma connector to the rear and use either an omni or a bi-quad antenna.
    I've even connected to a 10' dish that was up 660' up a tower out 30 miles from town and was able to connect to home, but had interference issues from others in town. talk about making netstumbler go crazy :)

    So basically, all I did was solder my connections much closer to the stem and ground , bypassing any residual inductance that added in from the board and 00 ohm resistors.

    Chuck
     
  3. marconi

    marconi Notebook Consultant

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    I should add that this works the best on the shorter RIM antenna's, the longer one's really need the reactance tuned out and even then they will have a very narrow vertical beamwidth. so they will have to be perfectly in the vertical position to use it when far-out from the access point.
    Up close it wont matter much, but the higher gain may become a health issue if using a high power card.

    Chuck
     
  4. mnementh

    mnementh Crusty Ol' TinkerDwagon

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    You see, this is what I WANTED to tinker with, but simply didn't have the proper equipment.

    Chuck, did you see my trial & error attempts posted here:

    http://forum.notebookreview.com/showthread.php?t=215522&page=2

    and the resultant "seat of my pants" results posted along with?

    I tried removing the poly PCB and soldering my antenna lead directly as you suggested - it decreased my reported signal level by more than 5dB at everything from 100' and out; that's why I went back to using a single 0 ohm SMD as a bridge.

    I suspect the differences we report are due to the differences in our basic setup; you started out with the CDMA antenna and I was using the analog Cellular antenna; plus I suspect you may have replaced the entire antenna cable back to the WiFi card. I did not; I re-used the existing semi-rigid cable and simply fabbed an adapter so I could retain the functionality of the RF dock connector at the back of my laptop. Of course, all this adds parasitic loss which changes the resonance of the circuit, which may have been why my setup works so well with an obviously mismatched antenna.

    Do you suppose that between the metal case and the cabling tomfoolery, I accidentally stumbled across a setup that's resonating at 5/8 wave or full-wave instead of half-wave? With the ground plane provided by the metal chassis, I can see it acting as a dipole instead of a monopole...

    mnem
    Dipoles? Monopoles? Sounds kinky...
     
  5. marconi

    marconi Notebook Consultant

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    Yes, I do believe that there is more to this as each time I've done this , its been a different result each time, of course some of this could be due to a slightly different length in the cable. This is microwave and any mis-match in the antenna will look different to the radio
    or analyzer with small changes in cable length , maybe you lucked out and yours is acting as a transformer for that and tuned out the reactance too.

    Yes, I did read your results and I commend you with that great job you did.,
    You did beat me to doing it., hehe. I did copy you the first time around, thanks.

    As we get away from the easy to match 1/4 wave it gets tough to try to tune these longer antenna's., without a matching network at the base of the antenna we are basically doing it with coax. kinda a poor way but sometimes it works great.
    I guess my next attempt, I will have to try to find the correct length and post it here.
    Hopefully using the factory cable. its 50ohm. but if its changed to a different diameter or manu it'l have different parasitic capacitance changing its length some.

    Hey, watch what your doing with that pole ..son
     
  6. mnementh

    mnementh Crusty Ol' TinkerDwagon

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    Yeah, I saw that you posted while I was posting my questions - LOL. Thanks for the props - I do believe that since you do this for a living, your WiFu is a bit stronger than mine. Also, since I was only messing with the 100mw & 400mw Atheros cards, I'm sure I get a bit more leniency in the reflected wave. I'd be curious to see what the actual numbers with my complete setup might look like; but I'll probably be ashamed. :eek:

    I really was surprised at Panasonic's take on the overall antenna design; there really is a HUGE mass of metal there given the frequencies we're operating at; lots of opportunity for parasitic loss. That slip ring is flippin' HUGE!

    mnem
    BoingyBoingyBoingy...
     
  7. stiffnecked

    stiffnecked Notebook Consultant

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    What is a bi-quad antenna? Do you have an example? Thx. Scott
     
  8. marconi

    marconi Notebook Consultant

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    Sure thing http://martybugs.net/wireless/biquad/

    As you can see if your handy with some simple tools and can find the connectors ok,
    You can build it pretty easy and you wont have to tune it.
    It has some pretty good gain for those hard to reach areas

    Chuck
     
  9. marconi

    marconi Notebook Consultant

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  10. stiffnecked

    stiffnecked Notebook Consultant

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    Thanks for the links. Just following some of the discussions on the links is interesting. I've got a few ideas now.
     
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