Chip removal to add external antenna?

Good Morning,

If I remove (desolder) the WTC blue brick antenna from the end of aa
ABS NW-200-USB adapter I am left with two copper pads. One looks to be
just support to anchor the chip and the other end is at the end of a
series of capacitors and an inductor. I assume I solder the driven
element to the end of the series of Capacitors and inductor. I would
think I need to connect the ground side of the antenna (other half of
the dipole in the Yagi) to something. I bought three of these from
Newegg in case I smoke the first one.

Any other guidance on connecting an external antenna to this would be
greatly appreciated. Is a Yagi the best choice?

Vance

I can e-mail a picture if needed.

On 2 Oct 2005 09:07:45 -0700, "Positron" <vburnham@gmail.com> wrote:

>Good Morning,

Yaaaaaaaawn.... Thinking before coffee is difficult.

>If I remove (desolder) the WTC blue brick antenna from the end of aa
>ABS NW-200-USB adapter I am left with two copper pads.

Yes. There are only two connections to the anteanna. One is ground.

Are you sure it's labelled WTC? That's a Centurion part but not
exactly the correct antenna:
| http://www.centurion.com/home/antennaProd/wtc2450.asp
Perhaps WIC would be more accurate?
| http://www.centurion.com/home/antennaProd/bluechip.asp
| http://www.centurion.com/home/pdf/wic2450.pdf

>One looks to be
>just support to anchor the chip

Correct. For that particular antenna, it's just a very compact 1/4
wave radiator. The anchor pad can be ignored.

>and the other end is at the end of a
>series of capacitors and an inductor.

That's the matching network to compensate for any mismatches between
the radio and the antenna.

>I assume I solder the driven
>element to the end of the series of Capacitors and inductor.

Correct. First, make sure there's no DC sitting on the antenna
connection. There probably isn't be check anyway. If using a coax
pigtail (recommended), be sure to keep the exposed part of the center
conductor as absolutely short as possible.

>I would
>think I need to connect the ground side of the antenna (other half of
>the dipole in the Yagi) to something.

What yagi? Find the closest ground connection and use LOTS of
grounding to the braid.

>I bought three of these from
>Newegg in case I smoke the first one.

Learn by Destroying. You must sacrifice one to learn how to do the
others correctly. Without sacrifice, the radio gods do not deliver.

>Any other guidance on connecting an external antenna to this would be
>greatly appreciated.

Use very small coax and keep the exposed leads VERY short.

>Is a Yagi the best choice?

I have opinions on the releative merits of yagi, dish, and patch
antennas. Each one depends on what you are trying to accomplish and
what you have to work with. There are few places where I would use a
yagi.

>I can e-mail a picture if needed.

Don't email. Post a photo to a public web server.

--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Excellent, thank you very much!

I checked and it is WTC. The FCC site has photos at

https://gullfoss2.fcc.gov/prod/oet/f...ive_or_pdf=pdf

The second picture shows the WTC chip at the lower left ahnd corner of
the circuit board.

Thank you again!
Vance Burnham

Positron <vburnham@gmail.com> wrote:
> Good Morning,

> If I remove (desolder) the WTC blue brick antenna from the end of aa
> ABS NW-200-USB adapter I am left with two copper pads. One looks to be
> just support to anchor the chip and the other end is at the end of a
> series of capacitors and an inductor. I assume I solder the driven
> element to the end of the series of Capacitors and inductor. I would
> think I need to connect the ground side of the antenna (other half of
> the dipole in the Yagi) to something. I bought three of these from
> Newegg in case I smoke the first one.

> Any other guidance on connecting an external antenna to this would be
> greatly appreciated. Is a Yagi the best choice?

> Vance

> I can e-mail a picture if needed.

Another way is to use the trace included on the backside of the board
next to next to c44/c57 that looks like a bullseye,turning c49 90 degrees
would direct the output to the center through the gold plated via.
an SMP type "catchers mitt" looks like it would fit,possibly others but
you get the idea.. it would be harder but less lossy than just soldering
coax to traces

On Sun, 2 Oct 2005 19:55:54 +0000 (UTC), Luddite <a2k@ripco.com>
wrote:

>Another way is to use the trace included on the backside of the board
>next to next to c44/c57 that looks like a bullseye,turning c49 90 degrees
>would direct the output to the center through the gold plated via.
>an SMP type "catchers mitt" looks like it would fit,possibly others but
>you get the idea.. it would be harder but less lossy than just soldering
>coax to traces

I sorta agree. The center of the "bulls eye" is an RF test point used
in the automagic production fixture. It's probably a decent place to
grab the signal. There's plenty of ground around it for the coax
shield. It appears to be coupled to the matching network with a small
capacitor (C11), which may be too small to couple all the RF as long
as the matching network is still present. Methinks you may need to
lift C49 or preferably, cut the trace to C49.

I'm a big fan of semi-ridid 0.141 coax cable with SMA connectors for
such things. If semi-rigid is unavailable, a piece of RG-174/u,
RG-188/u, or RG-316 coax will work.

Incidentally, if you wanna try something really ugly, don't bother
with the coax and just build a dipole. This would go near where the
blue antenna thing (removed) went. One 1/4 wave element is connected
to the RF lead, perpendicular to the board.. The other to the ground
forming a dipole. Each are 3.1 cm long. It should give a few dB of
gain.

--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558