1
\$\begingroup\$

I have made my own Yagi antenna and I would like to see if it works or not. I made the antenna based of these instructions: Easy to Build WIFI 2.4GHz Yagi Antenna

So I have soldered a coax cable to the pin 2 (the driven element). The center connector to one side and the shielding to the second side of the paperclip. But I have no idea how to actually connect it to my wifi dongle.. Does the center connector of the coax go to the "on board antenna" and then the shielding to the USB ground? also is the antenna the trace to the left of the dongle? The wifi dongle is an old Netgear w111v3. Any tips for me? Thanks!!

enter image description here

enter image description here

|improve this question
\$\endgroup\$
  • \$\begingroup\$ That antenna design might accept 50 ohm or 75 ohm coax. You have no assurance that any part of your 2.4 GHz wifi dongle is compatible with this impedance. You might be able to guess how to match impedances if you have a schematic. \$\endgroup\$ – glen_geek Aug 24 '17 at 16:51
  • \$\begingroup\$ Thanks for your answer. Well i just wanna test it out.. Lets Say that it matches. I just wanna know how to connect it. \$\endgroup\$ – Xane Aug 24 '17 at 17:08
  • \$\begingroup\$ A Yagi is a balanced antenna so you will need to at least consider using a balun before you attach it because, quite possibly, the antenna etched onto the PCB is fed from an unbalanced output. \$\endgroup\$ – Andy aka Aug 24 '17 at 17:16
  • \$\begingroup\$ Hmm what does that mean? Wont it work at all if its unbalanced or will it just dont work as good? \$\endgroup\$ – Xane Aug 24 '17 at 17:30
  • \$\begingroup\$ A1 looks like it's supposed to be populated with a coax connector of some sort. \$\endgroup\$ – Ignacio Vazquez-Abrams Aug 25 '17 at 22:26
3
\$\begingroup\$

possible RF connection The solder-resist is absent from the marked area, suggesting that this connection point may have been used by the manufacturer to verify that this dongle meets a RF specification. It appears to be close to the antenna feed point.
That said, there's no way to tell what impedance the RF sees at this point, or how you could impedance-match to this point.

Andy has pointed out that a balun would be good where you attach the unbalanced coax to the balanced driven element. This could be a ferrite sleeve slipped over the coax. There are alternative balun approaches. Unbalanced drive can skew directivity.

A caveat: Any blog boasting easy-to-build 2.4 GHz directive antenna is suspect. Your antenna is a very narrow-band design - measurement tolerances are critical, and impedance matching is difficult.

|improve this answer
\$\endgroup\$
  • \$\begingroup\$ That explains it Thank you! The reason Why i wanted to try This. Is because i tried using a food strainer to focus The signal and it actually worked.. Picked up a lot of wifis if i focused it. Then i thought if a food strainer works Maybe i can build one antenna of my own.. I Didn't know it was going to be This Hard.. \$\endgroup\$ – Xane Aug 24 '17 at 17:58
  • 1
    \$\begingroup\$ The most wise RF engineers will tell you RF is like magic. If you have a wizardous understanding of the how and why, and the needed measurement equipment, you will eventually come up with an improvement or even … a solution. If you lack any of these, you will create a thing which is out of control. \$\endgroup\$ – Janka Aug 24 '17 at 19:26
  • \$\begingroup\$ One more quesiton.. do you guys know where the middle connector of the "RF connection" goes on the circuit board? I would like to solder a wire to it, but the small dot is too smal for me to get a wire there.. I tried using a multimeter to trace and see where it goes but i couldn't really find anything.. a bit confused hehe. Thanks. \$\endgroup\$ – Xane Aug 30 '17 at 15:44

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.