Making a corner reflector for Wilson Trucker omni?

thebordella · EVDO User Joined: 12 Mar 2007 Posts: 26

I am experimenting with (cheap) ideas to squeeze out every dB I can get in a fringe coverage area.

Currently using a Wilson Trucker omni on the roof. Soon going to raise it for more elevation. I'm intrigued by the DIY corner reflector described in another post:

http://www.evdoforums.com/thread5179.html

Suppose I want to place the Wilson omni in the PCS focal point of the corner reflector. Which part of the omni is the "hot" part? This antenna has a 'whip' at the top, with a bulbous thing partway down (load coil?), and then more 'whip' antenna, below which are several metal spikes which supposedly act as a ground plain.

Where would you orient the Wilson omni inside the corner reflector construct? Does this plan even make any sense?

I can't/won't place the USB720 itself in the corner reflector, as proposed in the original post, because this needs to be mounted outdoors.

thanks!

n6gn · Posted: Thu Oct 04, 2007 10:58 pm Post subject:

Try placing the length of the omni, both above and below the "thing", along the line where you would have placed the dipole or U720, had you used that instead. This means that you want the the whole thing spaced out from the corner about 2" at PCS and about 4.5" for 850 MHz. The presence of the corner (correctly aimed) should increase the overall gain of the omni by 6-8 dB. You'll want to be sure that the overall height of the corner is at least 2-4" greater than the length of the omni to get this improvement.

n6gn

118morpheus · EVDO Newbie Joined: 05 Jan 2008 Posts: 4

I wondering how the reflector worked for you if you tried it out. I have a few q's for an expert. I noticed a distance of 2" from the corner was mentioned. Where is that derived from (why 2").

I've done some research on corner reflectors and for a 1920Mhz corner reflector. The research i've come up with says that the best position for the element is .6 wavelength from each panel. If a 1920Mhz wave is 156.25mm then a .6 wave is 93.75mm. The distance from the corner is about .85 Wave or 132.56mm...much farther than 2". These numbers were calculated based on specs for a "3D corner reflector" found here:

yu1aw.ba-karlsruhe.de/shorten3dcra.pdf

I don't know if the difference is that there is a bottom reflector???

I have a wilson trucker as well and want to make it a little more directional with some signal gain. I was going to put the element for the trucker at the distances I calculated from the pdf file above, but am wondering if the 2" would work just as well.

Any guidance would be helpful. Or even refer me to where I can find some measurements for a corner reflector in the PC band 1850-1990Mhz

thanks

rlw · Posted: Sat Jan 05, 2008 11:40 pm Post subject:

Take a look at http://www.evdoforums.com/viewtopic.php?p=39708#39708 -- I made my 12 db parabolic reflector based on the designs at http://www.freeantennas.com. I'm also in a fringe area -- I was getting 400-500kbps downloads before I used the reflector, now I get 800-1200kbps and 300-400kbps up.

Be sure to use some kind of ground plane (I use an old aluminum modem case).

Hope this helps,

RLW

n6gn

118morpheus · EVDO Newbie Joined: 05 Jan 2008 Posts: 4

Excellent response! thanks for the info. I figured the 3D had a difference and noticed that the direction of the signal radiation was about 45 degree from the bottom plane.

Do you suggest any place for DIY cone antenna. I am working on building a bi-quad with 1920 specs and may try to use it as a feed with a dishnetwork antenna or just alone. But It seems that the bi-quad is a little picky with dimesions and building. We'll see how it goes.

Do you know why 2" is the sweet spot on a 2D corner reflector. Is a a percentage of wavelength or some other variable?

Thanks again,

Jim

n6gn · Posted: Sun Jan 06, 2008 2:56 pm Post subject:

118morpheus · EVDO Newbie Joined: 05 Jan 2008 Posts: 4

Thank you. I finally found someone with an understandable answer!

Jim

Jayson · Posted: Sun Jan 06, 2008 6:43 pm Post subject:

118 I would like to see this project if you get it finished up ....I to live in an area like you speak of.... always looking to better my downloads....normally there around 500 down and only about 100 up.....thought of buying a grid antenna maybee in the near future to see what i can get outta that !!!!! hope to see your results soon !!!! and good luck with it ...... Smile

118morpheus · EVDO Newbie Joined: 05 Jan 2008 Posts: 4

Just a little info about my connection. For the past month since signing up for sprint evdo using a pantech px500 and Kyocera kr1 I had been getting 400-900k down and 150-170k up.

My signal with card in my laptop is -89 to -87 and pings from 85 to 175ms (prett good) with a Wilson trucker on roof, and 30 feet of RG8 ultra low loss (heavy stuff). Signal is going through tree tops to tower about less than 2.5 miles away. My router's signal meter is next to useless. It fluctuates from 3 of 10 bars to 7 of 10 bars even though when the card is in my laptop the signal is steady according to Sprint Connection Manager.

The past three days I have had erratic pings and speeds from 150-700k down and 80k to 170k up with pings 99-350ms. I have also had several unexpected disconnects where I have had to restart the router and reconnect.

I got a CM2000 3/2 watt dual band amp 2 days ago, it doesn't give me any gain increase...still -89 to -87.

Today 1-6-07 I put a parabolic reflector on my wilson trucker. I didn't check the db gain in my laptop using connection manager, but I got a more steady 8 of 10 bars on the router signal meter, with drops to 3 on occasion (don't know why?). Before reflector I got 6 of 10 bars with drops to 3.

Speed tests are still about the same as the erratic speeds and pings I had been having over the past few days (sprint says all is ok on their end).

Another odd thing I have going on is my pantech says I am connected to rev A when looking in the diagnostics window of the connection manager, but I was told by a local Sprint employee that my area has not yet upgraded to Rev A? My uploads lead me to believe I am not rev A.

In my case signal increase does not appear to equate to faster speeds.

Sorry about all the boring info. I just am wondering why my quality of service took a dive and wish could get an upload and download speeds to be like some others 1300 by 400+.

Since this is a thread about reflectors:

The parabolic reflector I made was of 1/4" wire mesh the bottom rests on the "ground plane" (metal rods) at the base of the trucker antenna. The reflector is set for 1.6" which is the focal point for my particular parabolic antenna. It seems to work, but has not changed my speeds any.

xrayman · Posted: Sun Jan 06, 2008 11:59 pm Post subject:

n6gn · Posted: Mon Jan 07, 2008 1:45 am Post subject:

xrayman · Posted: Mon Jan 07, 2008 11:09 am Post subject:

n6gn,
Thanks for the elegant technical reply.

matt10099 · EVDO Fledgling Joined: 09 Dec 2007 Posts: 15

I also live in a fringe area with trees.. I have a 7db gain 18" antenna, which I made a corner reflector with dimesions of approx. 20"H x 17"L, with plywood surfaces, then covered in aluminum foil for the reflector

I now get very good to excellent signal or 4-5 bars (-77--81db)

Getting that signal was very hard it took 2 people & about 1-2 hrs of adjustments to get right... there was little room for error & 1/8" meant the difference between a good signal or low signal.

Very cost effective solution if you already have these supplies & 2 people & couple hours.