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Billy Brethr

join:2005-04-01
San Antonio, TX

Wireless Router Antennas: Why Can't I Do This?

I want to cover as much open-air area as possible with good-quality wireless signal. I have this idea of connecting RG-6 cables to the wireless router, running the cables up the roof and zip-tying the cables & antennas to pole 5 ft. above the top of the top of the roof. Higher is better, right?

I've read a few things online, but no one seems to want to move the antennas to where they need wireless; they want to move the whole router, and this doesn't make any sense to me.



gatorkram
Need for Speed
Premium
join:2002-07-22
Winterville, NC
kudos:3
Reviews:
·Suddenlink

I'm no expert, but I think it has to do with the loss at those high freqs. You'd need some serious cables to do what you are talking about imo.
--
What the heck is a GatorKram? »www.gatorkram.com


LittleBill

join:2013-05-24
kudos:1

above poster is right, huge loss in the cabling unless using lmr type cable

if your doing it for outside usuage look at bullet or pico from ubiquiti, other wise u can potentially shoot over the client


LLigetfa

join:2006-05-15
Fort Frances, ON
kudos:1
reply to Billy Brethr

said by Billy Brethr:

I've read a few things online, but no one seems to want to move the antennas to where they need wireless; they want to move the whole router, and this doesn't make any sense to me.

Leave the router where it is. Install an outdoor AP powered over the ethernet.
--
Strange as it seems, no amount of learning can cure stupidity, and formal education positively fortifies it. -- Stephen Vizinczey


Billy Brethr

join:2005-04-01
San Antonio, TX
reply to LittleBill

said by LittleBill:

above poster is right, huge loss in the cabling unless using lmr type cable

if your doing it for outside usuage look at bullet or pico from ubiquiti, other wise u can potentially shoot over the client

How much loss? How far is too far?


John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:8

1 edit

You lose 10dB per 100 feet...at least.


LLigetfa

join:2006-05-15
Fort Frances, ON
kudos:1

1 recommendation

reply to Billy Brethr

»timesmicrowave.com/calculator/?p···=52#form



clarknova

join:2010-02-23
Grande Prairie, AB
kudos:7
reply to Billy Brethr

Other factors to consider when going outdoors is that APs designed for outdoor use typically have higher output power than your indoor router, and can have their ACK timeout lengthened to accommodate for further clients.
--
db



Billy Brethr

join:2005-04-01
San Antonio, TX

I think about this. I read an article that underlined the fact that antenna's "listen" as well as transmit, so having a powerful transmitter is only half the battle. Do they have separate "reception" antennas?



gatorkram
Need for Speed
Premium
join:2002-07-22
Winterville, NC
kudos:3
Reviews:
·Suddenlink

An antenna, is an antenna, for the most part, as long as its a passive system, and doesn't involve some type of amplification.

So in the most basic configuration, an antenna used to transmit a signal is no different than one receiving it.

I think the best way to cover a large area, would be with more than one radio, or more than one antenna on the transmitter.

A sector antenna for example, and then on the other end, something also directional, cantena or sector I'd guess.

Having a higher gain antenna on each end is helpful too. They won't transmit a stronger signal, but they will listen better.

This is my limited understanding of how things work.
--
What the heck is a GatorKram? »www.gatorkram.com



John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:8
reply to Billy Brethr

The flip side to ' a powerful transmitter' is a 'sensitive receiver'.

Remember, coax attenuation also reduces the received signal just as it reduces the transmitted signal. It cuts both ways...



clarknova

join:2010-02-23
Grande Prairie, AB
kudos:7
reply to Billy Brethr

Most APs will use the same radio/antenna combination to transmit and receive in alternation. There are exceptions, such as Ubiquiti's AirFiber, which has a pair of antennas and dedicated transmitter and receiver.
--
db


LittleBill

join:2013-05-24
kudos:1
reply to Billy Brethr

op its cheaper just to buy one designed for this lmr is very expensive. just do it right


HELLFIRE
Premium
join:2009-11-25
kudos:18
reply to Billy Brethr

Second everything that's been said so far :

a) remember high school physics : v = f lambda? With V being constant (speed of light), f going higher means lambda
going lower. What this translates to is the higher the frequency, the shorter the range.

b) cabling / joiners add attenuation to the signal... do you know how to calculate / account for that?

c) more powerful transmitter NEQ better signal... this can be illustrated conceptually by yelling a
conversation with a person sitting next to you and talking in a normal voice.

In any case, your questions are delving into radio theory that I haven't touched on the order of years.
You could knock around for a refresher source of information about this and see if that helps you understand,
or you could look into a CWNA book. Doesn't bore you will just physics, and is a pretty good wireless resource
overall.

My 00000010bits

Regards


switchman

join:1999-11-06
reply to Billy Brethr

To OP, FYI RG-6 is 75ohm cable while the typical wireless AP I/F is 50 ohm. If you really want to do this, get a »www.amazon.com/Ubiquiti-UniFI-Ou···UniFI+AP.



WHT

join:2010-03-26
Rosston, TX
kudos:5
reply to Billy Brethr

Assuming your are using street level laptops or smartphones, the optimum antenna elevation is around 12 to 16 feet above the ground.

I spec'ed out a system a month ago for 12 APs using VPOL omni antennas. I suggested 15 foot elevation,but they were installed at them 25 feet and the the signal shot over the client devices. They will be remounting the antennas at 15 feet this week.

Connecting the antenna to the AP with a long run of cable is really, really old school. Now the APs are mounted next to the antennas.

As for the AP antenna both "listen" and transmit, what is really happening the radio is continuously switching from transmit to receiver mode.

In almost all situations, you want to achieve your AP EIRP using a higher gain antenna, instead of increasing the transmit power level. 2.4 GHz FCC Part 15 radiators are limited to 1 Watt (30 dBm) transmit power and 4 watts (36 dBm) EIRP, which means you can use up to a 6 dBi gain antenna.

Let's look at two ways to get that 36 dBm EIRP:
30 dBm transmit power + 6 dBi antenna.
20 dBm transmit power + 16 dBi antenna.
In the latter you have increased your received signal gain by 10 dB (10 times) and still retain your 36 dBm EIRP.