The MR3040 is the natural progression from the WR703 in MiniPwner land, as it is essentially the same hardware but includes a battery in a nice slim package.
There are a couple of guides for external antenna mods on the WR703, but very few for the MR3040. There's a single reference in this forum, but the link no longer works. And some of the guides I've seen involve burning large gaping holes into the body of the router and other nasty things to make everything fit. This isn't a guide as such, rather sharing my experiences (with photos!)
After all, a pocket router with a built in battery and an external antenna is about as good as it gets (without getting properly fancy)
First mistake, and a warning to everyone who wants to try this: Routers seem to use inverted SMA jacks. i.e the pin (male connector) is on the router, whereas most of the SMA jacks you'll find on ebay expect the pin on the antenna side. So if you do what I did, you'll end up with the antenna screwing on like it should, but a female-female connection on the inside which means no connection at all. I ended up stripping a piece of cable and using the core as a makeshift pin. This works well enough if you can get it to stay there. Be warned
This is the connector I got off eBay
I didn't know that it split into two parts, but I'm glad it did because the job would have been far messier otherwise.
The full size thread needed to go into the hole I drilled, with the nut on the inside. However, due to limited space, this was impossible to do. So, since I'd bought two of the connectors, I simply sawed off the end of the thread (the part with the nut) so I was left with a bare thread.
This allowed me to push it in from the outside, and put a regular nut (stolen from the other connector) on once it was in, and the smaller SMA jack had been screwed in.
The two connectors, before sawing:
The second challenge was mainly due to the fact that I chose to put the antenna in the middle. I could have (maybe) avoided this, but it makes more sense to put it in the middle and it was doable.
The shielded part of the connector is very inflexible for the first few mm. This forces it back into the plastic, so I needed to cut another hole:
This allowed it to fit nicely, and once the case was closed, the battery fitted perfectly without any visible plastic damage or bulging. The only downside is that it takes up some of the space needed to get the battery out, but it doesn't make any difference.
The actual connection to the board is nice and simple. Desolder J1, solder the core to the side of J1 nearest L15 and solder the shield to the nearby ground point. I left a bit of slack for future maintenance purposes, also because it fits fine.
The finished product:
Performance wise, without anything connected to the SMA jack, it is comparable to the built-in antenna. So if you don't want to use the external antenna, you don't have to. If you do use it, then it gets about the same range and my WR741 desktop router.
Haven't found a nice way of properly testing range, so if anyone has any suggestions, or would like to know...
But it definitely makes a difference. And looks pretty cool.
Feel free to ask questions or make suggestions for future mods.
All images link to higher res versions, if you want to take a closer look.