External GPS antenna mount under GS beak

Discussion in 'Mapping & Navigation' started by MiGSel, Aug 6, 2004.

  1. MiGSel

    MiGSel GaStronaut

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    Under heavy tree cover and along rock walls I often get the "lost satellite reception" message with my Garmin SP2610.

    I wanted to know whether it makes sense to mount an external GPS antenna and whether it's bad to mount in under the GS beak instead of on top of something. As I didn't find a clear and straight answer anywhere, I did my own testing tonight.

    * [INT] internal antenna patch only
    * [ON] external antenna on top of the beak
    * [UNDER] ext. ant. under the beak
    * [TOP] ext. ant. on top box

    Put camera on tripod with interval setting: one pic every minute.

    Here are the results:

    [​IMG]

    1) The external antenna clearly gives me more satellites and stronger signals.

    2) On or under the beak doesn't seem to make much of a difference.

    3) On the top box seems weaker than under the beak.


    So in the garage I went and made me a bracket to fix the antenna under the beak. Looks like this:

    [​IMG] [​IMG]

    [​IMG]

    I'm happy with the result. :)

    I'll report back with satellite experience in the Black Forest, by the end of September.

    Cheers,
    Michel
    #1
  2. NJ_Bob

    NJ_Bob Occasional Adventurer

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    Michel, which external antenna are you using?
    #2
  3. zoolndr

    zoolndr the arched eyebrow

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    I, too, would be curious which antenna you're using. Looks like the <a href=http://www.gpscity.com/gps/brados/0270.4.7571879449873745279/ga26c.html"> GA26C REMOTE ANTENNA WITH BNC</a> ? You installed without the suction or magnetic mounting options, one assumes?

    Elegant use of zip ties, and congratulations on admirable application of scientific method to this vital question, though your report did lack reference to the requisite consumption of cold fermented sustenance as the required ritual celebration of triumphant engineering-tude. But much can be forgiven in light of your understandable excitement at achieving such significant results. :beer

    I'm curious if you tooled around the neighborhood at all while you were taking readings whether the signal strength of top-box vs under-beak would still have shown such a stark difference in reception.

    Were you mounting the GPS antenna unit on top of the top box, or underneath the topbox lid? Is that an OEM top box?

    [The endlessly deep black plastic might prove to have passive radio-jamming/shielding properties. Who knew? Perhaps all stock BMW luggage is manufactured from cast-off material from Northrop B-2 skin moldings? Might begin to explain how pricey those sidebags are...]

    Now of course you have-- innocently enough--taken the first step towards becoming the source for a new market demand in beak-brackets...vendor forum awaits. :wink:

    Z.
    #3
  4. MiGSel

    MiGSel GaStronaut

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    This is the antenna:

    10052-05 GA 27C low profile remote automobile antenna

    [​IMG]

    It wasn't mounted inside the topbox, just put on top of my Touratech Zega XL box. I wonder whether the funny result could be because of the flat aluminium surface under the antenna?

    Cheers,
    Michel
    #4
  5. Trevor S

    Trevor S Cap'n Flatulence !

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    As you would expect

    This bit has me confused, how the hell does it even work under the beak, there is no L.o.S ??? I put my GPS under the beak as a trial and got NO sat signals at all, as I would expect..... WTF ??????????

    That's odd but not knowing the exact metodology, did you do an "up and back" to take into account Sat location ? ie depending on where the Sats where in the sky, your body could have been bloking that bit of the sky where most Sats where when the ant. was on the top box behind you...

    I have always thought about just behind the windscreen, on top of the plastic bit in front of the instrument cluster, or another thought was a BT GPS there, talking to the PDA on my bars but then I have never really had a problem with just "on the bars" :dunno

    PS Try the ext. ant. on top of your helmet :D
    #5
  6. MiGSel

    MiGSel GaStronaut

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    Yes but with the 2610 it is worse than with my previous SPIII. So I hope it will be better with the external antenna added...


    None at all? Did you "put" it there or "hold" it there. Maybe your hand was covering the antenna patch?

    Yup, sat in a comfy chair next to the bike, so certainly lower than the top box, while the camera was doing its job.

    Maybe the moving clouds in the sky and the changing satellite position had something to do with it too, but it certainly didn't get better than under the beak. So that's where it's gonna stay for now.

    Cheers,
    Michel
    #6
  7. Trevor S

    Trevor S Cap'n Flatulence !

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    None at all and my hand was cradling the GPS, not over the antenae itself but I didn't expect there to be any signal, which is why I am totally suprised that you got any signal, put your hand over your aerial, that's esentially what your "beak" is doing.
    #7
  8. iswoolley

    iswoolley Restless traveller

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    I field tested an external aerial for my Garmin GPS V during a recent month-long trip on my Africa Twin. I mounted the aerial on the rear fender of my bike, under the plastic top box, and it worked fine. Good reception everywhere I would expect it, with only tunnels and really dense trees reducing the signal strength. Even when I had a large metal cable lock stored in the top box performance wasn't affected. My main concern was that the cable passed the engine with all those lovely spark plugs emitting EM interference, but I guess the cable is well enough shielded to not be affected.

    Iain
    #8
  9. Roamin

    Roamin Roamin Hands

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    I did similar experiments without the camera and the antenna now sits on top of my beak. I honestly did not try under....hmmm. I think I might move it just to prove to myself that it works under there. Wow...mabe I can buy more of sigels custom aluminum work! :rofl
    #9
  10. witzgall

    witzgall Goin' South

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    I was told recently that there are two things that can "Block" or degrade a GPS signal from reaching a receiver. Meat and Metal. Plastic, as long as it is reasonably thin, is not a big factor.
    #10
  11. TonyA

    TonyA beta tester

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    Anything conductive at microwave frequencies (meat and metal!) will block the signals. Even fresh water absorbs microwave energy and turns it into heat. That's how microwave ovens work.

    Nonconductors (aka dielectrics) can still cause GPS signal loss by detuning the antenna. But it takes a lot. The GS beak is pretty thin, much thinner than for example a non-metallized car windshield which causes no GPS problems.
    #11
  12. CroMag

    CroMag Gelande Sauté It

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    MiGSel, great job testing! Tony's right, plastic won't couple with the antenna like a conductor (aluminum) or water bearing meat. Hmmmm, there's a joke in there somewhere......

    Did the signal strength drop after the metal bracket was installed around the antenna?

    Dumb Question Department: when you guys did your testing, is only the external antenna pulling a signal or is the attached antenna working in parallel?
    #12
  13. Kaumajet

    Kaumajet H.I.D. Positive

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    :nod
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  14. Sam Buca

    Sam Buca a.k.a. Daniel

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    Great testing Migsel.

    I use the same external antenna for my 276C. I just stick it on the top of the
    tank with magnet and it stays. I completed a 2,500 mile trip to Ouray and back with no problems.

    The only benefit I see of having it below the beak is to keep the bike clean from attachments. I once saw an external antenna mounted on top of the beak and it looked quite cool.

    Why mount it below the beak?
    #14
  15. MiGSel

    MiGSel GaStronaut

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    I asked the same question before - not so dumb I thought - but never got a straight answer. Should try it myself by shielding the unit when the external antenna is on. If the signal doesn't weaken then...




    Why not if it works just as well. There's enough visible junk mounted on my GS already :rofl
    It looks cleaner, cable & antenna are more protected, nobody's gonna wanna steal it, no silly questions asked when I park the bike somewhere, ...
    #15
  16. Kritou

    Kritou n00b

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    As far as the Quest is concerned the unit looks for a given voltage to be present at the connector and only then disconnects the patch antenna - so plugging in a passive or the wrong model will not work
    #16
  17. TomW

    TomW Long timer

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    What's the antenna housing made of? Plastic, right?

    My only concern for an underbeak mount would be water and crud slung up from the wheel in the wet. I don't know how effective the front mudguard is at keeping stuff off the bottom of the beak. (Actually, as bizarre-looking as the beak is, I would like to think it's there for a reason, meaning the mudguard isn't that effective by itself.) The GA-26 antenna is probably advertised as waterproof or water resistant, but....

    The antenna probably wants to see metal underneath for use as a ground plane. Metal on the sides of the antenna may keep it from 'seeing' satellites low on the horizon. But, hey, if it works, go for it.
    #17