Hi
Are that Ports use for Wifi or LTE?


And what does the 2 Square Black thinks next to the Antenna Ports?
Thanks

No idea?

Reading the manual would help:
https://help.mikrotik.com/docs/spaces/U ... u+LTE18+ax
the hint is here.

Antenna usage

SMA connectors are for LTE antennas.

External antenna sockets are located on the back of the device. Device comes with connected wireless antennas, LTE antennas are not provided within the package.

I would say they are for LTE antennas

Looking at this open router, it looks like the two ports are connected to some PCB traces that connect to a horizontally and a vertically oriented antenna inside the enclosure.
**update** I deleted the photo to avoid confusion for future readers. See posts below.

I am wondering if it makes any difference if I connect an external antenna to ANT2 or ANT3. My guess is that it doesn't matter. But in theory an external antenna on a long cable could introduce multipath noise, as signal from the external antenna will arrive at a different time than the built-in antenna.

I am not understanding.

The photo you posted is of another device, RBD53G-5HacD2HnD is the Chateau LTE12, the LTE18 AX should be S53UG+5HaxD2HaxD.
The image, coming from this site:
https://mikrotikon.pl/mikrotik-chateau- ... uteros-v7/
is even called MikroTik-Caterau-12.jpg

guilty as charged. I assumed the wiring was the same

No, they are different.
JFYI, on this forum:
https://confusedbird.com/thread-280.html
there is a link to a google drive with some photos of the internals of the LTE18:
https://drive.google.com/drive/folders/ ... drive_link

When connecting an external LTE antenna to Chateau LTE18 ax, does it make a difference if I connect it to ANT2 or ANT3? Don't know the meaning of "primary/diversity" as they talk about on confusedbird.com
High gain on ANT2/primary sounds like more-better

With MIMO radio systems (WiFi from N onwards, mobile broadband from 4G/LTE onwards) the distinction between "main" antenna and "aux"/"diversity" antenna doesn't exist any more. All antennas are equally important. Some chipsets/drivers simply hate it when signal levels, received from different antennas, are too much different. If only one antenna is improved, MIMO doesn't work and net effect is not very positive if positive at all ... some chipsets/drivers become unstable and connection becomes intermittent.
So when "improving" antennas it's important to do it properly for all Tx and Rx paths.

So it would be a bad thing to plop an antenna like this on my roof, attach it to ANT2 and call it a day?
https://www.pctel.com/antenna-product/w ... ering-sma/
Because the receiver hardware expects a certain signal from the built-in antennas?

So it would be a bad thing to plop an antenna like this on my roof, attach it to ANT2 and call it a day?
https://www.pctel.com/antenna-product/w ... ering-sma/
Because the receiver hardware expects a certain signal from the built-in antennas?

You can use an external MIMO antenna.
Example:
https://www.wimo.com/en/lte-5g-diretional-antenna?