wifi antenna question

[cashkennedy]

So I bought a few Lenovo M73 tiny PC's (book sized / nuc sized). If you get a wifi / Bluetooth card installed it comes with a rear antenna (standard 0-90 degree angle plastic antenna) and an internal antenna. You need 2 antennas supposedly to concurrently use Bluetooth and wifi. The front antenna is behind a 2 sided plastic screen on the front bezel. (To allow the radio waves to enter the case / reach the antenna)

http://shop.lenovo.com/us/en/desktop...ries-tiny/m73/

Anyways, no one sells the exact antenna alone. So I was considering generic options on ebay for a roughly 1.5" wifi antenna, but then I took appart the Lenovo one to determine why it was 3d, and it has 3 cubes in the front made of plastic I assume, and possibly has the metal traces on 3 sides of the cube? Any one seen this design before? Is it vastly superior to if I just stuck a 1 sided antenna in the space?

[ratdude747]

Re: wifi antenna question

It depends on a lot of things. You see (I have a BS in EET), electromagnetics (the field which antenna/RF design fall in) is a very complex science and art.

Since the connectors are the same, the impedance of the antennas is the same, so yes, you can switch them (if not, there would be bad issues, ranging from poor/no connectivy in the best, a fried radio in the worst)... but for wifi antennas this has been standardized for years (50 ohm IIRC, like most RF/lab equipment).

What's different is the radiation pattern. In general, asemetrical antennas have asymetrical patters (that is, it's directionalized). This is done, at least in laptops, in order to deal with physical constraints. In this case, it's probably space (as always), but also the fact that in order to meet EMI specs (yay FCC), there is a conductive chassis, which also blocks RF such as the Wifi signal one wishes to be able to receive and transmit efficiently. Hence, by making the antenna more directional in the direction that the chassis is in, the effects of the chassis can be cancelled out.

Whether that is the case I can't say... radiation patterns are, to put it lightly, a real bastard to calculate (lots of heavy calculus and the like for an arbitrary non-standard design) and w/o lab equipment (spectrum Analyzer and RF generator) impossible to find empirically.

Either way, I'd stick with the stock antenna unless there is an issue, in which case then I'd try switching. RF is tricky stuff (especially at 2.4/5GHz !); the engineers that designed stuff know what they're doing.

[cashkennedy]

Re: wifi antenna question

I definitely plan to keep the stock antenna on the one that I bought that came with it, but the questions is what can I buy/ build for ones that didn't come with the antennas.

[cashkennedy]

Re: wifi antenna question

I was considering getting http://www.ebay.com/itm/2-x-IPEX-MHF...item3aac356f90

because it looks to be approximately the 4cm or so that the rf hole is large, and comes insulated already and has around the right cable length (7 inches).