Home made 14db gain Antenna


A good friend of mine made this antenna. I am not taking credit for it, however I will take credit for assisting him in the design and answering all of his questions at 3AM. >:o  He doesn’t have a website so I agreed to post it to mine.

 

“Hi everyone, Just to clarify first, this has been built to achieve maximum d/l speed on the Telstra Next G network. Australia. But it will also work for any service on the same frequency. They are :

NextG uplink to the tower … 839.8MHz
NextG downlink to your computer … 884.8MHz

 

So I started with what I had in the shed. An old Tv antenna .. has to have an outer circumference of 10mm to achieve this desired feed. I used Inch and a half PVC Box for my main beam which I had laying around.”

 

This is what I started with:

Used a square to keep the holes as perfectly aligned as I could. I done this around to the other side and drilled each side separately so I didn’t elongate the holes.

 

Put these 2 holes in so I could slot the bolts through easily to attach the coax.

Side view. I am happy that they are reasonably straight. If you are a few mm’s off Its okay, don’t scrap it an start again. If you are a shitty driller and do it at 45 degrees, you will have a problem.

Double checked to make sure they were joined properly and got the desired reading of 0.00. At this point, joining the drive element, Get a multi meter and check the Ohms, or resistance. This is crucial to make sure you have it all joined properly.

 

Finished!   Here is the end, what it should look like.

 

I got a bit pedantic and used some verniers to measure the 10mm tubing to make sure, and then used a 25/64 drill bit (9.9mm) provided a very nice tight fit. I used a blue plastic wall plug for the joiner also.

 

So after using Google earth and its ruler function to determine the correct line of sight to point my new antenna, After I had a rough idea and picked out a landmark, I went into town ( I am aproxx 27k from town and the tower ) to make sure what was near and noticeable, when I got home I used a high powered rifle scope to pick out the landmark ( I was within 10 degrees ) Pointed the antenna there, run a test … from ethernet and my wireless network. The difference was amazing. See below.

 

This was before with the standard BP3-EXT Modem.

This is with the antenna installed and pointed at the right tower.

With this gain I know I can tune it better as I am using RG58/U Cable @ 21metres. Research showed me, 10m RG58/U 50ohm cable @ 850Mhz = 4.61dB loss. So, I can make this better and cut my length in half.

 

The antenna design I chose after a lot of research was from http://www.perite.com/vk7jj/nextgyagi.html With the extra cable it equates to a 35% loss. So it is what I will work on.

If anyone wants anymore details, I’m sure the mods here can grab me and let me know.

I have to say some thanks to people you will not know, but, they helped with design, dimensions, frequency tracking, so thanks AudioNut, StraitVodka, Wahroonga Farm.

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