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mini wifi antena - what to do ?

I got hold of a mini laptop in bad shape. I fixed everything except wifi. The situation is that right now i simply have 2 cut wires connected to wifi card, one is 4G and one is 5G wire. The laptop case is metal all around. I connected the 5G wire to some spare laptop mini antena and got 100Mbps when it was outside the case. As soon as i glued it to the case, went down to 8Mbps. I figured the only solution is to glue a mini antena to the outer side of the case, i got just enough space at the rear end of the laptop. In order for both antenas to fit, each would have to be no more than 1cm x 3cm (0.4 - 1.2 inch).

Since i never dealt with antenas of any kind before, what would be the best option to do this ? Should i order premade antenas or can i just make 1 from materials i have at home ?

I added some pictures. You can just spot where i put existing antenas, green on the bottom right (4G) and 5G on the left, sadly there is an LCD cable over it and screen case is metal, so blocking from all sides. Now i wanna put a new antenas in the middle. The default situation was both antenas were in this place at the bottom of the screen where you see the plastic is broken off. Its a chuwi laptop so i couldnt even find picture of the original antenas, let alone option to order them. All i know from pictures of built laptop that antenas leave the laptop case and go into this spot at the bottom of lcd.

Get antennas from scrap laptops. Most likely both connections are dual band, so get dual band antennas (2.4 GHz and 5 GHz).

What is the exact model of the laptop? Most likely there is a service manual or teardown video that will show where the antennas should be. There are types that are designed to work in close proximity to metal areas - many laptops have metal casings, with areas under plastic covers designed to allow the antennas to work.
There are many different designs of laptop WiFi antenna - these are just some I happen to had; another type I've used looks like just a fatter piece of heatshrink at the end of the cable.

You need to try and find a similar design to the originals, so the radiating element of the antenna is as close to the same position and orientation as the originals were.

And do not try to join the antenna cable, it is virtually impossible to do without significant discontinuity and signal loss. Just replace the whole antenna with cable, back to the connectors on the WiFi card.

Note that many laptops also have Bluetooth antennas, and some have WWAN (mobile phone data) so 3G or 4G phone frequencies, which are totally different radio frequencies / bands and different design to WiFi antennas.

(Bluetooth uses 2.4 GHz, same as WiFi).

I managed to find 2 mini antenas that are small enough that i will be able to put them somewhere outside the laptop without being visible. I have a couple of questions before i do that:

1) I took a photo of antenas, on second photo i put them side by side. They look similar. This is from a laptop that i think didnt have 5G support. Does it matter which of those 2 i use for non 5G and which for 5G ?

2) Both antenas have a silver duct tape that was used to glue this to the laptop screen case. This silver duct tape is connected to ground on antena and glued to silver foil covering the back of the screen. Basicaly its used to hold the antena in place but also to double as a connection to ground. Why is it done like that and can i remove this and just use antena since i need it to be as small as possible ?

3) Any other advices before i go solder my wifi wires to this new antenas ?

If an RF cable is fed to anything but a well-matched load (for the type of cable feed), the cable itself radiates - or picks up interference - and the antenna does not work well.

Adding a substantial ground connection (or capacitive ground, or counterpoise) to the antenna end of an unbalanced coax feed helps reduce that cable radiation, as long as the antenna is reasonable.

At RF, a conductor that is an odd number of quarter wavelengths long at the working frequency will not take any current if connected between signal and ground.

A badly mis-matched coax cable can do similar things, with the cable resonating and not passing much power to or from the antenna.

Transmission lines do not follow the same rules as normal wiring!
I managed to fix the thing to be reasonably OK. But some wierd things happened.

First i attached the antena to 2.4Ghz cable and put the antena behind the screen, surrounded by metal all around. To my surprise i got 60Mbps. Which is crazy because my 2.4Ghz in my apartment is pretty useless, the best case i got was like 20Mbps on my best devices. Then i attached the antena to 5G and stuck it near the 2.4Ghz antena thinking it must be a good spot. Then i tested 2.4Ghz again and blimey, i got like 1Mbps. Now, i dont know if i somehow managed to move the 2.4Ghz antena when pushing 5G near it or simply the fact that i connected antena to 5G cable did this but it was a big drop. I tried everything i could but never could get 2.4Ghz over 15Mbps again.

Spending probably hours moving them around, resoldering contacts, etc. Nothing solved it. In the end i just positioned the 2.4Ghz behind the monitor to get that 15Mbps and positioned 5G to the edge of laptop case where only plastic is and got like 60Mbps. So for now its gonna have to do.

For future i think it would be best if i just order a new antena. The problem is i have plenty of antenas at home but they use a big connector to attach to wifi card. This laptop uses a mini version of the connector. And searching places online like ebay, aliexpress ... there is no mention of the mini connector and from the picture itself its impossible to know if it is actualy the small or the big one. Also couldnt find any specs on the connector itself, like, does it have a special name, maybe dimensions or something ? Any help would be most welcome so i can order some antenas.
The connectors are either MHF4 or u.fl - the MHF4 are slightly smaller than u.fl

I believe generally the older style mini PCI & similar type cards use u.fl, the newer ones with a fine pitch edge connector similar to an M2 flash memory SSD use MHF4

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