What's in a WiFi antenna?

Bendy_House

The usual short - around 4" - ones that you get with WiFi cards and stuff, with the folding end and SMA connector.

Trying to boost the signal from a WiFi camera, and used an SMA extension cable to try and get the antenna closer to the router, but this fails dramatically - a much worse signal. I even have the antenna right up against the router with a 5m ext cable, and it's only around a 38% signal! What the?!

Problem is, these aerials have been bought separately, as have the cables, so I don't know which of them to 'blame'.

If I can replicate what's inside an antenna, then I could use this to compare it with the 'real thing'.

Cheers.

FreeBear

What is actually inside an antenna - Just a short length of wire cut to a specific length to suit the frequency being used. Make sure you are using the correct antenna for the wifi frequency - i.e. 2.4GHz or 5GHz.

Bendy_House

Thanks FB. I think the antennae used for these two frequencies are the same, presumably why one is virtually twice t'other?

I think they have 'spirals' in them too, but no idea what they perform.

Mutton_Geoff

Bendy_House said:

I think they have 'spirals' in them too, but no idea what they perform.

It's part of the design to shorten the length of the aerial. They are called helical antennas.

FreeBear

Bendy_House said: Thanks FreeBear. I think the antennae used for these two frequencies are the same, presumably why one is virtually twice t'other?

The length of an antenna needs to be carefully calculated in order to operate at maximum efficiency. For a full wave antenna operating in the 2.4GHz band, the length should be 114-119mm and in the 5GHz band, a length of 49-50mm is needed. To save on materials, a half length or quarter length will suffice.. So a quarter length antenna for the 2.4GHz band would be a (nominal) half length in the 5GHz band. But for a number of reasons (the actual frequencies being used), a dual band antenna has to be a compromise - This in turn, affects the efficiency and can make a huge difference to the range.

If you know precisely what frequency you are using, and want the best performance, you'd be better off making your own antenna. Alternatively, purchase a quality antenna designed specifically for the band you want to use (so no cheap ebay purchases).

ic

Sounds like you need to upgrade your wifi network.  Amazon are doing a good deal on Google Wifi right now, since upgrading to that a few years ago I now get fantastic speeds throughout my house and garden.