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How can I optimize a homemade 1900 mhz outdoor dipole antenn


Place to discuss electrical design, tweaks, etc

Newbie

Posts: 1

Joined: Mon May 26, 2008 7:29 am

Post Tue May 27, 2008 9:06 am

How can I optimize a homemade 1900 mhz outdoor dipole antenn

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I have an Axesstel MV430i Gateway wich uses two indoor antennas. I was looking for a spot in wich I was able to get the best signal stenght posible inside the house so I placed it near a window and got -88 dBm signal strenght reading from one antenna and -81 dBm signal strenght reading from the other. I was not happy with that so I placed the modem outside the house to do a test and got -80 dBm signal strenght reading from one antenna and -78 dBm signal strenght reading from the other. I was happy with the signal strenght increase but, it is a problem to have the modem outside the house because of the weather and thieves so I decided to get a pair of outdoor antennas to be able to keep the modem inside the house. I searched the net and found the "Build your own Spy antenna" tutorial in this site.

I'm trying apply it to my modem so I made these two antennas with monofilament electrical copper wire (1/16 inches thick), 1/2 inches thick PVC plastic tube and RG6U coaxial cable for testing. I did the following to make the antennas:

Cutting process:

1) Cutted four 1.5 inches long pieces of copper wire to make the poles
2) Cutted two 5 feet long pieces of plastic tube to make the masts
3) Cutted two 1 inch pieces of plastic tube to atach the poles
4) Cutted two 10 feet long pieces of coaxial cable

Assembly process:

1) Drilled two 1/16 inch holes at about 1/4 inch of the edge of the two plastic tube pieces
2) Inserted each of the poles in the holes
3) Stripped about 1/2 inch at both ends of the coaxial cables
4) Drilled a 1/4 inch hole about 1 feet of the edge of the masts to be able to pull out the cables trought them and save cable
5) Inserted the cables trough the holes, masts, plastic elbows and the plastic pieces
6) Soldered one end of the coaxial cables to the poles and atached the TNC connectors to the other
7) Placed two plastic caps at the end of the plastic tube pieces to avoid that the water comes inside the antennas and pushed all the pieces together
8) Installed and tested the antennas

After the installation of the antennas I had the following signal stenght readings: -84 dBm from one antenna and -81 dBm from the other. As you can see I was not able to improve or keep the values obtained when I placed the modem outside the house as I was hoping, in fact now I have worse readings than the ones obtained when placing the modem outside the house.

So I'm looking for tips on how to optimize the performance of the antennas. I have the following questions in order to achieve that:

1) As you can see I placed the dipoles vertically. Wich is the best way to place them, vertically or horizontally?
2) About 1/8 of an inch of the poles are inside the masts. Do I need to have them all outside or is the lenght of the poles by itself the reason to obtain better reception?
3) Is there a better cheap material than copper wire that will help increase reception?
4) Does a better cable will help me get better reception? If so, wich one should I use?
5) Will reception be increased if I add more poles? If so, how do I do it?
6) I read in the tutorial that lowering the impedance of the dipole will help to improve reception. Exactly how do I do it with this design of mine? Because I did'nt understand exactly what does that meant.
7) Is there a better design available that will help me achive better reception?
My english is not so good so this post may contain gramatical errors. Let me know if you don't undrestand something.

I hope that somebody will help me with this soon. Feel free to use the design if you wan to. Thanks for reading this.
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PDAPhone Hacker Team

Posts: 777

Joined: Tue Jan 04, 2005 5:58 pm

Location: Grand Prairie

Post Thu Aug 28, 2008 5:37 pm

Re: How can I optimize a homemade 1900 mhz outdoor dipole antenn

Wow, why did you post this in general!? I'm sorry we've missed it so far, this is a excellent post and spymongoose I'm sure will chime in. I'm gonna move this to electronics (I guess I need a hardware forum... hmm).
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Shadowmite

Newbie

Posts: 1

Joined: Sat Sep 27, 2008 10:19 am

Post Sat Sep 27, 2008 10:27 am

Re: How can I optimize a homemade 1900 mhz outdoor dipole antenn

The antenna construction guide. . .very comprehensive. However, for someone such as myslef with 4 kids and no time to build this antenna. . . is there anything available for retail purchase for the MV430i device? Thanks-

Newbie

Posts: 2

Joined: Mon May 18, 2009 10:41 pm

Post Tue May 19, 2009 1:23 am

Re: How can I optimize a homemade 1900 mhz outdoor dipole antenn

:drinkers: exellent tutorials, thank you.

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