[Battlemesh] ESD vulnerability with small TP-Link devices modded for ext antenna

[fboehm]

Am 14.01.14 01:11, schrieb Ben West:
> Sorry if this is not directly relevant to Battlemesh.  Sharing, since I
> think some list members are playing around with modded TP-Link devices
> like the TL-MR3020 and TL-WR703N.
>
> I've found, at least for the MR3020, that the popular instructions for
> an external antenna posted online here
> <https://apollo.open-resource.org/lab:argus#modifications> seem to leave
> the device badly vulnerable to ESD damage during thunderstorms.  Two
> MR3020's I'd modded this way (i.e. with a 0ohm resistor de-popped and
> the pigtail attached to an exposed pad) appear to lose ~ 50% of their
> transmit power after a lighting storm passed over.  That is, two
> MR3020's with the same mod and same 7dB dipole, two lightning storms on
> different occasions, and both times the node's transmitter power drops
> substantially at some point during the storm.  In each instance, the
> MR3020 was indoors but close to an exterior window.
>
> Since the instructions for modding the WR703N
> <http://blagg.tadkom.net/2012/09/15/better-wr703n-antenna-mod/> for an
> external antenna are basically the same, I'm guessing this would also
> make that device similarly vulnerable.
>
> My initial hunch that the advertised approach of de-popping a 0ohm
> resistor for the antenna pigtail is bad, because it's removing a filter
> capacitor used for blocking DC (or other unwanted transients) from being
> coupled from the antenna back into the Atheros chipset.  I'm going to
> try severing the trace leading to the onboard patch antenna on an
> undamaged WR703N and solder the pigtail there, as that will at least
> preserve the filter caps TP-Link designed in (at the expense of
> impedance mismatch).
>
> --
> Ben West
> http://gowasabi.net
> ben at gowasabi.net <mailto:ben at gowasabi.net>
> 314-246-9434
>
>
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>

You might have already seen that we grinded down the TL-WR703N PCB to 
finish the reverse engineering of the PCB. I just thought it could be 
helpful for your ESD troubleshooting.

https://forum.openwrt.org/viewtopic.php?id=39829&p=2

Cheers