I cracked open an el cheapo Dick Smith XH7918 card to add an external antenna socket. From the pic, you can see there is provision for a socket. I want to use the card for antenna measurements, therefore want to remove both internal patch antennas ( by removing the coupling caps to each ).
1) Should the unused (RH) antenna feed be terminated in some way, or just left open?
2) There is provision for two smd devices in series in the feed to the external antenna; any ideas on components / values? My guess is a cap of about 5pf, but why two pieces?
3) Anyone know where you can buy (in NZ) pcb mount RPSMA connectors?
I will see if i can find out what the actual values and the configuration is supposed to be. we canb get some SMA pannel mount connectors BUT they are not cheap. ON the up side the SMA connector for the cable is a little cheaper and we have them fort LMR-195 and 200 so you get less loss.
I cracked open an el cheapo Dick Smith XH7918 card to add an external antenna socket. From the pic, you can see there is provision for a socket. I want to use the card for antenna measurements, therefore want to remove both internal patch antennas ( by removing the coupling caps to each ).
1) Should the unused (RH) antenna feed be terminated in some way, or just left open?
2) There is provision for two smd devices in series in the feed to the external antenna; any ideas on components / values? My guess is a cap of about 5pf, but why two pieces?
3) Anyone know where you can buy (in NZ) pcb mount RPSMA connectors?
I tried this on my DSE one
I pulled the capacitor off the other antenna and used that for the second component.
However, it seems that the config that the drivers use, means that the other antenna is active, not the one you have replaced with a socket. Recieve sensitivity is good, but transmit seems to come from the stub left on the board.
There may be a reg key to fix this or something, i lost interest.
I pulled the right angle reverse SMA socket off a bust PCI card.
Thanks guys, for the suggestions: I had a look in the RS catalog previously and they want $16 or $35 for SMA PCB mount sockets - strangely SMB or SMC sockets from them are only around $4.50; so may go with one of those.
The SMC (card not connector!) mod adding the 2 x 150pf caps looks closer than the dwl-650 mod I was looking at. The DSE card indeed has inductors, not caps, feeding the two internal patch antennas. Out of interest, there is a schematic of the dwl-280 here .
Use the SMA PCB socket for your connection as the screw fitting won't come off as easily and it's a common type.
You will need a capacitor to add to your circuit board as you can see in your photograph. You can remove one (if you have the patient and time) from the other antenna circuits or just buy a new one.
The pads that the sufface mount devices solder to won't take too much heat before they get destroyed. The component needs to be in place and just touched on the soldered ends to set it.
I'm looking to do this mod to the same card this week, as I need a PCMCIA card with an external antenna this weekend, and have got two of these cards lying around not doing alot -- any tips?
damn. i think dse stopped selling these coz i'd expect people bought them (being cheap) then modded to fit an external antenna. i have a dse xh6821 (DSE $69) and it doesnt have a place for an SMA PCB mount
The capacitor is rated at 5.6pF ceramic ( one picofarad = 0.001uF). It's case size is classed as 0402.
Didi it work? It seem to go O.K.
You must be careful soldering these components. I have mad changes to my boards 4 times. They went out in the trash 2 weeks ago as I was not prepared to spend money on SMD equipment for repairs.
But thats how things go
I was only using them for a peromace tests anyhow.
I accidently lost one of 2 small capacitors (while soldering them off) when I was trying to attach an external antenna to a DWL-650+ based on the info found on nzwireless.org and other pages around the net.
I was wondering if you might know how to find out what values these elements have so I can buy replacements.
damn. i think dse stopped selling these coz i'd expect people bought them (being cheap) then modded to fit an external antenna. i have a dse xh6821 (DSE $69) and it doesnt have a place for an SMA PCB mount
I have one of these and it doesnt appear too hard to modify...
I'm contemplating aquiring some SMD equipment to make this task easier, but to justify the purchase I was wondering if anyone would be interested in one of these cards with a builtin pigtail?
They would look something a little like this prototype (it's awaiting testing)
I apologise for the image quality, my flatmate has buggared off with my digicam :roll:
Anyway, I was thinking of maybe in the region of $80 plus p&p.. warranty would not be covered obviously however each would be tested prior to postage. (Consider that the cards are $69 and the pigtails are $26ish)
I could also offer a parallel service of modifying other wifi cards for like $20 including p&p.. again no warranty or implied guarantee of success...
Oi whetu, you got info on how to build one of these pigtails in? I have the same card sitting in front of me, its got these really tiny SMD pads to connect something to, but i dont know how to do this without buggering my card, can you help with instructinos?
No offense, but by the time that you have moved flat, i'll probably have re-done the card with new labels and blue LEDs. anyone know where i can find a backwards pigtail, as I really want an RP-SMA connector to let me attach the standard stub antennae that PCI cards use
1) rotate the capacitor. If you follow the trace back from one of the prongs you'll come to a capacitor. at right angles to that is a trace out to the external antenna pads. Rotate that capacitor, pop the antenna jack/cable on and you're away. (This would be similar to a dwl-650 mod.. google it) I have done this and so far have had limited success...
BTW you dont need the capacitor.. it's there to qwell static discharge and the like from wrecking the small IC between the antennas and the rest of the card.. if you lose the caps, just make a bridge of solder and you should be away laughing
2) simply solder straight on to an existing antenna prong.. looking at it with the pcmcia connector facing away from you, there should be a small golden dot on the left side. At a guess that may connect to the ground layer that may be on the opposite side of the PCB. The theory goes that you scrape and tin the left prong and that dot, affix accordingly and you're away. I have not yet proved or disproved this theory yet but it would be a considerably easier way to do it
The pigtail can be got from tricky dickies for about 26 bucks.. or cheaper if you know who to deal with
hmm well having gone out and tested this car on a wardrive with Techie, when compared with the dwl650+ we have been using, this card is a bit of a disappointment. It's nowhere near sensitive enough and you literally have to be on top of an AP before it picks up. The dwl650+ will pick up things blocks away...
I'm going to look around and see if there are better drivers for this card, but in the meantime I'd recommend you dont even bother modifying this card.
As an example my manager has this same unmodified card in her laptop, she can pickup the cafenet AP on the first floor of our building but that's it. I have a telecom standard issue PDA on my desk with a sandisk sdio wifi card in it, and last night it picked up several AP's, including a wide open gateway about a block away
Although I have thought lately about getting rid of the surplus equipment there.
I am a project engineer (contractor) and have been importing my own equipment for a number of years, not operated it as retail for the last 12 odd years.
When I order for a project I always round the qtys up to std pack sizes.
As I tend to purchase from wholesalers.
Modding PC card for external antenna 
Linear Mode
