22/09/2013 Page 1 WF’s 703n external antenna modification The Chinese market TP-Link703n 150n USB router is a robust, small, low power and reliable router. It may be flashed from its Chinese firmware to TP-Links 3020 English firmware or DD-WRT or OpenWRT or OpenWRT based firmwares like Gargoyle and ROOter etc. It is powered by 5 volts and supports a single 100Mb LAN/WAN port, a USB 2.0 port and a micro USB port for power connection. The 703n has an internal inverted F ¼ wave length PCB etched antenna. There is no external antenna connection. This tutorial documents the necessary modifications to add a standard RP-SMA antenna socket to the 703n. The inspiration for this modification largely comes from these two blog articles: http://blagg.tadkom.net/2012/09/01/wr-703n-external-antenna-mod-diy/ See comments by luno http://blagg.tadkom.net/2012/09/15/better-wr703n-antenna-mod/ See comments by Diarmaid Ó Cualain The 703n’s internal PCB etched antenna is an inverted ¼ wave dipole fed at the 50 ohm impedance point by the PCB tracks. C29, C31 and C32 are a Pi impedance matching circuit. Essentials of the modification
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22/09/2013 Page 1
WF’s 703n external antenna modification
The Chinese market TP-Link703n 150n USB router is a robust, small, low power and reliable router. It
may be flashed from its Chinese firmware to TP-Links 3020 English firmware or DD-WRT or
OpenWRT or OpenWRT based firmwares like Gargoyle and ROOter etc. It is powered by 5 volts and
supports a single 100Mb LAN/WAN port, a USB 2.0 port and a micro USB port for power connection.
The 703n has an internal inverted F ¼ wave length PCB etched antenna. There is no external antenna
connection. This tutorial documents the necessary modifications to add a standard RP-SMA antenna
socket to the 703n. The inspiration for this modification largely comes from these two blog articles:
http://blagg.tadkom.net/2012/09/01/wr-703n-external-antenna-mod-diy/ See comments by luno
http://blagg.tadkom.net/2012/09/15/better-wr703n-antenna-mod/ See comments by Diarmaid Ó Cualain
The 703n’s internal PCB etched antenna is an inverted ¼ wave dipole fed at the 50 ohm impedance point by the PCB tracks. C29, C31 and C32 are a Pi impedance matching circuit.
The PCB tracks are first cut at the on board antenna feed points. The copper track is tinned and the
coaxial cable with RP-SMA connector, soldered to these two points.
Suitable coaxial cable and RP-SMA connectors are readily available. Google “u fl/ IPX to RP SMA male
pigtail cable”. A standard 5/8 wave length router antenna from a Tiny Dovado was used.
I used a basic cheap motorised engraving tool to grind the break in the two tracks.
Cut off the u.fl connector and trim the coaxial cable length accordingly. At 2.4Ghz this cable is quite lossy, so keep it as short as practicable.
The inverted F antenna took to solder like a duck to water as it was not varnished. It was pretty straightforward apart from the scale of things inside the magic little blue box. A jewellers eye piece or similar is essential.
My soldering weapon of choice is an ancient low voltage temperature controlled Weller with a fine tip. Ensure you keep the temperature low, so that you don’t damage and lift the tracks.
I think I have chosen the best location for the antenna, which is adjacent to the existing internal
antenna, but there are a number of options.
There is an amazing reverse engineered circuit diagram of the 703n available on the web:
http://squonk42.github.io/TL-WR703N/
A snap of the WIFI section and the modification follows: