Put it in a box!

After buying the budget RTL-SDR I decided that I needed to go lower. The Nooelect upconvertor was just a bare board though, and the adapters and cables started to piss me off almost immediately.

USB->RTL->upconvertor->antenna, plus another USB to power the upconvertor. Just didn’t seem right. Also it was obvious running the setup anywhere near my computer resulted in tons of wideband noise being picked up.

So I bought a Hammond project box and stuffed it all in there.

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As you can see, instead of using connectors, I pulled the RTL USB connector off, as well as the SMA connectors on the upconvertor board and wired it up directly. Instead of an SMA antenna input, I switched to BNC which matches more of my stuff, and wired a panel mount to the upconverter board.

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The USB connection was the uglyest:

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I originally intended to solder directly to the leads on the RTL USB connector, but that didn’t work out very well, so I pulled the connector off completely. You’ll also see a small toroidal choke that I ran the cable through which was recommended to limit the harmonics from the digital signal I assume. I put it inside to be clean, but I’m wondering if it would work better if I kept it outside the case. I can use a clamp on choke outside as well I suppose.

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Since the RTL board didn’t have any mounting holes I just used half of the clamshell case to cradle it, and mounted that to the case with a single standoff.

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Overall I think it looks okay, and is much more functional. I’ll post some screenshots of spectrum once I test it connected to an antenna.

References:

Hammond Box: 1550B I think. 

Choke: http://www.amazon.com/dp/B009N83WFK/ref=pe_175190_21431760_3p_M3T1_ST1_dp_1

BNC Panel Mount: http://www.amazon.com/gp/product/B00AUB5X2Y/ref=oh_details_o09_s00_i00?ie=UTF8&psc=1

USB Pinout: http://pinouts.ru/Slots/USB_pinout.shtml

 

 

 

10 thoughts on “Put it in a box!

  1. Looks awesome.  I had modified an old KVM case to hold the hamitup, but the cable mess is driving me nuts as well. I now have a weekend project. Excellent write up.Did you get much improvement in RF noise?

    • So far no. I also moved location to my office in an industrial park, so I’m not clear if thats the issue or if it’s something I did wrong. But right now I’m not receiving any signals below about 100mhz either, so I assume its a construction issue.

  2. Thanks Matt. I only did a base signal test before I had to put it aside for a few days to do things that make me money. 

    Wednesday I’ll be running on air tests and see how well it does. Everyone else that I’ve read who has put these in shielded boxes has seen an improvement, and I can’t see that it wouldn’t offer at least some improvement. 
    I have high hopes. 
  3. Just out of curiousity, how are you grounding the boards? I have my dongle shielded in an aluminum box and grounded to chassis then I ran some copper braid to a spare ground rod and that really cut down the noise.I just got the up-converter and I haven’t gotten a chance to build an enclosure for it as of yet but with just dongle shielded and grounded it has been silent on the emi/rfi noise front while running the up-converter.As Erixxx mentioned it couldn’t hurt to put one or two snap-on chokes on the USB connection outside of the box. Also shielded USB cables cut down a lot of noise.

  4. Currently I just have the chassis ground like you mention. I haven’t tried a real ground, which of course makes sense now that you mention it. 

    I tried the chokes outside the box, and didn’t notice a difference unfortunately. USB cables are required to be shielded by spec, but often the shielding is questionable. This one I have seems pretty good, but not a double-layer. 

    Micah
  5. I don’t know if you have gotten the noise issue resolved yet, but here is what I did with my first RTL-SDR and it helped a TON with the noise.One of the problems we have with noise is the usb cable itself. A lot of problems are caused because the USB Gnd and USB shield end up connected at the USB connector itself. Because you have soldered yours directly to the board you do not have this issue.However, one of the things you will want to do is connect the USB shield, that is currently connected to nothing, to the Case itself. This will allow any connected cables to pass the shield through the sdr case back to the USB sheild and to the computers ground. I did this when I created my SDR shielding case. Without the USB shield connected to the case the noise was almost the same as before, with it connected the noise floor dropped significantly. You might want to peel back the casing on the USB cable, tape the shield to the side, and close the top to check out how that changes the noise levels.I also live within 1 mile of 2 FM transmitters and they are brutal to my RTL-SDRs sensitivity. I bought a $5 FM trap from radio shack and connected it. It is not an amazing performer, but it does a good enough job attenuating the nearby FM and keeping it out of the other bands, especially 10m and 6m HAM (this sdr doesn’t have the upconverter on it.)Anyway, I hope that helps. I actually came here to ask if you could measure your enclosure for me? I am going to be building another SDR case with a ham it upconverter included this time and wanted to order something similar.Try the Grounded shield out I’m sure you will be amazed at the difference.-BJ  

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