Hallo everybody,
i searched a lot but found contrddittory infos on where to connect an external antenna disabilng the printed one (or two) on the circuit board. Some says the signal must be taken b4 the capacitor, others after.. before or after the the signal splits?
can someone give me a hint ?
see my card here:
tnx in advance
happyCoder wrote in news:ad88b726-7286-433b-a371- snipped-for-privacy@x41g2000hsb.googlegroups.com:
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You don't have permission to access /wifi-card-external-antenna_2.jpg on this server.
arghh sorry,
now jpgs are readable..
I'm not sure if there is any good answer here. The antennas have a shorted matching stub. You can see the trace terminate at the ground plane. So how do you know the RF is set up for say 50 ohms? I guess the question here is do you want the thing to more or less work, or work well?
If work more or less is the answer, I would first determine which antenna is used for transmitting. Manny of these cards receive on either antenna, but only transmit on one.
It would be far simpler just to buy a card with a RF jack. There is much effort involved in building an antenna, so unless your time has no value, I wouldn't mess with this card.
Did you remove the PIN diode switch chip (6 pin IC at the junction of the two antenna feed traces) or is the chip on the other side of the board?
I would remove the PIN diode switch, which is only useful for diversity receive, and attach the antenna to a coax pigtail to the trace coming out of the radio section (shield). The switch and PCB traces are good for a few dB of loss, which connecting directly should eliminate. However, there may be DC on the lead from the radio so it goes through a small value ceramic capacitor at the very end of the trace. Keep the exposed coax leads very very very very short.
hallo Jeff, no I did not removed any chip and there is no chip on the other side, image 1 shows it clearer than image 2
plz clarilfy: do I should connect a capacitor at the end of the trace out of the rf box ,and then the coax ?
but what about that unsoldered place for - i think - a female board connector noticeabe in the middle of the card ? il has gnd and singal ready to be soldered to the coax.
@sushi.com, anyway this is a spare card and I want to solder a pigtail with female, I already own antenna with male connector
tnx guys!
That area is otto focus in both pictures. Looking at the otto focus photos, it looks like the center trace (from the RF box) goes nowhere. Does this board currently function? It looks like the PIN diode switch is literally missing and the center trace (from the RF can) goes nowhere.
For my own curiosity, it would be interesting to know the maker and model number. Extra credit for supplying the FCC ID number so I can look at the photos on the FCC ID web pile and see if the diversity switch is present.
See the trace coming out of the RF box? At the very end of the trace, sorta in the middle of where the PIN diode diversity switch would normally sit, goes a chip capacitor. No clue as to the exact value but 10pf is about the maximum. The other end goes to the center lead of your coax pigtail, unspecified connector type, or whatever you're attaching.
Yep. That's the "test connector". On most boards, there's a Hirose U-FL connector for the purpose. On your board, it's also missing. You could use the test pads *IF*:
Depending on the antenna design, the DC could be tolerated. For example, if it just went to a whip, I don't think DC would be an issue. A biquad would be a problem.
It looks like there are AC coupling caps at both antennas. That is, it goes through a cap, then sees a cap shunt. An inductor shunt as well, not that it matters.
I like your idea of just whacking the center trace. Less is more.
I wasn't thinking so much about what happens when he attaches a grounded or DC short type antenna. That would certainly be a problem. I was thinking about zapping the RF circuitry inside the RF can with a static blast when I touched the antenna. I've done this a few times (mostly with GPS prototypes). The small capacitor limits the energy that can be delivered from the antenna connector.
Did you notice the missing diversity switch IC? How does this thing work?
Yep.
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