Explain wireless Antenna + dBm to me

tigerstyle · 2 Mar 2012 at 13:39

So I have to use wireless sometimes, hotels and such, so wanted to ensure I didn't have some of the problems I had last time. I downloaded 'tweaked' drivers for my onboard Atheros wifi chipset that allowed me to adjust a few settings to hopefully make the connection a bit more stable, and they worked kind of, but wanted to nail patchy hotel wifi once and for all.

So bought this pack:

No my preferred brand or even choice of kit but limited as to what can be had here (South Korea hence the funny writing on my keyboard)

The USB dongle uses an 'RALink' chipset, had to download drivers from their website to get it working and it's running fine now. But really wanted the '4dbi' version of the same a bigger antenna has to be better right?

Good news is compared to the 2 networks my onboard Atheros finds this IPTime pulls up 15! And has shown 21 when I pointed it out of the window here! But I saw less networks when using the 2.5dbi antenna even if I waived it around in any direction. The 2.5dbi antenna might be useful for trailing out of windows or just for the 1.5M long cable it has but I thought the lower the dbi antenna the better? How does it work?

Now I have to see if it supports packet injection, but thats different...

Duke · 2 Mar 2012 at 14:05

Nope, the higher dbi the better.

tigerstyle · 2 Mar 2012 at 14:20

Duke said:
Nope, the higher dbi the better.

Thre must be a time where lower is better, as seen below in inSSIDer, is it the higher dBi gain on the antenna is a plus, but, but, but meh I don't know?

Back of the box for the usb adapter translates as: Transmission Power 16dBm +/- 2dB

firstborn · 3 Mar 2012 at 01:20

Duke said:
Nope, the higher dbi the better.

Care to expand?

Duke · 3 Mar 2012 at 10:30

firstborn said:
Care to expand?

I don't know much else, just from experience the higher dbi the antenna, the better the signal will be - whether on the receiving side like a pc/laptop or on the router/access point side. It depends what you're doing though, i.e. point to point with a lower dbi direction antenna would be better than a higher dbi omnidirectional one, as most of the signal would be wasted as such.

pyropetepete · 3 Mar 2012 at 11:35

dbi is the strength of the antena signla thats kicked out! The higher the better.

Duke doesn't matter if omni or directional.

wonko · 3 Mar 2012 at 13:16

Not sure if this will help or just confuse, but dBi is a measure of an antenna's gain relative to a theoretical isotropic antenna (one which radiates equally in all directions). It's a combination of the directionality and efficiency, so generally a higher dBi means greater directionality.

PistolPete · 3 Mar 2012 at 20:03

tigerstyle said:
Thre must be a time where lower is better, as seen below in inSSIDer

You are misreading the figures as they are negative. Higher is better but that is denoted by a lower loss.

wonko · 3 Mar 2012 at 20:10

Those values are probably the received power level in dBm. A less negative number will mean a greater received signal (i.e. -81 will be a stronger signal than -85).