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USB WiFi Antenna Mod Answered

I am working on adding a helical antenna to a cheap USB WiFi adapter.  My question is where do I connect the antenna to existing circuit.  I've attached a closeup picture with three likely points.  My three main questions are:

1) Where to connect the external antenna

2) Do I disconnect the rest of the onboard antenna (my gut says yes) or just add in the new

3) What impedance will the external antenna need to match?  I assume the components between points C&B and B&A are for some kind of impedance matching.

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steveastrouk (author)2013-02-15

That position at B IS for a surface mounted connector, A is definitely an impedance matching network for the antenna, so that the SWR is acceptable. Gotta guess at 50 Ohms.

Steve

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telfon (author)steveastrouk2013-02-15

Thanks Steve. That sounds right. I'll connect the external antenna at B and I can even connect the shield there since it looks like they left that part of the ground-plane uncovered. I'll cut the rest of the antenna network at A out and try to match a 50 impedance.

I bought 5 of these cheap USB adapters online a couple of years ago when they were on sale for $5 or something. If this first one works out I'll right up a nice Instructable converting a couple of other ones.

-- Paul

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killerjackalope (author)2013-02-14

I'm not sure about the impedance bit but it looks like you could easily test it by scraping off a little coating on the PCB touching your antenna leads on, as long as you didn't short anything else I don't see anything too disastrous happening. I tried a few experiments like that with my dongle then put it back together when I needed it... No harm done...

My experiments failed, probably because I have a habit of just slapping things together to see if they work...

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user

The only thing dangerous is putting your dongle where it's not supposed to be.

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user

you are right caitlinsdad. I agree with you

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user

In my defence I totally thought it'd get better reception there...

The doctor believed me, he even raised his eyebrow in belief...

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