Antenna query

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linw

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#24353 22-Jul-2008 09:33

A client has several machines with only minimal wifi signals getting to them. Has anyone experience with replacing the PCI wifi card stub aerials with an extension 5dBi one? The original aerials are often tucked behind the metal PC box so it is feasible that an extended one, placed in line of sight, could give an improvement.

Any other suggestions welcome! (Using a WAG200G broadcasting across an outside alleyway to this 'problem' back office area).

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#150157 22-Jul-2008 10:44

Using higher antennas will help, these are good value. However why not trying to cable the office, or at least cable from the current source to the office and place a AP in the office. Using Wifi for commercial connections is not really a good idea, better using cable, why, well its secure, guaranteed throughput, no lags and its cheaper.

Cyril

linw

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#150204 22-Jul-2008 11:51

Thanks for the reply, Cyril. Those look like the $22 ones on Trademe I was looking at.

I am 100% on your side re cable v wireless. I would VERY much like to run a cable and attach an AP but I can't see any way to run said cable through two (landlord's) walls and across a public covered alleyway.

My client is willing to stump up for another broadband account to fix the problem but it does seem a waste of money! I am buying a new draftN modem/router to see if the mimo gets us a better signal. If not, it can serve the backroom on a phone line. Might buy one of the extension antennas to try it as well.

Cheers.

iainw

75 posts

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#150665 23-Jul-2008 15:12

I find the comments regarding wired vs wireless rather amusing.

Less Secure? Because of the inherently insecure nature of wireless technologies, most 'enterprise' wireless networks are actually more secure than a wired network. How many wired networks encrypt EVERY single packet? How many installers will configure 802.1X port authentication on a wired port? Unsecure networks are due to the way in which they have been installed, not the technology.

More Expensive? Sure, if you only require a single connection... Wireless offers the same 'oversubscription' advantages that allow ISP's to operate profitably. You don't NEED 100Mbps for every user all the time, however wired networking requires a port to be installed for EVERY possible workstation. This involves cables, cabling costs, switches... In contrast a single Wireless AP can provide connection for upwards of 20 users (assuming you are using decent equipment), most of whom will not notice any significant performance drop versus the wired network. Especially if you are using 802.11n Draft 2.0.

Like it or not, fairly soon networking will be wireless by default, wired by exception.

cyril7

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#150670 23-Jul-2008 15:22

some points I agree on, however a cable within a building is less likely to be intercepted, where as a WiFi is easily. Not all commercial operations have IT departments or outsoucing that ensures security is working and in place.

Better drop a line to Krone, Molex, or 3m and tell them to stop drop their copper and fibre business product lines, WiFi is coming.

Cyril

iainw

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#150673 23-Jul-2008 15:29

Don't get me wrong, wires are always going to be around - the day we start pumping 10Gbps through wireless is the day I go buy myself a tinfoil helmet.

However for network access, wires are on the way out. Already we are seeing business deploy networks that are entirely wireless. And I'm not talking about 2-3 man businesses, Im talking about 25,000 user university campuses, where everything is Mesh and P2P microwave links...

Intercepting an 802.11 signal is irrelevant if it has been configured correctly. And I have little sympathy for people that deploy something they don't really understand, and get it wrong.

linw

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#150855 24-Jul-2008 09:33

I agree with a lot of your points, iainw, but many of us have the problem of inadequate signal range. In my case, a cable attached AP would fix this. Pity I can't run a cable!

bleater

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#151350 25-Jul-2008 16:22

I've messed around a lot trying to solve similar issues. Forget hi-gain wifi antennas; more trouble than they're worth. Get yourself a $20 USB wifi stick and a $10 10-metre USB cable. Put the stick on the end of the USB cable, and position somewhere where you get better reception than the little wifi pigtail on the card on the back of the PC.

If you're really keen, you can stuff the usb wifi stick into a pringles can, and improve the gain at the expense of omnidirectionality.

Samsung

Shop now on Samsung phones, tablets, TVs and more (affiliate link).

pando

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#151991 28-Jul-2008 09:46

I completely disagree that wires are on the way out when they're outperforming wireless 15:1 in my setup, gigbit LAN, wireless G and N, laptops are G so get 25mbps yet wired will rock 400mbps (using monitor program to see actual data throughput). For internet gaming and streaming video the wireless desn't cut it.

My house is networked to my neighbour's via underground cat6 and mine is then networked to another two houses away using 2 wireless units to bridge. I'd say security is more of a worry at the wireless end, even running WPA-PSK, MAC filtering, and no SSID broadcast - a determined hacker can still get in through the wireless but good luck trying to get on through the wired section without breaking in to a house which is highly pointless.

Also, given that houses inheritly have walls, getting strong wireless signals through them is never going to happen, so internally connections are fine, but you try bridging two houses 70m apart, the end result is having to spend $$$ on decent equipment. If only we were allowed to run a cable under the road, would've been far cheaper and more reliable.

Sorry if this is going OT.

iainw

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#152000 28-Jul-2008 10:22

As I said - wireless security comes down to the way in which the network is configured. MAC filtering and no broadcast SSID are not security measures. WPA-PSK is the absolute minimum encryption you could consider as being semi-secure.

There will always be a need for wired networking in the network core, however for access and distribution, the cost benefits of wireless are significant. It is also a matter of scale - home use of networking technology is a very small portion of networking technology. More and more, people expect to have anywhere connectivity, which cannot be delivered via a wired edge.

linw

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#152052 28-Jul-2008 13:43

Some follow-up.

Thanks for the suggestion, bleater, re using USB devices. I have one of those but haven't tried it as suggested.

The WAG160N was installed today with mixed results. The signal was improved a little, but most of the backroom devices were only showing 2 bars of signal strength. However, a new Dell machine which had a Dell installed PCI wifi card, was showing all bars lit. This card shows as a "Broadcom 802.11G" device in device mgr. All the weak connections were using DSE NIC's.

Mmmmm... Is there a big difference in wifi cards as this situation suggests? What cards should one buy? (I will try my USB device, though).

Another "interesting" finding was that with the WAG160N no one using a wireless connection could connect to Interspeed's pop server but http was OK. However, one machine on a cable could. Put back the WAG200G and all back to normal. WTF???

Here at home I am using the 160N and can get pop3 traffic no problem via a USB wireless device so it is a mystery to me.

Lindsay.

Edit:- I have just confirmed that the Dell machine quoted above is back to two bars with the WAG200G in place. This clearly suggests the Dell NIC is able to take advantage of the N router. Now, if I can find out what NIC they use.......

iainw

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#152059 28-Jul-2008 14:05

There can be a huge difference in the performance of different 802.11 cards, and access points, and this is one of the key reasons why equipment like Cisco, Motorola, Aruba is so much more expensive than dLink, Linksys, Netgear etc..

The specs that tell you how good it will be are:

1) RSSI thresholds. Every 802.11 card/access point in existance, should have a known and published set of thresholds. This is a list of pairs - -xxdBi signal strength, and XXMbps data throughput. The data rates are standardised - these are the supported rates for 802/11a/b/g depending on which protocol you are using. Ideally, you want the numbers as low as possible, ie as highly negative as you can. This tells you how strong the signal needs to be to achieve a given data rate. eg Motorola's AP5131 has a 54Mbps, 802.11g threshold of -70dBm. This means the signal has to be at LEAST -70dBm in strength to achieve 54Mbps.

2) Antenna Gain. The higher the better. every 3dBi gain, equates to a doubling of the transmit strength, a 10dBi gain equates to 10x the transmit strength. This ALWAYS comes at the expense of coverage.

3) Transmit Power. This is a figure in mW, and is fairly obviously, the amount of energy the radio itself transmits with. This is one of the biggest differences between consumer access points and enterprise access points.

To give you an example of the difference the equipment can make - a Netcomm RTA1046VW access point has a mximum transmit power (Radio and Antenna of 13.5dBm, or a littel bit less than 25mW. A Motorola AP5131 has a maximum transmit power of 100mW, before adding in antenna gain. The 'worst' antenna that you would typically connect to this AP is dBi. This gives a maximum transmit power (Radio and Antenna) of 160dBm - or 6.5x the power.

This is one of the biggest reasons you will not (should not) see any equipment that is sold in Dick Smith's deployed in large scale wireless deployments.

If you REALLY want to know whether a deployment will work, there are some fairly simple mathematical calculations that will let you work this out, before even having to deploy.

cyril7

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#152078 28-Jul-2008 14:54

This gives a maximum transmit power (Radio and Antenna) of 160dBm - or 6.5x the power.

Its also 10trillion watts, I dont think Transpower has enough supply for your demands, also be aware this is 2.4GHz, which is absorbed by tissue very readily, were all dead, maybe those nasty Dlink routers are just fine.

Cyril

iainw

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#152092 28-Jul-2008 15:10

oops, well spotted. 160mW not 160dBm. Where's my tinfoil hat....

linw

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#152688 30-Jul-2008 14:01

Some good progress, but also some confusion! The Dell card is an ASUS WL-138 variant. It is confusing as it has two models written on it. These are "WL-138G V2" and "WL-138-gE). ASUS and retailers show these as two different products. The 138G is only $30 and the gE is about $10 dearer. The gE is supposed to have extended speed and range. Rx sensitivity for gE is -73 to -75 dBm and -69 to -71 dBm for the G.

Perhaps either will work well but it may be better to get the gE ones? Anyway, if anyone is looking for well performing cards, they could look at these.

Comments welcome!

linw

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#152728 30-Jul-2008 16:20

Also looking at the CNet CWP-854 adaptor. Anuone with experience of this one?

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