mk808 - My external antenna mod (not working)

[robs23]

Hi there. After reading some comments here on replacing original antennas with new ones, I decided to do my own mod. First off, I just soldered SMA connectors to original antennas, and thanks to those SMA connectors I was able to connect external antennas (like those dedicated for routers). It worked, sometimes great but very often signal dropped as much as it did before mod. So I decided to unsolder original cables and replace them with completely new ones. I decided to use cooper multi-core wires because these were the only ones I had. I soldered them only to both ANT pins (didn't use GNDs). When I rebooted my device, it couldn't find ANY network. I tried restarting but it didn't help. So what have I done wrong?
1) should have used single-core wires?
2) should have soldered GND as well?
3) maybe it's because of my poor soldering skills? Did I create cold soldering? Doesn't cold soldering transfer signal at all?
Below are few pictures of what i did.

[lukesan]

Seems you don't know anything about HF or antenna's. Coax is there for a reason!
And no you can't take a multimeter and measure if the coax is 50 or 75 Ohms.
That is lesson number one ;-)

Carefully take both wires off so you don't damage the pcb and read the sticky note (http://www.freaktab.com/showthread.p...help-you-do-it!) in this forum about replacing the antenna.
Yes, there are some real geeks in this forum but I don't recommend you do the freaky ones unless you have the right equipment.
The wire you use is dangerous since it is heavy and might take off the conductive path off the pcb.

If you don't have a thinner wire you can experiment with just cutting a network cable (I have plenty around always) and use 1 of these wires inside of that cable. Longer is not better (another HF lesson) so approx 3 to 6cm will do.
As someone else noticed they used a 0 Ohm resistor to connect antenna's in the original design, well that doesn't work so just try with 1 piece of small wire soldered to the 'ant'.

[ADD]

... 3) maybe it's because of my poor soldering skills? ...

Sorry my friend, but more likely this is exactly the reason. Normally, even with removed antennas you should see some APs. You must have grilled the wireless chip with soldering iron. I realy hope that I was wrong though ...

[robs23]

lukesan, ADD - thanks for pointers, I wish I had asked before haevy modding though:/ Well, to be honest, I decided to solder on pcb only because I knew that there are always other possibilities (ethernet, WLAN stick via USB) in case I grilled chip..
I'm just thinking.. maybe it's just the pcb is, well, dirty a little bit and it would do if I cleaned it up? How I can do so safely?

[lukesan]

lukesan, ADD - thanks for pointers, I wish I had asked before haevy modding though:/ Well, to be honest, I decided to solder on pcb only because I knew that there are always other possibilities (ethernet, WLAN stick via USB) in case I grilled chip..
I'm just thinking.. maybe it's just the pcb is, well, dirty a little bit and it would do if I cleaned it up? How I can do so safely?

Like ADD said be carefull!

To be honest put the MK808 aside for a couple of hours and take a pcb of something that is already broken.
I keep a lot of stuff for future use (since it always breaks down in the evening or Sundays)
Start practicing on other components on that broken board so you get a feel what is happening, every solderingstation heats up differently but you will gain skills in this rapidly.
You will see that when you heat up a soldered component to get it out if you add solder it will start to flow quicker making it easier to get it out. (watch your fingers!)
A good solderingstation is always a bonus. I own a couple but my oldest Weller is now about 30 years old and still working properly.

Now to clean excesive solder or junk.
Couple of ways. You have special cheap tools for this or you can strip off the other part of the tv coax and let the solder flow when you heat it up if you hold it to the pcb. .... but heat is also not good so don't in this case.
If it looks ok then go to the next step (take a photo in case you are not sure and post it)

I would take off both wires without heating up the rest of the components too much.
Then take that little wire (network cable) and strip it just a bit so it is not able to touch other components. If you have stripped it just tip it with a solder before you solder it to the pcb.

[robs23]

@lukesan, once more thanks for pointers, I appreciate very much. I'll give it another try later in the evening or tomorrow. Will definately get back here with feedback. I'm counting on your further remarks!

[robs23]

OK, it took longer than I expected but I think it was really hectic time for all of us, right? I did some cleaning up and you can see results in pictures. There are still blur areas around ANT and GND but I think it is rather melted pcb than any junk/solder.. Please verify what I've done.
@lukesan : I have another question - can't I just use tv coax to solder it to pcb instead of network cable you suggested?

[lukesan]

OK, it took longer than I expected but I think it was really hectic time for all of us, right? I did some cleaning up and you can see results in pictures. There are still blur areas around ANT and GND but I think it is rather melted pcb than any junk/solder.. Please verify what I've done.
@lukesan : I have another question - can't I just use tv coax to solder it to pcb instead of network cable you suggested?

Talk about busy days!

Well don't worry about the stuff on the pcb. No real need to clean it up since it doesn't conduct or shorten anything.
Please don't solder tv coax on the thing because it will create mechanical stress on the conductor that is on the pcb and causing the possibility that you destroy your device!
The simple wire should do the trick. Solder that to the 'ANT' and leave the 'GND' like it is.
Test the stick without the cover and if it works ok you can drill a small hole in it to guide the wire through it.
You can see photos from mine in the zip file http://www.armtvtech.com/armtvtechfo...start=70#p4368

[robs23]

OK, I've tried to find some access points without any antennas soldered to mk808. It didn't find my router. I turned my galaxy s into mobile router than, put it directly next to mk808 and then it showed it's SSID! So it's not grilled! Now I can solder a wire from network cable as antenna. I believe you were writing about 1 of those colorful wires in the picture? And exactly, why only 1 antenna and not 2?



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UPDATE: ok, I've soldered little white wire (like one of those in picture), soldered SMA connector and mounted external antenna and... there's no signal I must be the worst solderer in the world. I don't get it, this time I made everything as it should be. Of course the quality of my solder on pcb may be not first class, but I think it should work anyway..