Asus RT-AX88U 5Ghz antenna- internal or external.

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liukuohao

Occasional Visitor
Hi there,

Just want to ask the forum people, RT-AX88U 5Ghz band has 4 antennae, are they internal one or external?

I looked up at the internal photo from FCC site, but I cannot really work it out whether is internal/external

Or....whether it external but sharing the antenna with 2.4Ghz band.

Thank you.
 

Yota

Senior Member
Externally, RT-AX88U has only four external antennas, they support 2.4GHz, 5GHz and B/G/N/A/AC/AX at the same time.
 

liukuohao

Occasional Visitor
Externally, RT-AX88U has only four external antennas, they support 2.4GHz, 5GHz and B/G/N/A/AC/AX at the same time.
@Yota Thanks for your reply.

Can those antenna really operate 2 frequency bands at the same time? Apparently they can.

Those antennae are dual-band RP-SMA type (screw in type).
This means it can operate either 2.4Ghz OR 5Ghz.
If you unscrew RP-SMA type antenna, you see there is only 1 hole to couple with 1 male connector on the router.
This translates only 1 signal path to the radiating element buried inside the plastic.

I am not a RF engineer, just an hobbyist.
At this point I am still scratching my head, how can a router use an antenna to transmit 2 frequencies together.

Until, I researched further, because the Tp-link Archer C7 also implemented the same way: https://www.tp-link.com/us/home-networking/wifi-router/archer-c7/

2021-06-08_19-07-34.jpg


I dug up further from this Opewrt forum: https://forum.openwrt.org/t/archer-c7-1750-v5-antenna-modding/34930

Then bingo! I found my answer. The key word is: diplexer or RF diplexer chip

What is a diplexer? Watch youtube: https://www.youtube.com/results?search_query=diplexer
 

det721

Part of the Furniture
Many aspects of radio can use duel band even tri band in some cases. All work but like anything there is a trade off.
 

ColinTaylor

Part of the Furniture
@Yota Thanks for your reply.
Then bingo! I found my answer. The key word is: diplexer or RF diplexer chip
I think that would be a duplexer rather than a diplexer. Or more likely just-a-bunch-of-filters. Conveniently the 5 GHz band is approximately half the wavelength of the 2.4 GHz band so constructing a dual band antenna is simple.
 

liukuohao

Occasional Visitor
Many aspects of radio can use duel band even tri band in some cases. All work but like anything there is a trade off.
Do you mind sharing what is the trade off?

I am guessing, there will be a delay introduced due to the diplexer needs to switch back and forth
to pass 2.4GHz signal and later 5GHz signal.
 

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