Getting the maximum range from a 15 dbi Antenna

Getting the maximum range from a 15 dbi Antenna

I wanted to run this scenario to you guys before I set everything up in case I am overlooking anything.

Here are the parts that are being used in this situation:

Linksys WRT54G version 5 with DD-WRT v23 SP2

Omni-directional 15 dbi Antenna

Lighting Arrestor

RP-TNC to N-connector pigtail (1ft)

50ft LMR 400 N-connector on both ends

Here is how I plan on setting up everything.

From the wireless router I will configure the router to use one antenna for Transmit and Recieve.

Then connection the pig tail to the router . Then connect the LMR to the pigtail.

This cable will lead up a 30ft pole on the side of my house to the Lighting Arrestor then to the 15dbi Antenna

Setting up everything like this how much range do you guys think I would be able to get as long as am

in line of sight of the Antenna?

Is there something that i am over looking that can enhance this wireless connection?

If you guys know over any websites where i can get pics on how to set this up I will be most appreciate of the website links also.

Also looking for websites on how to tie the Antenna pole to the house

Thanks in advance

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Isn't there some way you could mount the Linksys box closer to the antenna and avoid 50ft of coax. Granted it is the good stuff, but still, it's 50ft.

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Adair Witner

We have had good connections from several km's away with a directional yagi antenna not knowing what the other end was using ( Hotspot ). This yagi is supposed to give 17 dB but I don't know for sure. I can buy a 15 dB omni here too but I doubt it will give that much, since the directional antenna's are about the same.

Well I did solder a female powerplug in two of the spare wires on the UTP cable en a male plug on the other end and used the original power supply from the linksys for feed, not sure if this is the way do do it but with a 20 meter long UTP cable it works perfect POE :-). Now I /you can mount the linksys in a box with an antenna connected straight to it, so no more cable losses. There are even two more spare wires in the UTP cable which can be connected to the reset button, then you can reset from the ground too. Unfortunately we have to open the linksys case for this connection.

One other thing is removing the antenna selector chip from the PCB, I don't have the guts for it but a big boost in receiving from week signals is reported. Much more gain then the 2 to 3 dB the chip itself would "eat".

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Hi. I'm doing something similar (see "wireless on the ranch" topic), so I'm interested in your plight and also can share what I've sorted out so far.

Actually, it appears that you will use DD WRT MICRO. Special installation instructions. You knew that, right?

You know that a 15 dbi omni will have a very, very narrow beamwidth, right? It is a disc-shaped beam.

It's important to know where you want your signal to go. Do you really need 360 deg coverage? Or more than, say 120 degrees? What is the height difference and distance between the points?

Don't know, but I'd consider setting the pole in a concrete post hole then use U-bolts and a wood spacer or "stand-off" (if necessary) and attach to the fascia, somewhere where there are no gutters. 30 feet is pretty tall. How high is the attach point on the house? May need guy wires.

Arrestor then to the 15dbi Antenna

Isn't the lightning arrestor supposed to be where the cable enters the house? Between the LMR-400 and the pigtail, right? That's what I read.

able to get as long as am in line of sight of the Antenna?

Depends on your other antenna, no?

There are calculators for this, called "System Operating Margin"

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I think that you can assume 16db transmit power to start (up to 20 db boosted) and also need receiver sensitivity, um, I think -83.

I am figuring about 3 db loss for a 30ft lmr400, arrestor and pigtail. (.25 per meter plus connectors) You might add another 1 db since you are 20 ' longer, so 4 dbi cable loss.

Anyway, plug in the numbers and play with distance, making sure that you have 20 db or better SOM. If it calculates below that, you are out of range for reliable signal.


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Most likely at 30 foot with a 15dB omni, you will be too high as with gain like that, the radiation pattern is "flattened out" considerably. Look very carefully at the vertical radiation pattern and you may reconsider the need to put it so high. The closer clients will certainly end up "below the radar" and have disappointing results.

The lightning arrester should be at the AP end of the cable and have a good heavy earth lead to ground to be effective at all.

Our own case has been a similar omni at 14 foot over a predominantly flat terrain and reliable coverage has extended some 0.75 mile with odd spots extending almost 2 miles, albeit with marginal signal. The AP is located so that there is only 6 feet of LMR400 cable between it and the antenna.

Fitting a "booster" amplifier will put you into the realm of the alligator and such devices do not adequately compensate for a low return signal from the client, despite manufacturer's claims.


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