Tuesday, January 17, 2006

Homebrew GPS re-radiating antenna for portable units

Dear All,

Mini Power Supply homebrew for GPS receiver and Interface connector wiring for Garmin Etrax Legend.

Amateur Radio and Automatic Positioning Radio System (APRS) Setup

Portable Re-Radiating Antenna set (MCX) - package - Consists of GARTX + GAST3X Code:GART3X - $47.90 sold in Hong Kong.

Homebrew GPS re-radiating antenna for portable units!

I bought a Garmin Etrax Legend GPS hand held receiver last week from Singapore and was not too happy with the performance since it was not able to received the traking satellites properly since I placed the unit on my car dash board.

My next step is to homebrew an Active Re-Radiating Antenna for my hand held GPS receiver! By combining a homebrew PCB board GPS antenna at 1.5GHz with a simple Pre-Amp circuit and a induction loop coil placed just above the GPS receiving antenna will enable better reception of the GPS satellite.

Have anyone try this experiment before? Or anyone have used a commercial version and does it claimed to work? Any feedback is much appreciated!

I also learned how to upload free Malaysia Maps into my GPS receiver learn FREE from "GPS Maps of Malaysia & Singapore" and FREE World Maps for GPS and FREE tips on Uploading Maps into Garmin GPS unit



Rodney Yeo

P.S. -> Thanks to Tony Yap 9W2YAP, Mat 9W2TTT and others for the ideas and insperation!


  • Hi Rodny,

    Congratulation to you for getting a new GPS receiver. Anyway, I'm also new to GPSR. And i owned a GPSMAP 76. Currently I'm looking for a MCX external antenna because my GPSr cannot detect any "bird" up to the sky if I'm inside my car. This is because of my car were tinted. Hope to make one homebrew GPS antenna myself but my knowledge on it is 0%. haha. Anyway, hope you'll success in this homebrew project. Do inform me when you are done with this re-rad antenna. Good luck


    By Anonymous Anonymous, at 4:03 PM  

  • Dear Simon,

    Many thanks to you for your interest in experimenting on the Re-radiating antennas for GPS.

    I heard many other users advice us to use this device for especially portable GPS units like ours which does not perform well in cars especially with V-Cool!

    I am trying to find more info to develope a more simpler design so that any other member can make it or buy it for a small cost fee to be used with their portable GPS units.

    I will definately post the prototype design with actual live test performance benchmark to see how good is this homebrew design.

    We also have another ham member 9W2TTT who are also interested to test it with his BlueTooth GPS portable unit. But his has a small hole to plug in the external antenna.

    But my does not have the small antenna hole to attach it directly. Therefore I have to use this re-radiating technique.

    Till then keep me informed if you have any useful information to aid in the development and design of this design.




    By Blogger Rodney Yeo @, at 9:57 PM  

  • Dear Simon,

    I think this is a simple design we can construct. I



    By Blogger Rodney Yeo @, at 11:30 PM  

  • Hi Rodney,

    Yes, the two link you gave is very useful and look like very easy to build. But that's just power/transmitting unit. It still can't work without an external antennna. As i know the antenna itself is hard to build.

    And many of the forumer at advise me to buy at
    or get one at SG.

    Currently i'm still looking for someone who want to sell their antenna / someone who want to buy from the website above ( so that i can 'tumpang' them buy one more unit for me) haha..



    By Anonymous Anonymous, at 4:46 PM  

  • Dear Simon,

    Yes you are right... but usually for receiving antenna, the precise dimension to the resonating RX frequency at about 1.5GHz is not critical... e.g. Base on S.W. Radio reception the longer the antenna the better it RX!

    So I am not too sure this same theory will most probably fits our purporse of application on our GPS RX application.

    I wonder can anyone with experience in GPS receiver usage please share your ideas and comment on this topic?




    By Blogger Rodney Yeo @, at 10:16 PM  

  • Rodney, I hope with the help from the 'bird' in the skies u can locate Ali.B. :) -- 9w2izw

    By Anonymous Anonymous, at 12:12 PM  

  • Dear Izwan,

    Hee hee! Thanks for the tips... I just got Mr. Alan Tan 9W2XYZ to help me, naviagte my way to Ali Baba.

    Here are the coordinates he gave me... 3d08m21s N, 101d37m50s E.

    Also note the key abbreviations d=degrees, m=minutes, s=seconds, N=North, E=East.... I think it's right!

    Thanks to Alan Tan 9W2XYZ again for his help on the GPS coordinates to Ali.B. via S.M.S.

    See you guys there on the special Friday as I will be bringing a new friend to the ham society soon!


    Happy Hamming!



    By Blogger Rodney Yeo @, at 8:56 PM  

  • great try rodney!

    By Anonymous Anonymous, at 10:24 PM  

  • great try rodney!

    By Anonymous Anonymous, at 10:25 PM  

  • I just ordered my GPS accessories online and here are the details...

    Code:GART3X $47.90 USD
    Portable Re-Radiating Antenna set (MCX) package consists of GARTX GAST3X
    Code:GEC01 $5.90 USD
    Connector for Garmin E-type 4-pin (spring pins)
    EMS10 EMS delivery to Asia/AUS $15.00 USD
    Grand Total = $68.80 USD payed via Credit Card using CCNOW.

    I will be receiving my GPS Accessories by Friday! More experiments after that using Tiny Trax for APRS projects!

    By Blogger Rodney Yeo @, at 11:20 PM  

Post a Comment

<< Home