Re: Make external connector on a USB dongle

On Sun, 27 Nov 2005 23:02:00 +0100, "Tazzulella"
<tazztuoi@xxxxxxxxxxxxxxx> wrote:

>Uhm... today I've realized this:
>http://tinypic.com/hvumur.jpg

Not great. I see a few problems.
1. You destroyed most of the ground plane. Not a great idea but
probably acceptable under the circumstances.
2. The wire length between the center conductor and where the "cable"
hits ground is way too long. Ground it to something near where the
center conductor hits ground.
3. Where's the shield wire on the coax on the connector?

If you don't wanna use a pigtail, you might try an SMA bulkhead
connector, similar to what you have. However, I would file out an
exact match for the outline of the base of the connector out of the
ground plane you chopped off, with a short coax or direct connection
to L7.

>Ok, it works, but I don't know why...

Without a 50 ohm termination or antenna, the traces on the board start
to look like radiators and act as an antenna.

>with the previuos modify on my PCMCIA
>card, without external antenna the signal was ZERO.

No clue. I've successfully butchered PCMCIA cards with pigtails. When
they don't work, it's almost always a short at the coax end.

>Now, with this dongle, without antenna (the bluechip) I've got signal...
>With antenna mounted (a simple rubber D-Link antenna) the signal is not
>stronger than without...
>
>I'm ready with 3 attemps.
>
>with antenna connected:
>1) at the end of diversity (before the filter)

Nope. You really need the filter. It's not just for cleaning up the
mess from the transmitter. It's also to keep junk out of the
receiver.

>2) at the end of filter (cutting C3)

That's worth a try. C3 is only there for DC isolation of the test
conenctor, which isnt present.

>3) on the SW1 place (cutting L7 and C33)

Good luck soldering the tiny connector that will fit at SW1.

>Next week I'll receive a R&S powermeter 3GHz capable, and I'll to try in
>these 3 positions.

You'll probably get about the same power level from #2 and #3. #1
will yield about 2dB more (filter loss), but without the spec ***,
I'm guessing at the attenuation. I have a home made power meter made
from an SMA conector, some chip resistors, a microwave diode, and a
filter capacitor. Works nice.

>I've also a friend of mine with a Anritsu antenna/power/swr analyzer.
>I'll tell you...

Ooooh... $15,000 and up. Can I borrow it? I'll give it back. I
promise. Maybe.

Otherwise... home made RF test equipment:
http://www.qsl.net/n9zia/wireless/appendixF.html#10


>Thanks again for support: virtual coffe (italian espresso) payed for you.

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

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