Are wireless antennas generic?

[Maximilian]

Like do they all support 2.4 and 5 ghz? How about wireless standards like n/ac/ax? I have noticed the RP-SMA and SMA standards, it just seems to determine the connectors on the antenna. Am I right in thinking these are just hunks of metal encased in plastic and a wireless g antenna plugged into a wireless ac router would work okay? Im not going to do that im just curious.

 

[mrc]

I'm no expert on the subject.....

Do a degree, there is not large differences I will assume - of course, there are some very different fundamental designs (omni vs. directional, how much gain, dipole vs monopole etc. For directional antennas, the designs are quite different. ). I would _guess_ that you to a degree can get the same performance with many antennas, but to get the optimal performance, that there are differences. Lets say that a optimized antenna/antenna design can make a 15% difference.
An omni-antenna can to a degree also be directional - in what direction should the power of the signal to - equally distributed?

For e.g. a MU-MIMO-router with four antennas - based on the shape of the antennas on my of these routers, are they "focused" in different directions?

For 2,4 and 5 GHz. From what I understand, antennas are designed to work, and that you can get quite poor results on some antennas. I seems to remember earlier that there was quite a few routers with dedicated anteannas for 2,4 and 5 GHz. E.g. for 2,4 GHz internal antennas was used, while 5 GHz used the external antennas. Based on the limitations in the regulations for use of 2,4, there is from what I understand normally quite limited extra performance from external antennas on a modern design - this based on the power- and gain-limitations.

Fro manufactureres of wifi-equipment, there can be a quite a lof of optimalization of the antennadesign based on rest of the router. External antennas can in this way be easier, but provide extra cost during manufacturing - a "normal people" want a router that "looks good".

 

[dosborne]

Just from the reading I have done (I have no direct experience) there can be quite a difference between antennas and that is why you see so many for sale on ebay and other places. They typically have different (and supposedly better) db ratings. However, I've read too many stories about mismatching the antenna for the radio hardware that makes things worse, and potentially to the point of burning out components. The size, shape, db rating, connectors and quality can all influence the strength of your signal and the coverage area, not always for the better.

In general, I believe the answer is that the manufacturer included appropriate antenna for the circuitry in the device (router) that you purchased and unless you really know what you are doing, and have equipment to measure any advantages, you are best to leave things as is.

 

[sfx2000]

Like do they all support 2.4 and 5 ghz? How about wireless standards like n/ac/ax? I have noticed the RP-SMA and SMA standards, it just seems to determine the connectors on the antenna. Am I right in thinking these are just hunks of metal encased in plastic and a wireless g antenna plugged into a wireless ac router would work okay? Im not going to do that im just curious.

The better OEM's do match the factory antennas to the radio circuitry on the board, and there's the factory calibration to back that up.

I can't speak much for Broadcom, but Atheros does have the factory calibration tool - the Atheros Radio Test, and the calibration files are stored in a partition in the filesystem named, appropriately enough, .ART

I generally recommend to keep the factory antennas, and avoid the third party ones that are offered on places like eBay and Amazon, as most vendors there do not have the capability or tools to actually prove the performance - most just repackage stuff from Alibaba or other outfits in China, and sell them at a fairly high profit.

 

[Maximilian]

Well just to report back I used some antennas from aliexpress (reputed to be the same ones Asus uses on some of it's routers). They seem to work fine so no issues.

 

[sfx2000]

I'm no expert on the subject.....

Do a degree, there is not large differences I will assume - of course, there are some very different fundamental designs (omni vs. directional, how much gain, dipole vs monopole etc. For directional antennas, the designs are quite different. ). I would _guess_ that you to a degree can get the same performance with many antennas, but to get the optimal performance, that there are differences. Lets say that a optimized antenna/antenna design can make a 15% difference.
An omni-antenna can to a degree also be directional - in what direction should the power of the signal to - equally distributed?

With MIMO, the antenna array works together - so they should be matched... each antenna is transmitting part of the symbol stream that is generated by the Baseband to each Radio.

For e.g. a MU-MIMO-router with four antennas - based on the shape of the antennas on my of these routers, are they "focused" in different directions?

Generally not - the antennas are just radio emitters - the size and shape aren't really material here - what is significant is the gain of the antenna, as this impacts the pattern - low gain is like a sphere, as you go higher in gain, the sphere flattens...

Beamforming for 11ac (and MU-MIMO) is a function of time diversity - there's a slight delay from one antenna to another in the array, and this steers the beam on the downlink. There is no beamforming on the uplink from the client, but the AP does do receive diversity on that side, and combines the symbols received at the baseband.

For 2,4 and 5 GHz. From what I understand, antennas are designed to work, and that you can get quite poor results on some antennas. I seems to remember earlier that there was quite a few routers with dedicated anteannas for 2,4 and 5 GHz. E.g. for 2,4 GHz internal antennas was used, while 5 GHz used the external antennas. Based on the limitations in the regulations for use of 2,4, there is from what I understand normally quite limited extra performance from external antennas on a modern design - this based on the power- and gain-limitations.

A well designed AP - the RF engineer is going to match the antennas to the design spec, and there, one can play with gain of the antennas, along with proper choice of the PA's for downlink, and LNA's for the uplink - and a dual band antenna for WiFi isn't that hard - just different matches on the front end to load the antenna appropriately.

Fro manufactureres of wifi-equipment, there can be a quite a lof of optimalization of the antennadesign based on rest of the router. External antennas can in this way be easier, but provide extra cost during manufacturing - a "normal people" want a router that "looks good".

That's a valid point - and this goes back to product marketing and business development, where the design ID is set for the market the OEM is attempting to address... A good RF engineer can do an equally good job with external antennas or internal antennas - I prefer internals myself, as that always allows for proper placement for an optimal RF design.