802.11 antennas using a splitter

Question

802.11 antennas using a splitter

mpiteo (Electrical)

(OP)

1 Jun 09 11:23

I have an application where I need to install a repeater, 2.4 ghz 802.11 ethernet radios. I have received conflicting information regarding the use of 2 antennas and a spliter. The radio techs suggest a Omni to Omni on the base run, and adirectional to the omni from the source location, with the comment:
"You should not use an antenna splitter with a half duplex TX/RX signals"
An antenna supplier advises using a splitter with identical antennas & cable length will have about a 3.5 db loss, but allow use of directional antennas at both locations.

Any advice?

Higgler (Electrical) · Answer 1 · 2009-06-01 17:17:58

Here's a discussion of a simple 802.11 repeater product that increases range from 55 feet to 140 feet in their example.

http://www.wi-fiplanet.com/tutorials/article.php/1571601

kch

mpiteo (Electrical) · Answer 2 · 2009-06-02 08:16:13

The radio I am using has a repeater funtion, in this case we are trying to establish ethernet for security cameras. The source is below grade (about 100') and 400' from the repeater which is a 15' above the level of the damn. The base radio is 1/2 mile away across the reservoir.

My question is about the use of a splitter with directional antennas, one pointed at the source and the other across the reservoir at the base radio.

The radio techs suggest a Omni to Omni on the base run, and adirectional to the omni from the source location, with the comment:
"You should not use an antenna splitter with a half duplex TX/RX signals"

An antenna supplier advises using a splitter with identical antennas & cable length will have about a 3.5 db loss, but allow use of directional antennas at both locations.

Any advice regarding the use of the splitter?

Higgler (Electrical) · Answer 3 · 2009-06-02 17:10:03

I think I understand, let me explain what I think.
You have the options of one omni antenna, and no splitter, versus two directional antennas with a splitter to connect one base station with a single camera and you have a repeater radio in between the two.

A typical directional antenna if you purchase a standard directional gain at 24 dBi (http://www.radiolabs.com/products/antennas/2.4gig/2.4-aluminum-parabolic.php only $70), take off 3 dB and you get 21 dBi. Compared to a Terk 12 dBi omni you've picked up 9 dB for your system. (link to a Terk omni http://salestores.com/trendn117.html and under $100). You could try some math to see if it'd work.

I'd say buy the $100 Terk antenna, it's very simple to mount compared to the higher gain antennas and the wind won't blow it around much (I think), put it up and find out quickly if you need more gain. When you do a test trial, change the height of the Terk antenna up and down in increments of 1 inch, bounce off the ground can make ugly results.

What's your range now? Has anyone done some math for you?

kch

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802.11 antennas using a splitter