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Making a Built In N-Connector Pigtail for your PC

Making a Built In N-Connector Pigtail for your PC

There is a simple way to get an N connector attached to you 802.11 device without the rigmarole of buying expensive pigtail that converts reverse SMA, MCX or whatever to an N connector via a short run of cable. The problem with such pigtails is that they incur an unnecessary loss with each connection of up to 1dB per connector and perhaps 1dB on even a short 1 foot run of thin coax.
Connector removal isn’t for the faint of heart. You can really damage your card doing this, such as inadvertantly ripping out the metal plating in the pin holes or lifting the tracks. The reverse gender SMA connector was removed with a specialised desoldering tool (a hot iron with a hollow tip through which air was sucked through). Be warned, the rear two ground pins had a very good contact with the ground plane on the DWL-520 and so was sinking most of the heat very quickly. This stopped the solder from readily melting and flowing so required a bit of persistence to remove. The front two ground pins and centre signal pin desoldered very easily.

Unlike most other coax which has a braided shield with a plastic sheath, Quickform has a solid silver coated shield with no outer insulation at all. The solid shield ensures very little signal loss and is also readily solderable.

First, cut up the length of cable you require to reach from the card to where you wish to mount the N-connector. You must use a knife in a sawing action so that you get a clean cross section cut without compromising the roundness of the cable. Wire cutters will squash the cable which is totally unsatisfactory and will impede the signal.

On one end of the cable remove the outer shield and inner plastic to leave 3-4mm of the centre core exposed. Cut a small piece (1mm) of the plastic core off to use as a spacer to prevent the shield contacting the signal pad and to provide some mechanical support. The yellow circled area highlights the spacer.

Cut two 30mm lengths of solid copper CAT5 or phone wire. Wrap the centre section of each wire twice around the shield about 15mm from the end of the connector and solder the turns to the shield. Each end of the wires should be spaced to fit the diagonally opposing ground pin hole on the circuit board footprint. You should end up with a five legged end of cable which you can insert into the connector footprint. The four wires provide an excellent ground connectivity and anchor the cable to the card to minimise flex and stress that would otherwise cause the cable to break away from the card, perhaps taking the centre pin hole plating with it.

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