Posted: 12/3/2016 4:15:06 PM EDT
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Recently I grabbed up a used Dell e6410 as a shack laptop. As many others I had a few rtl-sdr dongles lying around, and one was always lodged in my docking station, but I didn't always have one with me when taking the laptop out and about. Since I wanted to make it as easy as possible to have a rtlsdr receiver available I figured an internal solution would be best.
I started looking for an internal pcie rtl-sdr card as the e6410 had a open slot designed for a factory LTE card option. After some hunting I found that such a beast did not exist. What I did find was a inexpensive pcie usb2 controller card. This little $3 card allows you to directly plug in a small usb dongle and mount it in a pcie slot. Eyeballing the size, I figured a rtl-sdr nano2 would fit perfectly, so I purchased both. Once both items arrived I tore the rtlsdr nano2 out of it's case and fitted it easily within the pcie/usb card. After dropping it in the open slot and booting up the system this device posted as a usb controller and I could find the dongle within dmesg and lsusb. The next hurdle was how to get an external antenna configured with this thing... 
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Working through the antenna problem I realized that the e6410 is just old enough to still have a external space allocated for an RJ11 jack. Upon further inspection via a handy teardown site I found the the RJ11 jack was pretty close to the internal channel for the existing antenna wires for the wifi and optional LTE card. Based on that it made for the perfect candidate for being repurposed.
Considering the size of the hole, I figured an SMA connector would be a good fit, and I would pass it directly through the RJ11 jack once I "dismantled" it. Since I wanted to be able to easily dismantle the setup if parts needed to be replaced, I decided that I would need an MCX to SMA cable setup, as opposed to directly soldering the cable to the rtl-sdr dongle. When looking at the space around the dongle, it was decided a 90 degree MCX connector would be needed if there was a chance to get things crammed in. 
I had determined that the internal channel for the wifi and wan antennas would serve as my route for this new antenna cable as well. Realizing space is at a premium it was also determined that I would have to tear out the LTE wan antenna to make room. Following the aformentioned teardown of rhte e6410, this was pretty easy. 
After measuring the distance from the RJ11 jack to the pcie card I figured a 16" cable would do the trick, and purchased a premade MCX to SMA flange mount cable made from RG316 to complete the job. Once I fitted everything there were a few hitches. 1) The RG316 though well insulated, is way to fat. I'd need something thinner. 2) The flange mount, though a good match for size to the RJ11 jack, would now screw down into....what?...for support. Based on this I went back to the drawing board on cable options... |
In shopping for a new cable option I ended up going directly to the vendor who provided my RG316 cable, and found they had a "custom" option. Since they would build anything based on what they had I opted for another 90 degree MCX to SMA cable but constructed of 1.37mm cable, which is the same cable used for some of the wan/wifi antennas already in the machine. Also instead of an SMA flange connector I opted for a long SMA bulkhead connector to directly pass through the channel of the RJ11 jack.
Fitting this assembly I found it required a bit of trial and error to allow the SMA connector to not abut the USB sockets on the motherboard. Once the sweet spot was figured out, I tightened things down and filled the hollowed out RJ11 jack with sugru for support. 
After the new connector had dried I was easily able to fit the assembly within the provided cable channels with one complication. The only good path to this channel required that I cut a notch into the chassis of the laptop. I blocked off the area with some painters tape, and using a triangular file proceeded to cut a notch of the required size to allow safe passage of the 1.37mm cable. 
Once it was basically assembled I found that I had a bit of extra slack in the line, but this fit into the general area where the RAM was located. A few final cables were re-run and hooked up to the wifi, the system was buttoned up, and we had a nice neat looking (though slightly long) SMA connector peaking out from our RJ11 spot. All in all it seems to be working pretty well. 
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Very good project!
I get to use some of the Epiq receivers that are very similar. It really is a great design. Some get really concerned with RFI/EMI because they are so close to the electronics of the laptop. If that happens then try and do some copper foil shielding. Do you think there is enough room for an airspy mini? |
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Quoted:
Very good project! I get to use some of the Epiq receivers that are very similar. It really is a great design. Some get really concerned with RFI/EMI because they are so close to the electronics of the laptop. If that happens then try and do some copper foil shielding. Do you think there is enough room for an airspy mini? So far I haven't noticed a huge difference in the noise floor, but haven't really done a direct comparison between the internal card and an external shielded dongle. I had come to the same conclusion on shielding, and will probably wrap it up anyway. Considering the nano has a small amount of wiggle room, I guess the airspy is a no go. Since the pcie adapter is $3, if someone has an airspy it's certainly worth a try. |
Looks like I got excited and posted before all the pictures were uploaded. I think width wise the mini will fit but the slot location will depend on if it fits. My think pads have the slot in the middle of the motherboard. Like this one.
I am really excited to see how it turns out. If I can do anything to help let me know. |
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Cool project! That really turned out nice. I would add a small piece of kydex or ABS to the bottom of the laptop with some 3M double stick tape that extends out past the SMA connector to give it a little protection from bumps.
That would be really cool to have sdr always available. |