Plug in U.FL pigtails

Is there a trick to plug in the SMA/U.FL pigtails into the U.FL connectors on the PCB?
After ten unsuccesful minutes I need a break…

I don’t have stubby fingers but this is very frustrating… :frowning:

Ooh no!!
One of the coils on the Tx part is demolished now!

One of the successful connected U.FL pigtails ruptured the coil.
The LimeSDR is scrap now!


@DL8WOW - Jens,

The LimeSDR board is NOT scrap now, a new transformer can be had from Digikey or Mini-Circuits and they’re quite cheap (something like $3.00 USD). It’s not that hard to replace the transformer even if you’ve messed up the pads on the board. Just obtain the V1.4 schematic for the LimeSDR board here:

There is also a BOM (Bill of Material) in the same subdirectory as the link I sent you.

Again, to recap, your board is TOTALLY FIXABLE. Obtain the info for your transformer that’s bad (which one), look it up on the BOM, and the replace it based on the schematic.

Hope this helps - 73 de Marty, KN0CK

P.S. I used a set of tweezers to locate the U.FL connector to the jack on the board and used the eraser (rubber end of the pencil) to set the U;FL plug to the jack until I heard it click- NEVER had an issue doing it with 3 boards now.

73 - MJW


Hi Marty,
I will try it.
But it seems that also 4 of 10 U.FL connectors are either deformed or out of tolerance. It was not possible to click the pigtail plug into the U.FL connector.

I think I have to order also additional pigtails and U.FL connectors… and SMD soldering equipment…Soldering of SMD is the next challenge.

73 de DL1WW (ex DL8WOW)

I found mine quite difficult to get on.
I ended up using the handle end(flat part) of my tweezers to help get them on, just clipping the back part over a little first then pushing down with the tweezers. You need to be really mindful of those indictors while doing it, cause they don’t take much to break.



Could you post a picture of board area with damaged components, please.

Mmh… the damaged device is T2

Unit price : 6,95$ but mimimal order quantity 20 … (

Alternative suppliers with branch offices in Europe like Mouser, Digikey or RS Components are not able to deliver this component. :frowning:

Yeah, this one is really damaged, sorry.

@DL8WOW - Jens,

Actually, when I look at the photograph you have two options here:

1.) Just replace the matching transformer with a new one from either Mini-Circuits or Digikey

2.) There is hope for the remaining leads on the transformer - they’re just sheared off at where they connected onto the pads on the board. It may be possible to heat up the ends of the wires (they’re bent around, but they’re in the approximate location where they were sheared off), add a little solder, and then heat them up enough to solder to the pads. It won’t be ‘factory fresh’, but it’s at least going to give you back the Lowband port on Receiver 2.

By the way, NEVER think that your Lime is scrap because of something like this. You have MANY more ports to use on the Receiver 1 and Receiver 2 port sides (in your case the Wideband and Highband ports) and both will suffice for V/UIHF and with the mods HF. A simple fix to this Lowband Port on the Receiver 2 side and you will be back to health again…this isn’t terminal.

Heat up your soldering iron and be careful with it - it’s entirely salvageable even as it is and should work just as well as it used to be before the mishap.

73 de Marty, KN0CK

I think I have also to replace some of the U.FL connectors and SMA/U.FL pigtails as well.
Despite careful proceeding some of the U.FL connectors seems to be deformed.

73 de Jens / DL1WW (ex DL8WOW)

I’m not sure about the root cause of my problem.
The SMA-U.FL pigtails come together withe the Luftec enclosure from Shenzen/China and I’ve ordered this in the Online shop of QRP Labs (

Only 4 of 10 pigtails was passably mountable (gently pressure - click - done).

@andrewback @Zack

Gents - Is there any way you can get with @DL8WOW (Jens) and send him a T2 transformer off a scrapped Lime board in your lab? Mini-Circuits has a minimum of 20 part order at nearly $7.00 each - not cheap. Any help you can provide for Jens?

73 de Marty, KN0CK

T2 problem solved!
Minicicuits send an EZ sample (4 pieces)…
Free of charge… from U.S.

73 de Jens


U.FL connectors always scares me plugging them in for fear of damage. I’ve found that it is easy to mess-up the inner female connectors (on the cable side). It is easy to cause the inner female to get it pinched together and then it will never seat. Once that inner connector is pinched the connector to just slide off the PCB connector sideways potentially causing other damage. To fix it the point of a tack or pin can be used to open it up to the right size. Of course, if you get it too wide you will get a poor connection.

I think it was an issue with the tolerance of the pigtail plugs.
I was able to connect new ordered pigtails from DigiKey without any problems.
Four sample items of the T2 transformer reached me yesterday.

I’ve replaced the damaged one.
But soldering the new one is my challenge for the next few days. :wink:

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@DL8WOW - Jens,

Keep on it - It may be a challenge, but it’ll no doubt give you more confidence working with the Lime and that’s a great thing to have on your side.

73 de Marty, KN0CK