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guest9999

Problems with 21 dbi antenna

Posted (edited)

Hi guys!

I don't know what is wrong, could some of who are experts take some time and give me some info.

I have Alfa NHA usb adapter.

When I use Alfa directional 7dBi antenna(which is pretty small) as seen in photos I have ok range, works nicely, solved driver issues.

I want more range, seems awesome to get more range and I bought 21 Dbi panel antenna(pretty large), 2.4 Hz range as in photos.

The thing is I expected that there will be a lot of increase in range and was all excited. The thing is the range from the 21 dBi polish made yagi.pl panel antenna is in similar range as in smaller 7 dbi one, it works even worse I think. I don't get it. The coaxical cable is 3m long, the connectors were made by a guy who does that often. I don't understand why is the range so bad, is the design from polish antenna for 20-40 euros bad, or is the cable issue or am I expecting too much, do I need to calibrate it somewhow?

The big 21 dBi antenna on the photos is 40cm x 40 cm.

I hope someone will take some time to answer, I don't understand it.

Thank you!

 

 

 

20220408_213648 - Copy.jpg

20220408_213708 - Copy.jpg

Edited by guest9999

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,,, try to open the antenna panel, there may be something wrong inside or check the coaxial cable and the connections with the sma plugs...!!!

... could you show the inside of the antenna ... ??? !!!

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Hi!

Here are the images.

I tested the cable with multimeter, resistance is same, 0,5 for outer - outer part or inner - inner part seems good if I as amateur understand it.

When I tested connected cable with antenna - outer part resistance readings seem good, but inner ones are out of normal as in images(exchange between 0 and 191.8). The connection between large connector on coaxical cable(inner part) and antenna could be the issue. I don't know.

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CIMG2696 - Copy.JPG

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CIMG2701 - Copy.JPG

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I also need these dimensions ... !!!

screenshot_1188.jpg

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Posted (edited)

It is not super precise or always symmetric -1 mm error in some instances. Rectangles are 61 x 45 and not 60 x 45. Also backplate reflector is 410 mm.

antenna_inner1 - Copy.jpg

Edited by guest9999
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,,, this antenna is one of the best, I wonder why it doesn't work for you...!!!!???

screenshot_1194.jpg

,,,, with 2x2 such antennas I don't think it has a gain of 21dBi but only 18 dBi....

screenshot_1195.jpg

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Admin thx for the effort. At least I know the antenna is good. I don't understand that as well, I don't get it. I will buy adapter and try alfa nha directly on the antenna without the cable. I will buy one 12 dbi one as well and compare the results. I expected that that antenna would penetrate 1 wall in another direction as window so I would get signal from house near by. Or that if I use antenna in the attic I would detect ap signals from at least 1 km away, but I don't. 500-600 m at best.

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,,,for which this antenna must be placed at a height and not have obstacles in front ... !!!!

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Your cable (connectors) seems to be badly assembled (happens to the best, there is usually a QC to avoid this), the central pin has 191,8 ohm !!!!!

It should tend like the other conductor to 0 ohm!!

and check that additionally, you don't have a problem with SMA to RP-SMA

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Hi Guys!

Yes it is good advice to place antenna high and without obstacles I agree. But I still think is something with connectors(like you said swarg_eu), tried to solve it and need to test more.

For testing I used 3 antennas in the same spot a few cm from the window. They were directed at the same or similar spot. I used linux software linSSID, which has nice graphical representation of signal quality and min, max ranges. The adapter was Alpha NHA. The antennas were: Alpha 5-7 dBi  omni directional stick, Alpha 7dBi directional one and 18-21 dBi directional square panel antenna.

The omni directional stick performed the worse. Suprisingly 21 dBi one performed worse than 7 dBi directional. The 7 dBi directional was pretty good one. I get a lot of signals from different directions, much more than from 21 dBi one. If I point it in the same direction as wifi router is positioned in the house(different room, different floor) I get great signal quality, better than from 21 dBi one. In longer distances the quality varies. In some cases if I point panel 21 dBi antenna in the right direction the former wins, but not always. I am really suprised that if I point larger 21 dBi antenna from window to another neighbor house, which is 100m away without obstacles I get only 80 PWR tops on airodump or linSSID. I was expecting much better signal. 7 dBi panel antenna gives me 76 dBi tops and seems more consistent.

The problem is most likely cable, however,.... I am still searching online stores to buy direct adapter so I wouldn't use any cable. I need male BNC from antenna and female SMA to adapter. It is almost impossible to find one, been searching it a lot. The problem is female RP SMA, beacause I can't find the right one, so I could screw the adapter on it, the thread has to be the opposite. 

I have been searching https://www.tme.eu/en/, but haven't found the right one. If someone posts a link to eu based store so I could buy the right one I would appreciate it!. 

 

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On 10.04.2022 at 6:43 AM, Admin said:

,,, this antenna is one of the best, I wonder why it doesn't work for you...!!!!???

screenshot_1194.jpg

,,,, with 2x2 such antennas I don't think it has a gain of 21dBi but only 18 dBi....

screenshot_1195.jpg

wow can you share this model pls?

 

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