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McDeHack

GPS Antenna

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Has anyone got any info on GPS Antennas?

As an amatuer I like to build. (also too tight to buy) I would like to build an external antenna for my Garmin Streetpilot. I need dimentions Etc.

G6ITD

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I do not know about conecting them to the unit but,

I would think just a wire the right length would work.

 

That's "mister" radio to you.

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quote:
Originally posted by McDehack:

Has anyone got any info on GPS Antennas?

As an amatuer I like to build. (also too tight to buy) I would like to build an external antenna for my Garmin Streetpilot. I need dimentions Etc.

G6ITD


Hello,

The signals from the satelites are circularly polarised. That means, that you need a circularly polarised receiving antenna too otherwise you have a lost of 3dB. Furthermore the antenna should have a uniform radiation pattern, because the satellites can be every where in the sky. The antenna of the Garmin is circularly polarised and can receive from all directions. If you look in that antenna you find a thin wounded-up PCB with several quarter wave lenghth monopoles, coupled with a pair af have wave lenghth stubs. So it will be very difficult to make a working home-brew antenna. You can gain more profit in constructing a pre-amp with lower noise figure. But to get a low noise figure you need a lot of experience in constructing and measuring.

73's Jan PaoJGF

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Unless you are comfortable using surface mount devices, desinging stripline antennas for the 1.8Ghz band, and using sub-minature (SMB,SMA) connectors, I think your best option would be to go to a place like eBay, or do a search for GPS Antennas, via Google, and purchase an Antenna, I have bought several active antennas for about $20.00,

 

Captnace

W4ACE

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depending on what you want it to do. We were making circular yagi's years ago for 1.68 GHz, which is the output for the radiosondes on the National Weather Service WX balloons. Yes, we actually track and recover the balloons! And you think a terrestrial foxhunt is a challange...

 

I would start with some crossed dipoles 3/8 wave above a ground plane. (Turnstyle) Then experiment with the distance above the ground plane.

 

Of course, the two most popular are the patch, and the quadrifilar helix. The patch is a possibility. I have not had much luck with building the quad-helix. I am using a standard helix at 2.4 GHz for my AO-40 downlink, but I do not think a standard helix would be good for GPS.

 

Good luck.

 

Mike.

 

Mike. KD9KC.

El Paso, Texas.

 

Seventeen minutes after her FIRST call for help, police officers arrived to find Ronyale White dead.

 

Prohibiting self defense is the ultimate crime. Police carry guns to protect themselves. What protects YOU ???

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I made a patch antenna for my Garmin GPS 45 a few years back just for the fun of it, and it worked great until the magnet holding it to the roof of my car let loose. I didn't have to deal with the SMA connector since my GPS45 used BNC, and the line losses of RG-168 were so bad that I had to switch to RG-58 immediately.

 

A quick web search revealed plans for these two, the patch version is what I built:

 

Helical:

http://home.iae.nl/users/plundahl/antenne/helical.htm

 

Patch

http://home.iae.nl/users/plundahl/antenne/patchant.htm

 

Jerry.

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