I have bought a linksys EA8500. Flashed OpenWrt and so far I'm happy with it.
I'm now trying to optimize the wifi coverage and trying to get more information about the radio part.
This router is dual band (2.4Ghz and 5Ghz) and the instructions manual state that have 5 antennas (4 external and 1 internal - this one must be PCB-based). Anyway, I'm trying to understand if all the antenna ports are dual-band or if some are 2.4Ghz and others 5Ghz. I read somewhere that even though the physical antenna could be multi-mode, the port it attaches must be either 2.4GHz or 5GHz. I'm not sure it would be like that.
The TOH doesn't state it and does neither the linksys documentation...
Any thoughts on this?
This is one of those "If you have to ask, you shouldn't be..." questions.
Modification of antenna systems (or any part of the transmitter chain) for transmitters requires an appropriate technical license in most jurisdictions. Even with those licenses, modification of any part of the RF chain at 2.4 GHz and 5 GHz requires advanced knowledge of microwave circuit design and fabrication skills far beyond that which most computer hobbyists possess.
Yes, typically there are separate 2.4 GHz and 5 GHz RF chains, even if the antenna covers both bands.
Internal photos, such as those available through the FCC or those that make the FCC database more readable, such as https://fccid.io/Q87-EA8500/Internal-Photos/Internal-Phoos-2581256 can be helpful for guessing how the unit works.
Thanks for getting back!
This was the kind of info I was looking for.
My "radio optimization" is limited to choose how to place the antennas. The router is in the attic and the antennas are spreaded across it with sma cable extensions. Since I'm just using 2.4GHz a good starting point would be to know which antenna ports should I connect it. I'm not planning to modify the radio part or anything...
Unfortunately, by the photos and documents in that site, I'm not able to identify which ports are 2.4GHz and what are 5Ghz but I'll continue looking for it.
I'd check your signal levels with and without those extensions. You may be looking at a net loss.
High-quality, commercial cable, such as https://www.timesmicrowave.com/DataSheets/CableProducts/LMR-240-UF.pdf has a loss of ~0.5 dB per meter at around 2.5 GHz. If you're using "eBay" cables, you're potentially around 2 dB per meter, plus the losses from cheap connectors.
That's really not going to work well at all. Signals at these frequencies travel very poorly through any coaxial cable that would cost less than buying another AP for the other side of the house.
To answer the original question, the unit uses all four external antennas for both bands. The two radios each have four transmit-receive chains. One signal for each band is combined to each antenna.
It is not clear what the internal antenna does.