With more antenna gain, the power needs to be reduced. Be aware that, to remain legal, if you use a 10dB antenna then you must reduce the transmit power by 10dB. Hence the received power will be unchanged. OTOH, you can use a high gain antenna on the receiver without restriction; this reduces the interference you suffer due to other transmitters.
The key point is that the transmit power is defined as EIRP effective isotropic radiated power , i. The reason is that the power limits are defined to contain the chance of interfering with other users.
There is no transmitter and receiver in wifi. All cards are both transmitter and receiver, so you could not only use a receiver antenna. I think you missed the point that Wireless LAN is not unidirectional.
While it is a half-duplex technology, there are no receivers and transmitters. If you use a high gain antenna on either end, it will not only boost the received signal, but the transmitted one aswell.
I entirely understand that, having been involved in and using WLANs since before WiFi emissions rules vary by country. Are you referencing the rules of some other country? A number of very much type-approved directional antennas frequently used in commercial WiFi in the USA disagree with your statement as it is written….
The rule is your EIRP cannot go over a certain amount. To assume that you cannot to any degree focus the energy in one direction more than the stock antenna already did is to assume that the EIRP of the router with the stock antenna was already sitting right at maximum. Please understand dB by itself means bugger all. It needs to be compared to something so we get an absolute value. And this is why dB is an insane system of units. Who ever thought that was a good idea?
In EU the limits of use for 2. Find the wlan adaptor with the highest receive sensitivity dBm dBm. Connect the SMA Male end of the cable into the back of the router securely. Leave the other small antenna connected into the back of the router. Connect the F Male end of the cable to the Yagi Antenna. A Yagi antenna is used for communications in a medium range of three to five miles between two points. It can also be used as a bridge antenna to connect clients to an access point.
This term is also known as a Yagi-Uda array or patch antenna. A lot of electronic devices and appliances use the 2. You have to trim the paper clips with a nibbler or plier to fit the vertical bars "elements". This is fairly straight forward. Lay the paper clip on the template's element and mark the ends with a marker.
Snip at the marking. Make sure that each element fits correctly the length of the bar on the diagram. Fix the elements in place with crazy glue. Leave element 2 for later. This is the element that connects to the electronics and is called "the driven element" as in being driven by electronics.
The backbone holds the shape of the antenna. I just cut pieces of popsicle sticks and fit them between the gaps of the elements. I used white glue to fix them in place. Start from element 15 backward.
When you arrive to element 2 move on to the next step. The "driven element" in a Yagi antenna, is usually the second one from the start.
It is a broken loop and not a straight wire. A loop of wire resonates at a specific radio frequency depending on its dimensions. The dimensions of the driven element in this antenna is set at 2.
It just happens that its about the size of a common big paper clip. You need to clip the paperclip so that it loops around and meet in the center but the end not touching, leaving a gap see photo. Fix it in place with crazy glue and build the back bone around it. When all the elements and sticks are in place, reinforce the antenna with another layer of popsicle sticks. Glue full lengthed popsicle sticks on top of the antenna. The antenna should become mechanically stiff. Then rip the paper template of the antenna.
This is the most difficult part and depends on the electronic hardware you have. The basic idea is that you need to solder a wire between the WiFi board's RF output and the driven element of the yagi antenna. Those with external antennae, like mine, are easier to connect because you are just replacing the external whip antenna with the Yagi.
Those with internal antenna may need to have their on-board strip antenna modified as illustrated in the pictures here. You need to slightly experiment in this case.
I have tried soldering a coax to my board's antenna connectors and the two ends of the yagi's active element loop but it did not work in my case. I have no explanations why that did not work, but other DIYers that have built Yagi antennae connected their antenna in this manner. In my case, I just connected a single thin strand of copper wire between the active element of the strip antenna and one end of the loop of the driven element.
Please read the annotations of the pictures for more details. The performance was pretty spectacular for this easy to build antenna. I was able to see the WiFi of a hotel that was 2 miles away from my home. The most difficult part was connecting the antenna to the USB modem. Okay well I read through the entire post and I saw many things that made a lot of sense, also saw a lot of unnecessary flaming, but I do have a few comments to make.
Right off the bat the one individual that asked about having his modem in the basement with a rotating antenna on the roof needs a reality check. Take the dongle apart and connect a USB extension cable to it and mount it directly on the antenna assembly.
Paper clips vs copper, at this frequency it's not going to make much difference, however the specific model was generated using 14awg copper. Someone said glue it all to cardboard then cover it with more cardboard actually a strong and stable design, original author said build around popsicle sticks wooden , both are subject to absorbing moisture from the air and either can have a poor dielectric constant, I would suggest some kind of plastic they make popsicles with plastic sticks.
The lengths of the elements, the spacing between them, and keeping them all in the same plane and parallel to each other is the most important consideration.
Just remember, the general idea is to reduce the amount of loss and retain as much gain as possible. Antenna Gain and Cable Loss are values that are constant no matter what power level you are referring to. The referenced unit is exactly one milliwatt. Since it uses a reference point of exactly one milliwatt, it is an absolute unit of measure. The conversion of watts to dBm uses a complex formula that goes beyond the scope of this section. In short, 1 watt or mW is equal to 30dBm. If you have cable loss of 2 dBi based on your cable length and diameter , but a gain of 7.
With outdoor applications and runs over 4 feet long, use low-loss cable such as: LMR If you have a 20 foot run, use 19 feet of LMR for the main line and the smaller LMR cable for a 1 foot pigtail equipped with the connectors you need.
If you mount an antenna outdoors, make sure you use a lightning arrestor. Lightning arrestors protect the router or access point from electric surges from lightning strikes on or near the antenna. Gas charged lightning arrestors offer excellent protection.
They respond to electrical surges by safely dumping excessive voltage to the ground. Therefore, they must be grounded properly in order to work! This little guy can save your Wi-Fi radio from getting fried. Drive a solid copper rod 4 feet or longer into the ground. Run a solid copper wire 8 AWG or larger from the lightning arrestor to the grounding rod.
Secure the ground wire to the copper rod with a with a grounding strap.
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