Co-Phasing Wilson Trucker Omni Antennas?

Franksr · EVDO Newbie Joined: 14 Apr 2007 Posts: 5

I am a trucker and I would like to co-phase two of the Wilson Omni Cell Antennas. Is there a co-phasing harness available? At thre present time, I'm running streaming video using my Wilson Amp and one Wilson Trucker Antenna with my Sprint U720. Thanks.

shooter64738 · EVDO User Joined: 07 Sep 2007 Posts: 41

I haven't seen a harness, but this may help you.

This is how I did it for 2.4ghz.
Two 50 ohm antennas
Two runs of RG6 Coax (about 5 feet each for my purposes)
A two-into-one coaxial connector. I used an SMA because I had one already
A single SMA female connector to a 6 inch run of RG58.
A single TNC connector on the other end of the RG58 to hook to the router.

Connect antenna 1 to one run of RG6, connect antenna 2 to the other run of RG6, put both unused ends of the RG6 into the 2-into-1 connector. Connect the 2-into-1 to your modem directly if you can. I had to use a 6"pig tail of rg58 to get from the 2-into-1 to my router because of connector limits. I didn't see any real difference running duals, or single when I toyed with the wifi stuff (probably from some coax loss), but it did add some directional properties to the setup.

apco25 · Posted: Wed Nov 28, 2007 7:04 pm Post subject:

That's the old CB style of co-phasing antennas and really not appropriate for the these frequencies. Even if you do use this method the cable between the antennas MUST be a specific length for each side, not some arbitrary number and that's based upon the frequency. The method referenced was designed to improve the radiation pattern for semi-trucks based upon their large size and potential for oddly shaped antenna patterns with single roof or body mounted antennas as well as the "cool" factor of two antennas.

I doubt you noticed anything improve because it most likely degraded what signal was there.

Also, RG-6 is quite a lossy cable for these frequencies. Again a bad idea.

Every bit of RF needs to make it to the antenna when you're dealing with microwave frequencies and the relatively low power used in EVDO and Wifi.

shooter64738 · EVDO User Joined: 07 Sep 2007 Posts: 41

Well thats odd. RG6 should be ~6db attentuation per 100 feet @ 1000mhz. RG58 rates ~16db loss per 100 feet. Good quality cable will of course make a difference in any case.

I probably saw no improvment from insertion loss, in partuclar with the 6 connections being made. According to my (pretty old) antenna books, the coax length should be multiples of 1/4 wavelengths in odd numbers. 3 1/4 wave lengths, 5 1/4 wave lengths 7 1/4 wave lengths, etc. Maybe it's out dated, or maybe I didn't understand it.

Franksr · EVDO Newbie Joined: 14 Apr 2007 Posts: 5

I did receive this reply from Wilson Electronics:

"There would be no gain. If you add a splitter you’re going to lose 3 Db per side of the splitter. In a semi I would strongly suggest not using a splitter. If you have any further questions feel free to ask."

shooter64738 · EVDO User Joined: 07 Sep 2007 Posts: 41

I would have to agree after seeing no improved results from the setup I was experimenting with. I suspect a more directional setup wouldn't benefit you, since you want this in a mobile environment?

Franksr · EVDO Newbie Joined: 14 Apr 2007 Posts: 5

After we get the antenna connection to the U720, does it matter that much
whether it is plugged in direct to the USB port or not? I was using the split cable that came with it which plugs into 2 USB ports. The manual says to use the split cable if your on a fringe area, which must improve the output or the reception? I am using a WIlson Amplifier as well. I needed a little more length so I eliminated the split cable today using a standard USB Cable. How does the split cable going to 2 USB ports help and does it make any difference since I"m using an amplifier? Should I have used the extension USB cable with the split cable rather than eliminating it?

SlyFerret · EVDO User Joined: 19 Mar 2007 Posts: 70

If you can get ahold of RG-8 coax instead of RG-6, you might see better results. RG-6 is 75 ohm impedance cable, RG-8 is 50 ohm (which matches your 50 ohm antenna system).

RG-6 is for TV equipment. RG-8 is for radio communications equipment.

I'm with the group that says trying to co-phase these antennas is not going to help. The way the signals are modulated, you won't get a benefit.

-SF

shooter64738 · EVDO User Joined: 07 Sep 2007 Posts: 41

That’s correct, and I agree there won't be any fantastic results. But to co phase with that harness in the manner I understood he wanted to, 75 ohm coax is required for harness.

I am not advocating co-phasing. I toyed with it out of necessity in a wifi setup. I saw no gains in signal, but some gain in directivity.

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