Yes. Antennas are designed for the specific range of frequencies that they are meant to be used with. Cellular modems in laptops, or any device, use antennas meant for cellular.
There are certainly extremely tiny usb wifi dongles, barely larger than the usb plug itself. But an antenna crammed into such a tiny space won’t work as well as a larger one. Hard to get around physics. So I’d buy one first and use it in all the places when you expect to use your laptop, comparing it tho the built-in wifi card. See if it’s really acceptable for you.
WiFi is at 2.4 GHz, 5 GHz, and 6 GHz, so the WiFi antenna is designed for roughly that range of frequencies.
Cellular signals have a much wider range of frequencies.
Mid-Band cellular signals (which are known for having a good balance between range and performance) typically operate between 1.7 GHz and 4 GHz (Mid-Band 5G tends to be towards the upper end of that range while Mid-Band 4G tends to be towards the lower end). Those are close enough in frequency to WiFi that they should work with antennas designed for WiFi.
Low-Band cellular signals (very long range with good object penetration) typically operate around 0.6-0.9 GHz. That is well outside the frequency range the WiFi antenna is designed for and is unlikely too work well (I expect it will work but get a much weaker signal than with an antenna designed for Low-Band).
High-Band mmWave cellular signals (incredibly fast, almost no range) operate above 24 GHz. That is high enough that I doubt it’ll work with a WiFi antenna.
mmWave would be useless for a laptop. Since you won’t get signal indoors. mmWave is stopped by almost anything.
It’s pretty useless for most people in phones, too. Coverage is just terrible due to physics at those frequencies. You need to be line-of-sight from a mmWave transmitter without even the slightest obstruction. And they don’t bother placing transmitters in most areas. Even your hand blocks the signal, need multiple antennas to even have a chance. But that costs more money and space, so not all phones have multiple antennas. They just want a checkmark on their spec sheet, doesn’t matter if it won’t work in actual use.
With the outdoor deployments that some carriers (mainly Verizon in the US, no one else has deployed at nearly that scale) have done I agree, however a lot of the potential for future mmWave uses is in convention centers and other buildings that tend to be packed with people.
Furthermore massive MIMO arrays and other improvements have gotten pretty decent at getting it to work through a wall (although much slower through that wall and often not through two walls).
Note that the oversized 4G expansion card that was being discussed some time ago reportedly has working (and shipped) prototypes and is now on preorder for about 170 GBP:
(It only supports 4G, and looking at prices for 5G modules it doesn’t look like this is going to change any time soon—even 4G modules are 60+ USD in small quantities, and 5G ones are several times that.)
yeah, I have seen the 4g oversized modem, but I wouldn’t want it to stick out of the chassis and thinking that 4g/5g may even be decent enough to be the primary connectivity in my parts of the world and if not a usb dongle that’s always plugged in (less obtrusive) might just be good enough.
When buying a laptop with LTE-modem and antennas preinstalled, what kind of antennas are they using? Is it the same “wire-like” antennas like they are used for WiFi? Would it be possible to fit 2 of these inside FW laptop?
Or do all 4G/5G antennas have such a thick module at the end like this one sold on ebay?
Thank you Sir! That explains a lot to me. I didn’t know yet that WLAN antennas have this kind of antenna module at the end too. I always thought the WLAN antenna is just a wire - in contrast to antennas inside an access point.
It might be confusing because some antennas are simply a piece of wire. AM/FM radio is a good example of this. How well that works depends on the frequency and strength of the signal. Cellular and wifi normally use more sophisticated antennas.