How can I optimize my 2.4GHz Link?

[CCTV_Solutions 0]

Hello all,

Found this forum doing some research online. Glad to be here, looks like a great place!!

 

I have just installed a simple system with 2 cameras that are located in a truck yard. Because I could not get cable to them for video I figured I could use the simple 2.4GHz TX/Rx systems. Of course as you already know these are not quite that simple. Does anyone have and tips for maximizing reception. Im getting a little bit of static on the screen. Its only about a 100ft LOS from TX to RX and I seperated the transmitters by 150 ft so they didnt kill each other. I am using the standard "rubber duck" andtennas that came with them.

[Rooney 0]

Are the transmitters and receivers addressable? If they are, make sure they are on different channels. If not, you are probably getting cross feed. Try to isolate the 2 different systems from each other by shielding the antennas so the rx is only seeing the tx for that rx.

[wisp_engineer 0]

Having two different RF links means you need to have each link on its own channel. There are 11 channels available in the unlicensed spectrum here in the USA.

 

There are only 3 useable channels: 1 6 and 11

 

You can however use a combination of 11 channels, like 2 and 7 or 3 and 8, or 10 and 2, etc etc. You need 4 channels of separation in the middle, to really ensure you do not run into interference problems.

 

 

Keep in mind that there are other 2.4GHz products out there so you are contending with those as well.

 

 

Having rubber duck antennas on your transmitters puts another nail in your coffin, as you not only hear the transmitter on the other end that you are supposed to hear, but every other 2.4GHz transmitter and device in that frequency range as well. This is why I advocate (and engineer my own jobs) using sector antennas and high-gain directional antennas like yagi's, panels, and dishes.

 

 

 

So.... Step one: see which channels you are on and try and change them around, but make sure you have adequate spacing between them.

 

Step two: Try and see if you can do a spectrum analysis in your area to see what other devices are in operation and on what frequency. Doing this may help you in deciding what channels to pick for your equipment.

 

Step three: If one and two does not help, try a more directional antenna on each radio. Maybe start out with a low-gain yagi, perhaps maybe a 9dB or 12dB model on both ends. You can also change the polarization of the antenna so it runs horizontally. This helps in that most sources of interference (like 2.4GHz routers and what not) are vertically polarized. You will get 25dB or so of isolation doing this. It will help out immensely if you are experiencing interference to do this.

 

 

 

Come back for more questions/answers if one and two do not work out, as there is a bit more planning involved to do step three.

[CCTV_Solutions 0]

The transmitters are addressable 1-4. I used channels 2 and 4. I will try 1 and 4. I also tried disconnecting one of the transmitters and still got some minor interferance, so im not sure its the transmitters beating each other up. I will try to get some panel 2.4 ghz antennas, but my dealer (Eclipse) has been sold out/backordered for 2 months so far....

[wisp_engineer 0]

What kind of connector is on the radio?

 

N or SMA?

[CCTV_Solutions 0]

sma

[wisp_engineer 0]

Sounds good. You'll need to identify it as to what gender the SMA is.

 

 

Here is a small panel antenna that might work for you. This one has an RP-SMA on the jumper:

http://www.hyperlinktech.com/item.aspx?id=1819

 

And here is one with an SMA on it....

 

http://www.hyperlinktech.com/item.aspx?id=1823

 

 

 

There are also a variety of yagi antennas available:

 

http://www.hyperlinktech.com/familylist.aspx?id=149

 

 

Are these cameras outdoors on a pole or inside a building?

[CCTV_Solutions 0]

Those look great, and good pricing! They are outside in 2 locations, I ran about 100ft of coax off each one to the TX right to the fence line closest to the building. That way I only have about 120 feet of LOS transmition. I was trying to get a good signal, guess that didnt work as planned. Ill get a picture and post it.

[scorpion 0]

If you are into projects??

 

http://www.wireless.org.au/~jhecker/specan/

[wisp_engineer 0]

Nice find Scorpion. These are awesome too, especially at their price point. Anyone using 802.11b/g equipment should invest in one if they cannot afford the price for a regular analyzer.

 

http://www.metageek.net/

[wisp_engineer 0]

OP, you said you ran 120 feet of coax to the radio is that right? This is RG59 for the video, not for the RF link right?

 

 

 

Those antennas are quality antennas for the price. I think they would even outperform the antennas that you are looking at ordering, but that is hard to say.

 

 

Just what ever you do, do not add amplifiers.

[CCTV_Solutions 0]

Correct

As in

 

CAM<======120ft coax======>TRANSMITTER w/antenna <--100ft LOS--> RECIEVER

 

Any good ideas to shield the rubber duck antennas from other 2.4 interference? Im just trying to wrap this project up already..... Any sorft of metal housing to block RF from other directions??!

[wisp_engineer 0]

You'll change the radiation pattern if you try and shield the antennas from interference. This may or may not be good. You could skew it all messy, and add in reflections which would cause serious problems.

 

 

Get some external antennas on those radios if you at all can. 100 feet pure LOS to the eye and to the radio should be cake with some directionals. I've got some 30 mile 2.4GHz links that have run for years that distribute internet to far-off locations. Keep in mind that these use directional antennas (big antennas, not yagi antennas) and special 2.4GHz radios. 100 feet is nothing.....

 

 

I'd like to see some pictures so that I can suggest exactly how to proceed with the install.

Edited June 19, 2008 by Guest

[wisp_engineer 0]

Check your private messages too.....

[wisp_engineer 0]

How is everything going? Any updates?

[cocacola 0]

I have got a much better solution than the others..

http://www.dealextreme.com/details.dx/sku.12215

 

Will boost transmitting power and will boost reception to.

Use the standard 3db antenna, to get a better dencer range than 8~12 db antenna's

 

Bottom line, one or two of this units is only you need.

[wisp_engineer 0]

While that booster might appear to be better, and it may or may not help it will for sure pollute the RF spectrum. This makes it more difficult for others to use the spectrum efficiently.

 

 

Higher gain directionals would solve the issue, and keep the spectrum usable should the OP need to install additional cameras, or should someone else might need to put some other WIFI on the air.

 

 

The "big hammer" approach to RF should never be used unless you know exactly what you are doing and completely comprehend the potential issues it can cause.

[cocacola 0]

While that booster might appear to be better, and it may or may not help it will for sure pollute the RF spectrum. This makes it more difficult for others to use the spectrum efficiently.

 

 

Higher gain directionals would solve the issue, and keep the spectrum usable should the OP need to install additional cameras, or should someone else might need to put some other WIFI on the air.

 

 

The "big hammer" approach to RF should never be used unless you know exactly what you are doing and completely comprehend the potential issues it can cause.

 

8~12 bdi gain antenna's cover a lager aerea, than the booster solution whit 2/3 dbi antenna's, but the range of the boosters will be more dence. So rf pollution will be less.

Anny way 500mW (thats max) in not mutch @t all.

a 12 bdi omni will give witt 100mW input more than 1.5 Watt (1.6 to be correct) 100mw=20 dbi+12 dbi=32 dbi=1.6 Watt

Whit 8 dbi omni antenna 20dbi+8=28 dbi= 630mW

 

See my point, the booster is not so bad @t all, and has a littel booster for incomming signal to!

 

dBm Watt

0 1.0 mW

1 1.3 mW

2 1.6 mW

3 2.0 mW

4 2.5 mW

5 3.2 mW

6 4 mW

7 5 mW

8 6 mW

9 8 mW

10 10 mW

11 13 mW

12 16 mW

13 20 mW

14 25 mW

15 32 mW

16 40 mW

17 50 mw

18 63 mW

19 79 mW

20 100 mw

21 126 mW

22 158 mW

23 200 mW

24 250 mW

25 316 mW

26 398 mW

27 500 mW

28 630 mW

29 800 mW

30 1.0 W

31 1.3 W

32 1.6 W

[CCTV_Solutions 0]

All thats going to do is send a bigger signal to the rest of the neighborhood. I have 1/2 watt transmitters, and all they have to go it 120 feet.

[mcs 0]

D link have a booster you can buy which is basically a repeater...

[cocacola 0]

All thats going to do is send a bigger signal to the rest of the neighborhood. I have 1/2 watt transmitters, and all they have to go it 120 feet.

No a 8~12 dbi antenna is a pest neighborhood. better one booster whit a small 2/3dbi antenna for a denser signal that a pancake flat signal thats goinig for miles.

[wisp_engineer 0]

Actually a directional is better for ANY solution where you must communicate between just two devices..... Period. There are times for omni-directional

antennas and the OP's situation is not one.

 

I work on multi-city-wide wireless networks every day. I install and troubleshoot point-to-point and point-to-multipoint networks as well. I have a firm grasp on where power amps should and should not be used. I think I know when/where various types of antennas should be used.

 

This is a situation where it could possibly cause harm to the existing 2.4GHz spectrum as well as the OP's system.

 

 

 

CCTV_Solutions what was your outcome?

[cocacola 0]

Actually a directional is better for ANY solution where you must communicate between just two devices..... Period. There are times for omni-directional

antennas and the OP's situation is not one.

 

I work on multi-city-wide wireless networks every day. I install and troubleshoot point-to-point and point-to-multipoint networks as well. I have a firm grasp on where power amps should and should not be used. I think I know when/where various types of antennas should be used.

 

This is a situation where it could possibly cause harm to the existing 2.4GHz spectrum as well as the OP's system.

 

 

 

CCTV_Solutions what was your outcome?

 

how can it possibly harm when the out put signal is lower than a directional antenna solution.

Also it cost a lot to try diversity of antenna`s intill you got the right one's.

My solution is anyway working, easy to install, cheaper, less output power, and smaller to!

 

I work weekly whit 2.4 receivers, antenna's and boosters.

I know a dens signal is really important for reception otherwise you can get distortion from 2.4 ghz devises.

 

The booster is a really cheap solution, i do not know why a expensive experiment whit antenna`s should be the better sollution...

(you know what connectors, coax, antenna's co$t!)

[cocacola 0]

Here is a link to a antenna that will fit on your receiver (connector F and not sma) http://cgi.ebay.com/Receiver-Transmitter-Antenna-4db-for-camera_W0QQitemZ300163665807QQihZ020QQcategoryZ48637QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[cocacola 0]

I really like the stock antennas in combination whit the booster unless you have a specific fixed application

 

There are a couple problems using higher gain antennas in your situation. The first (detailed below) is loss of gain in the vertical and immediate surrounding area. Second is the loss in the cable and connectors - you lose significant gain in every foot of cable, and in every extra connector - stock antennas have no cable and only one connector.

 

When you use a "higher gain omni" antenna, you are actually losing gain from other directions (the sum of omnidirectional gain in all passive antennas approach the same value - therefore you are always correspondingly less omnidirectional the higher the antenna gain.) A higher-gain omni flattens the coverage area and/or decreases/eliminates gain for close proximity. True omnidirectional coverage is zero gain with the antenna in the center. Obviously all omni antennas have gain - so the coverage looks more like a doughnut. The higher the gain, the flatter the doughnut and the larger the hole is in the middle (the middle being where the antenna is located.)

 

So, long story short, I like the stock antennas, they have just the right balance for the dynamic conditions in a vehicle, house or fixes close position. They also have only one connector loss, and no cable loss.