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I already have a directional wi-fi 2.4 antenna with a gain of about 25 dbi. I also have an adapter, however, the power of the receiver/transmitter is not enough. My apartment is on the 9th floor, besides the land plot is not close. There are tall trees. Therefore, the signal strength is clearly not enough. I could buy a parabolic receiver with a built-in amplifier, but it's very expensive, and besides, I already have a Yagi antenna. I believe that such an amplifier should have SMA or RP-SMA connectors.

Are there such Wi-Fi signal amplifiers that are placed between the adapter and the antenna, and amplify both for reception and transmission?

What is the correct name for these amplifiers? (for search)

UPD 1: Both the antenna and the adapter have an impedance of 50 ohms. At least that's what the manufacturers say. I didn’t measure it myself, because I didn’t have the necessary equipment. However, as far as I understand, most routers and wi-fi adapters work with antennas with an impedance of 50 ohms. The coaxial cable also has a characteristic impedance of 50 ohms.

UPD 2: Installing Wi-Fi repeaters is an almost impossible task, since for this I need to install repeaters in both the house and on poles along the street. I hope to still benefit from a directional antenna with an amplifier. My problem may be the tall trees nearby, but the amplifier should help fix that.

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  • \$\begingroup\$ Generally using amps on wifi is illegal in most jurisdictions. Have you considered the cable loss? At a distance you want to be using CNT400 or maybe heliax. Or maybe you have the electronics close to the antenna in which case there’s not an opportunity there. As for what the amps are called, i’d search for wifi amplifier or booster. Maybe add masthead. \$\endgroup\$
    – Kartman
    Commented Jul 19, 2021 at 23:21
  • \$\begingroup\$ @Kartman I did not take into account the losses in the cable. The cable is 1.5 meters long, 50 ohms. As far as I understood, my adapter has a base power of 19 dbm, which is not enough. amplifer, booster, masthead - all this leads me to ready-made installations, or to LTE. These installations are expensive, and they are not needed. I only need an amplifier. \$\endgroup\$
    – Alex A.
    Commented Jul 20, 2021 at 0:22

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To answer your question from purely an RF perspective, yes, such items exist. You would need a bi-directional amplifier with an operating range in the 2.4 GHz band, as well as low pass filters on the transmit side to handle any higher order effects.

However, this amplifier would need to have the same input/output impedance to ensure that the SWR was low and therefore most of the power (S21) is getting to the amplifier and then to the antenna. With this in mind, as @Kartman suggested, have you looked into the input impedance of the WiFi antenna? If the antenna is made for, say 75 ohms, and the WiFi AP is expecting 50 ohms, then a serious amount of loss is going to be occurring. If you have something like a VNA, you can measure this to be sure that both the AP and antenna match, as well as look at how lossy the coax is if it is separate. Also, if you are on the 9th floor, is the antenna outside (such as on a deck?) This can make a huge difference based on the attenuation of things like concrete, steel, or brick.

As for the legal implications, in the US at least, the FCC limits everything you do RF. It is their job. For the US, the maximum RF output power is 30dBm or 1 watt. Some WiFi APs have this as an option, so it could be possible that to save power for normal applications the AP only runs at 1/2 the possible power. You could check the settings for your manufacture to see.

Finally, from a distributed systems prospective, WiFi tends to be expanded by WiFi repeaters or via cabled connections. The repeater option is slow but cheap, as it introduces latency for each hop back to the main, and can cause other issues if the mesh becomes large (see Aloha Protocol for more details.) The best way to do this is to have an AP at least on each floor of a building, and bring all of those back to a switch and manage them with a common controller (think DHCP, DNS, etc. being consistent so you can move through the building.)

Your configuration was not explained well, so I am not sure if the building is the provider or ISP or something else. If you could maybe explain this better it would help with options, as well as your country of origin to look into maximum power restrictions.

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  • \$\begingroup\$ I have clarified the data in the question a little. As for my country, yes, I am from Russia. And I know about the limit of about 20 dbm, but I would not like to refer to the laws (20 dbm isn't enought). Still, I will not use the installation for permanent work. On my plot of land, 3G is caught, sometimes LTE - they are enough for most of the works. But when I need to download 40 gigabytes (for example), I either have to go home or not download, because it is long and expensive. \$\endgroup\$
    – Alex A.
    Commented Jul 20, 2021 at 1:18

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