High gain aerial

[filbert]

I'm looking to improve the wifi connection on my pc that's got a pci wifi card, it's got the normal little black aerial that screws on the card at the back.
Do the high gain aerials work, and if so what's the best one to go for, I like the idea of one with a cable so I can point the aerial at the router, if this works better.

Thanks.

[matty-hodgson]

well i bought 2 huge hi-gain aeriels for my network.
1 for the pc and 1 for the router and i've not had any problems since then.
i only really needed them cos the house i live in has relatively thick walls (old house) and the router's the other side of the house, but they do definitely make a difference..

bought mine off ebay btw for £7 each IIRC

[Moby-Dick]

did the same - got a foot long one for my router - the connection is great throughout the house now.

[Funkstar]

You can get signal problems with them though as they change the shape of the signal area.

If you think of the signal area as a doughnut, increasing the power or adding a high gain antenna will increase the size of the outer edge, but will usually increase the size of the hole in the middle as well. They can also squish the area down so it doesn't reach as far up.

This usually isn't a problem, but in some situations it can be. Mainly if you have devices close to the router as well as far away. I've seen routers where you can't get a reliable signal in the room directly above, but you can in the pub across the road

[filbert]

Thanks for the replies, I can't put an aerial on the router, that's why I thought of one with a cable that you could point to the router.
Like Funkstar says the signal from an aerial is like a doughnut, I was thinking of a signal more like a slice of cake, lol.
If the normal high gain aerials work that would be the cheapest option, like this:
http://www.scan.co.uk/Products/Newli...s-(NLWL-ANTSMA
Or a directional one like this:
http://www.scan.co.uk/Products/Dlink...-SMA-to-RP-TNC)

none of the links work so the scan codes are LN11987 and LN17038

[matty-hodgson]

well the aeriels i have are exactly the same as this one and they work a treat

going on what Funkstar says though: if i carry my Netbook past my router, it always drops the connection, every single time, but other than that, the connection is absolutely amazing
i get an excellent signal quality and i'm at least 20-30m from my router with 3, maybe 4, thick walls in the way.

[Saracen]

I'm looking to improve the wifi connection on my pc that's got a pci wifi card, it's got the normal little black aerial that screws on the card at the back.
Do the high gain aerials work, and if so what's the best one to go for, I like the idea of one with a cable so I can point the aerial at the router, if this works better.

Thanks.

In theory, yes, high gain aerials work well. But you need to be a bit cautious about how you define "high gain". Gain compared to what?

Several antenna listed in this thread quote gain figures measured in dBi. Be very cautious about those (I mean about the figures quoted, not the antenna). The figures are, largely, for marketing purposes. Whatever you do, don't assume that an antenna with a higher gain figure measured in dBi works better than one with a lower gain figure.

Any gain figure measured in dB is always measured against something, because dB is a relative measurement, not an absolute one. Think about cars. How much does it tell you if I say my car will do 10mph more than a reference car without telling you what the reference car is? That reference car, if I don't specify it, might be an Aston Martin or a Golf trolley.

In the case of dBi, it's against a theoretical isotropic antenna. In other words, the gain has been calculated mathematically, not measured, because that perfect isotropic radiator doesn't exist.

And how well any replacement antenna works will depend on the exact radiation pattern and power levels compared to what you had before. The "doughnut" referred to by others is broadly right for a dipole, which (approximately speaking) is what you have with a traditional vertical antenna. But as soon as you start talking about the sort of directional antenna you mentioned in that link, you're talking about a very different radiation pattern from a doughnut. So any gain figure compared to a theoretical isotropic antenna is, in practical terms, pointless. It's useful for manufacturers though, because it gives them a nice impressive figure they can quote without actually having to measure how the antenna they build actually works. I have some nice antenna design software. I've built antennas designed by that software in accordance with the measurements. And it's hard enough to get two successive builds to perform identically to each other, let alone getting them to perform according to theoretical design criteria.

In general, many "high gain" antenna will work better than the type that come with cards. It might be that they're bigger, which can be an advantage but certainly isn't necessarily so, but it's also because you can move it around and if you put it up higher, you generally get a more efficient radiation, if only because the PC case isn't blocking much of the power (both transmitted and received). With a directional antenna, the benefit is typically even higher because the power sent in is radiated more specifically in the direction you want it to go. Broadly the same power goes in, but instead of radiating it in a circle, you sent it in a cone. But ..... the more directional that antenna is, the fussier it will be about being accurately pointed.

Also, directional antennas can work much better as receiving antennas because they're far more "selective" .... i.e. they're deaf to signals from most directions, meaning they can better hear signals from the direction they are listening in.



So the generic answer to you question is yes, high gain aerials work well. But it's provided you use the right type of aerial for your circumstances, and provided you use it correctly. As for which one works best, I'm afriad that in the absence of proper tests to determine whether an antenna is properly designed, and built, and using good quality materials, it's a case of either suck-it-and-see, or rely on anecdotal evidence. But unless the anecdotal evidence comes from people comparing it to the same original antenna as you're using, it's no guarantee you'll get as much benefit as they did. If your original antenna is good and theirs was rubbish, you won't see the performance benefit they did.

[jamin]

Another awesome post from Saracen. Thank you mate, your explanations are spot on.

[filbert]

wow thanks,
so do I go for the big aerial that matty-hodgson's got, this should make it better but it's still the doughnut signal @ £7
or somrthing like this that's the cone signal @£15

[matty-hodgson]

wow thanks,
so do I go for the big aerial that matty-hodgson's got, this should make it better but it's still the doughnut signal @ £7
or somrthing like this that's the cone signal @£15

well.. it all depends what you need
i only got the big 'doughtnut' aeriels because my dad uses his laptop a lot, i use my netbook, and PC so i couldn't have used a directional aeriel on the router otherwise i could've only pointed it at 1 device..

so, if you're gonna be stationary and never move the router/receiving device, the directional one will probably be better.

but for all round the router in several locations, the 'doughnut' 1 will be better.

[Saracen]

Matty has it just about right.

The "doughnut" pattern is ideal if you're moving a PC about the house. That panel antenna is directional, so it might be great if you're in the lounge (where it's pointed) but unable to connect at all if you're in your bedroom (or vice versa).

That's why directional antennas aren't ideal for routers unless you're doing some sort of bridge-mode connection, point to point .... say between your house and a mate's house 100m away.

The "dipole" isn't as strong either in transmitted power or the sensitivity and selectivity in reception, but it omnidirectional, so it works pretty well wherever you are in the house.

They're two different types of solution, for two different types of problem. Which one suits you depends on your situation.

[filbert]

So it's as I thought then, as my router doesn't have a replaceable aerial, a directional aerial for my pc would be best, I just have to try and pick one that works ok.

Thanks for your help.