I'm especially wondering about wifi aplifiers (2.4GHz and 5GHz).
I have a couple of very basic questions about them. (I hope this is not too much for a single question):

  • Are there special signal amplifiers for routers and for client machines or would the same amplifier work on both? (I'm wondering because this one says "don't connect with network card".)
  • Does a signal amplifier work in both directions (upload and download) even if only one of the two parities is using such a device? (The one linked above says "bi-directional", has this anything to do with this?)
  • If it would actually work for both (sending data and receiving data): how does this work? I get that you can use an amplifier to make your sending signals stronger, but are the amplifiers also be able to better pick up weak signals?

(I am well aware of the strict laws related to transmit power limits etc.)

  • \$\begingroup\$ Short answer: NO, amplifiers work in only one direction. The module from your link is unsuitable for people like you who have no clue about how transceivers work. If you want to learn about RF and transceivers, good for you, start reading some books about it. If you just want to increase your Wifi range (that's what I suspect) you will FAIL if you try to do that with a booster. Get a Wifi repeater or an extra access point. Those work and are 100% legal. \$\endgroup\$ Mar 10 '16 at 10:00
  • \$\begingroup\$ You don't have to know how they work to use them properly. ;) There is certainly no need to read a book about it. Some minutes of research on the Internet will do. That being said, using a signal amplifyer for 2.4GHz is not illegal in my country as long as you leave the transmitting power under a certain limit. And yes I have all the equipment to measure that out. \$\endgroup\$
    – Forivin
    Mar 10 '16 at 14:56
  • \$\begingroup\$ If you know everything already or it can be found on the internet, why are you asking a question here then ? Why are you asking if an amplifier is bidirectional when you later say that you don't need to know that in order to use it ? Obviously you do not want to understand how things work so why are you asking ? \$\endgroup\$ Mar 10 '16 at 15:06
  • \$\begingroup\$ @FakeMoustache I'm totally onboard with your comments. As a matter of interest perhaps, I have a full duplex transceiver made of Esaki diodes. I'm sure there's a few other esoteric exceptions. There's currently the nZero work through DARPA that might come out with some full duplex amplifiers. Now that we can get a circulator on an IC, we probably will see more things that "appear" to be full duplex. The SPAR BAA work is duplex front ends. Just some random trivia to displace other random trivia. \$\endgroup\$
    – b degnan
    Mar 10 '16 at 15:17
  • \$\begingroup\$ @FakeMoustache Wow what is wrong with you. Calm down, alright? Neither have I ever claimed to "know everything", nor have I claimed that "everything can be found on the Internet". I'm simply asking how something works and I could not find helpful information about it. I basically already know how to use it and I know there are tutorials online that show how you can safely use such an amplifier to improve your wifi experience without affecting others. Being able to use something doesn't mean you have to have read books about how it works... Knowing how to use it is simply not the same thing. \$\endgroup\$
    – Forivin
    Mar 10 '16 at 17:29
  1. No. They are the same. Likely they don't want you to use a USB network adapter for other design reasons (like how most of them don't have the RF link that you need to attach to this board, they instead have internal antenna and their own compensation networks).
  2. Yes. Technically speaking an RF amplifier only works in one direction. This board likely either uses two amplifiers which are time division multiplexed or has only one amplifier and a time division multiplex back to the receiver without any amplification. (If they are fancy and thoughtful, they might even be using an active isolator).
  3. As I described above, the incoming signal is routed to a different amplifier, "facing" the other way. This way neither amplifier can drive the other (amplifiers go poof), nor can the other amplifier use the antenna at that time (no garbled signals from talking and listening at the same time on an antenna that might not be perfect).

This is all very abstract and high level of explanation and the exact details aren't perfect. It's not my design. I've never seen this before in my life. I don't generally trust Chinese designs unless they release a parts list. The board is also missing its RF connectors, which makes me dislike it even more. (Honestly, it's a bit shady to have an RF board without any RF connectors. Like I can literally see the solder points but they are so obviously designed for a side mount standard coaxial screw that I wonder why they're not there.)

  • \$\begingroup\$ I'd say the connectors are missing to make this thing as cheap as possible. I actually prefer it this way because depending on the case you will use for it you would chose different connectors. Like 90° angled ones or some with screws on, or female on the one side and male on the other side... Or maybe instead of RP-SMA you want U.FL... \$\endgroup\$
    – Forivin
    Mar 10 '16 at 14:49
  • \$\begingroup\$ But back to the topic. So it is really possible to pick up a signal that is so weak that other wifi adapters don't even see it and amplify it so that it is usable again? Wouldn't this introduce some kind of unwanted "noise"? Like a microphone would if you tried to pick up someone speaking a mile away from you? \$\endgroup\$
    – Forivin
    Mar 10 '16 at 14:52
  • 2
    \$\begingroup\$ @Forivin be aware that 4 W of WiFi is most likely illegal in most jurisdictions. While the board might very well boost the uplink range, it will do little to the downlink. Yes, it does have a 10 dB downlink amplifier as well, but if the downlink signal is already swamped in noise you will amplify the noise as well leading to little improvement. Other devices will receive data more reliably, but your end won't unless you stick these to both ends. I'd suggest ditching these and getting repeaters. \$\endgroup\$
    – jms
    Mar 10 '16 at 15:09
  • \$\begingroup\$ @Forivin, There are techniques to reduce noise like spectrum windowing and other things, but yes, eventually you will run out of signal to noise head room and have your signal lost in the noise. But, just as jms says, these are likely highly illegal in your local area (Pretty sure I can say the entirety of the USA and Canada and European Union) plus it's only really of benefit if both ends have this type of amplification board unless you only care about unidirectional communication. \$\endgroup\$
    – Dave
    Mar 11 '16 at 2:45
  • \$\begingroup\$ @Forivin, You couldn't use u.fl on this board. Like I said, those solder points are made for only threaded type connectors that mount at a 90 degree angle. u.fl wouldn't be able to attach to that solder point. So if you really want a female on one side and a male on the other I guess this could be helpful, but most of the time it's easier to get a cable that does the conversion than to take the time to solder a different contact. \$\endgroup\$
    – Dave
    Mar 11 '16 at 2:51

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