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How can I reconnect loose antenna cable

rfcable
coremodule
Tags: #<Tag:0x00007fefc3be1698> #<Tag:0x00007fefc3be13f0>

#1

Hi guys,

some days ago, my Fairphone 2 fell to the floor. This damaged the RF cable connecting the antenna to the motherboard. The cable is now detached from the connector (probably MHF3). I tried to stick the cable back into the connector manually, but it did not work. I read here that @PorCus managed to re-attach it. Was this referring to re-attaching the connector to the antenna board or the cable to the connector? If attaching the cable to the connector manually is possible, could someone please explain how to do it?

Kind regards,
Matthias


#2

Has one flange that created crimp marks in black insulation broken off the connector? Are there thin copper wires visible outside the soldered tip by edge of black insulation as slightly blurred here?


#3

Hi @aspergerguy,

thanks for the help and sorry for posting a blurred picture. I hope these ones are better.

There are still thin wires next to the black insulation. When I tried to insert the cable into the connector manually, I could see how those cables where curling and did not go into the connector. As visible on the photos, there however is the main white/silvery strain of cables that seems to be unaffected by the rip (which in that case is rather a pull out than a rip off).

Does this answer your query?

Kind regards,
Matthias


#4

I’d look out here in the marketplace for a defect core module (assuming it still includes an intact antenna cable).


#5

@urs_lesse: thanks for the hint, I started looking.


#6

Maybe you know someone who is capable of doing some proper soldering.


#7

Yeah, I am already looking for workshops that can do this.


#8

Any repair-cafe around there?


#9

Did you try soldering the cable by yourself?
The reason I ask is that antenna connectors shouldn´t be soldered related to the attenuation.
I guess you are German, so here is some footage about how an antenna works:
http://www.elektronik-kompendium.de/sites/kom/0810171.htm


#10

@ElKrasso: Thanks for the hint about the soldering. Luckily, I neither did nor considered it :slight_smile:

But if I interpret this video correctly, those connectors are rather crimped than soldered anyways.


#11

…correct

…also correct

But they speak of “cold solder joints” which are a sign of improper soldering. Usually such antenna connections are crimped, but at some point they start with a solder joint (on the PCB the socket is soldered onto not crimped into the board as I assume).
And a completely torn apart cable will surely result in an attenuation of 100%.
So if there is no proper replacement cable, soldering can help a bit.


#12

but will have an effect on the reception, I guess.


#13

@Patrick1: Thanks for the clarifications. Now I get all the remarks about soldering.

From what it looks like, the socket really is soldered to the PCB. The connection however looks solid and undamaged. The connector can also still be attached to the socket by simply plugging it on and off. My issue is rather with the connection between the cable and the connector. So I guess I am stuck with two options.

  1. Get a used FP2 antenna cable from Fairphone support or a member of the community.
  2. Find a workshop or repair café that have a crimp tool and an MHF3 connector to repair my current cable.

Anyway, thanks for the support, guys. If anything works, I’ll make sure to post it.


#14

My phone is working again, yeah!

For the record, I went with both options in parallel.

@Freubert was so kind to send me a spare antenna cable of his phone.

While on the way, I also went to a repair shop to see, whether they could fix my original cable. They could not. However, they gave me a simple RF cable with MHF3-connectors. Interesing enough, this cable works, although it lacks the PBC attached to the original Fairphone antenna cable. Does anybody know, what this board is supposed to do? Apart from this suspicion, I could not find any information about it. The antenna seems to work perfectly fine without it, though.

Original fairphone cable with mysterious board in red frame. The antenna board on the right can be easly plugged off and on again.

Cable I got from the repair shop (similar) without mysterious board.

Cable

I’d love to learn, what the heck this PCB does. Is there a captain here?


#15

Interesting.
Did they customize it to the required length themselves, or is this a ready-made part of some sort?
What was the price you paid for it?


#16

It was about a centimeter too long. But I just curled the excess length of the cable under the antenna board.

He offered it for free. But after seeing that it solved my problem I gave him 10 €.


#17

It seems to be the antenna for Wifi reception.

Here some Wifi antennas with a type of MHF connector can be found.
As many antennas does not only need the signal line but also a connection to ground this small pcb seem to do nothing else than hold the two wire ends and provide contacting pins for grounding to the back of the display.

The thing with antennas is, they have to be matched with the signal which they want to receive/transmit/transceive etc.
So the signal has a specific wave length according to the frequency band (2,4GHz/5GHz) here. To have the best reception the antenna needs to have a specific size/length. Too short may not work properly, too long as well.

Specialists are talking about things here like Lambda/Lambda 1/4; Lambda 1/2 etc. Huge technical playground for those enthusiasts.

So in your case there may also be some luck involved. Good for you.
Thanks for your feedback.


#18

Three months on, I’d be grateful to hear if your FP2 still works with the alternative antenna cable, @MatthiasBremen ? I’ve had people giving up on their FP2 recently just because there was an issue with the antenna, so I’m pondering whether to write a pre-emptive note encouraging others not to give up early should they be affected in the future.


#19

Hi Urs,

that is a cool Idea. My Fairphone 2 is still working perfectly fine with the replacement antenna, although there is no PCB on it compared to the original antenna cable.

Best,
Matthias