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Adding an External Antenna - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

Amateur Radio | Antennas | Circuits & Components | Systems | Test & Measurement

 Post subject: Adding an External Antenna
Posted: Wed Nov 02, 2005 2:02 pm 

Joined: Wed Nov 02, 2005 1:50 pm
Posts: 11

I've tried this question on a few wifi forums - to little avail.
I believe it's pretty rudimetary stuff, but I haven't much
technical background.

This is an image link to the inside of my wifi radio. ... ficard.jpg

It is a small USB driven device with a little flip up antenna.
Thin grey antenna coax in the upper left is connected just
to the left of what looks like a "hirose" connector on the board.
Between them are a couple of surface mount components.
I'd like to make use of an off-the-shelf 2.4GHz
external antenna.

What is the function are those SMCs in the path between the hirose connector and the mini antenna? Is that mini flip up antenna a different impedance than what would be expected to be attached to the hirose connector?

It looks like I might not have much luck locating a perfect match for
the onboard hirose without having an extremely expensive pigtail custom
made. Any reason why I should not simply remove the hirose and solder
in a permanent pigtail right to the board?

Thank you very much for any advice you can provide.

Kirt Blattenberger
 Post subject:
Posted: Wed Nov 02, 2005 4:22 pm 
Site Admin
User avatar

Joined: Sun Aug 03, 2003 2:02 pm
Posts: 308
Location: Erie, PA
Greetings wsemajb:

That connector is a 50-ohm test port used during production. Inserting a mating test connector disconnects the through port on the PBC and routs the signal through the connector and onto the PCB to the right (in your photo). The SMCs around it are for matching to 50 ohms. There is probably at least one inductor to ground that is used for ESD (electrostatic discharge) protection.

Your best option is to solder your external antenna cable in place of the gray coax. The interface is 50 ohms, so as long as your external antenna is also 50 ohms, you'll be OK. If you want it to be detachable, then install a coax connector (SMA would be good) on the gray cable.

BTW, who is the manufacturer of the PCBA, and what WLAN chipset is on it?

- Kirt Blattenberger :smt024
RF Cafe Progenitor & Webmaster

 Post subject:
Posted: Wed Nov 02, 2005 10:32 pm 

Joined: Wed Nov 02, 2005 1:50 pm
Posts: 11
Thank you Kirt.
So the grey coax is essentially the same feed as that provided through the Hirose connector? In other words, removing the hirose and hardwiring coax in its place would be more easily accomplished by simply connecting a 50ohm pigtail in place of the grey coax?
Thank you very much for the advice.

It's a Senao USB unit. I believe it uses the Atheros AR5005UG chipset.
The unit is not widely available yet. It's offered as an external antenna
version as well, but If I am only able to acquire the version without, I'd like to be able to add an aux antenna if necessary.
Thanks again

Posted  11/12/2012

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