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Item Description
Price (Amazon)
Link (Amazon)Price (Ebay)Link (Ebay)NotesSparkfunPimoroniAdafruit
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MUST HAVE
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TinyFPGA Bx$42
https://smile.amazon.com/TinyFPGA-MMP-0319-BX-Without-Pins/dp/B07HCXTNFX/ref=sr_1_1?dchild=1&keywords=tinyfpga&qid=1600737536&sr=8-1
$56https://www.ebay.com/itm/TinyFPGA-BX-Board/233104216995?hash=item36461813a3:g:RBYAAOSwZu9faNL-This is the "device under test." We'll load a firmware that makes some high-speed signals on some GPIO pins that cause us to "fail EMC testing." While we could apply the techniques of this workshop to ANY board including Arduino, and (kind of) any frequency range, these cheap RTL-SDRs we're planning to use only tune as low as 25MHz, so we need to have a known signal we can control above that frequency. An FPGA with a PLL is the most practical off-the-shelf answer. If it works out that you CANNOT find one of these, we CAN make due with whatever board you can get your hands on, and sniff around it to reveal what kind of noise it emits and why. A USB hub would be a great choice, especially with the SDR itself plugged in to constantly exercise it. But you have to be able to take the case off.
https://www.sparkfun.com/products/14829
https://shop.pimoroni.com/products/tinyfpga-bx
https://www.adafruit.com/product/4038
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RTL-SDR: Nooelec SmarTee (integrated bias tee)$32
https://smile.amazon.com/NooElec-NESDR-SMArTee-SDR-R820T2-Based/dp/B079C3FHPG/ref=sr_1_1?dchild=1&keywords=smartee&qid=1600733852&sr=8-1
$32https://www.ebay.com/itm/NESDR-SMArt-Premium-USB-RTL-SDR-w-0-5PPM-TCXO-Metal-Case-SMA-R820T2-RTL2832U/162132282077?epid=4011032708&hash=item25bfd64add:g:I20AAOSwzJ5XbKyzAny RTL-SDR will do, as long as you can wire it to a LNA (which will have Female SMA connectors). RTL-SDR is the cheapest and most ubiquitous option. This one has a "Bias Tee" which puts 5V DC on the input to power an attached LNA. The LNA specified below can be powered by this bias tee. It can also be powered by a USB micro-B cable if you use a different RTL-SDR without one. There are cheaper RTL-SDRs, but they usually don't have SMA connectors so you'd be on your own for cabling, and adapters kinda make up the cost difference. Software used in the workshop will also be broadly compatible with most SDRs if you already have one, including the HackRF (which works SUPER well), or the LimeSDR (which works great but can be a pain to set up).
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Low Noise Amplifier: Nooelec Lana$20
https://smile.amazon.com/Nooelec-Lana-Barebones-20MHz-4000MHz-Capability/dp/B07XNH6QW6/ref=sr_1_8?dchild=1&keywords=nooelec+LNA&qid=1600734073&sr=8-8
$27https://www.ebay.com/itm/Nooelec-Lana-Barebones-Ultra-Low-Noise-Amplifier-Lna-Module-For-Rf-Softwar/143560803514?hash=item216ce404ba:g:5iIAAOSwwYledZpWYou NEED a low noise amplifier to boost the pittance of a signal our antennas will generate. This one is about 2x as expensive as the cheapest options, but works well at 5V (which is easier to source than 12V) and can be powered by the SDR itself using the one above, or a cell phone charger otherwise. I've had good luck with cheap LNAs like like this one linked to the right, but you HAVE to power them from 12V to get good gain, and a 12V adapter brings the cost up to ~$20 anyway. In theory, the 12V LNA to the right has better gain than this one, but in practice for our frequency range, I don't think that's actually true. This one feels much higher quality, in general. Be aware that if you DO pick a different, cheaper LNA, most have a DC blocking cap on the output and WON'T be powered by a bias tee without modification. It's also tough to know for sure whether any given LNA will work well at your particular bias tee voltage. I do know this combination DOES work nicely.Cheap 12V LNA
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SMA M-M Cable X2 (amz. link is a 2-pack)$9
https://smile.amazon.com/WayinTop-Antenna-Extension-Coaxial-External/dp/B0828R8Q47/ref=sr_1_19?dchild=1&keywords=SMA+cable&qid=1600734148&sr=8-19
$5.60https://www.ebay.com/itm/SMA-Male-To-SMA-male-plug-connector-lot-Jumper-Coaxial-RG316-extension-cable/202144321942?hash=item2f10bd9196:g:p4gAAOSwzotcymDSAny SMA cable will work here, but you need two: SDR<>LNA and LNA<>probe. Longer is just easier to work with. Cheaper if you order from China, but you probably don't have time for that gamble.
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SMA Female panel-mount jack$7.80
https://smile.amazon.com/Female-Socket-Mount-Adapter-Connectors/dp/B07QH6TWRY/ref=sr_1_3?dchild=1&keywords=sma+jack&qid=1600735033&sr=8-3
$4https://www.ebay.com/itm/Connector-SMA-SMB-male-plug-female-jack-solder-PCB-Panel-mount-Bulkhead-Flange/113888897599?hash=item1a844eaa3f:g:1AAAAOSwKeNds-~JSMA female jacks to use for our probes. You only NEED two, but the more you get the more probes you can try making. Again, China is cheaper but riskier. You could always solder directly to butchered SMA cable too, but I don't advise it.
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Magnet Wire (30AWG enameled wire recommended)$7.20
https://smile.amazon.com/BNTECHGO-AWG-Magnet-Wire-Transformers/dp/B07GBMKMKY/ref=sr_1_3?dchild=1&keywords=magnet+wire+30+gauge&qid=1600735493&sr=8-3
$7.20https://www.ebay.com/itm/30-AWG-Gauge-Enameled-Copper-Magnet-Wire-2-oz-402-Length-0-0108-155C-Red/371713037529?epid=1080655887&hash=item568bd2d4d9:g:CbYAAOSwMmBVw6n~You need really very little of this, so if you can repurpose wire you already have, that's ideal. Finer is better down to about 30AWG so we can make really small loops. Similarly, enamel insulation is probably a must. Worst case, you CAN get away with any old wire. Wire wrap wire works pretty well.
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Safety pin, or something like it.$0We'll be winding our finest H-field probe on the smallest stiff needle you have. Ideally you want something in the 0.5mm range, stiff enough to wrap a turn of magnet wire around tightly. A male header pin would work, or maybe a short component lead. I used a safety pin, and managed to stab myself with it rather hard, in most ironic fashion.
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Wooden skewers, or something like it$0Not strictly necessary, but probes made out of strands of 30gauge wire are quite floppy. I used some wooden skewers and tape to make mine easier to handle.
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Kapton tape, or hot glue, or etc.$0Something to attach your probe to your skewer. I used kapton tape; hot glue would be better.
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Larger cylindrical objects for winding probes$0We'll wind other H-field probes on larger things in the 1mm to 20mm range, whatever you've got handy.
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$118
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Fun to have (NOT critical)
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Copper shielding tape$11
https://smile.amazon.com/LOVIMAG-Conductive-Shielding-Repellent-Electrical/dp/B071JKLFXX/ref=sxts_sxwds-bia-wc-p13n1_0?cv_ct_cx=copper+shielding+tape&dchild=1&keywords=copper+shielding+tape&pd_rd_i=B071JKLFXX&pd_rd_r=f9bc434d-99e9-4bfa-8f2a-ff15a5f08188&pd_rd_w=MwjtD&pd_rd_wg=Jd4qr&pf_rd_p=42e41e42-79c0-42f8-8a91-d71b944e9fa8&pf_rd_r=47Y87WK3Y3M6W3JB0G8A&psc=1&qid=1600737021&sr=1-1-791c2399-d602-4248-afbb-8a79de2d236f
In theory, our probes need a ground shield around them to avoid picking up E (electric) field signals as well as the target H (magnetic) field signals. In practice, I've found that unshielded probes perform adequately, but there's always playing around to be done.
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Fabric shielding tape$12
https://smile.amazon.com/Conductive-Fabric-Adhesive-Laptop-Shielding/dp/B019OTRL5O/ref=sr_1_6?dchild=1&keywords=shielding%2Bfabric%2Btape&qid=1600737138&sr=8-6&th=1
This serves the exact same purpose as the copper tape, but looks and feels cooler.
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Shielding paint$52
https://smile.amazon.com/gp/product/B01M3U66XN/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1
Wrapping your probes in tape-as-shielding works, but it's hard to get good quality and hand feel that way, since you want the probe RIGHT UP AGAINST the trace in the case of the smallest probe. I haven't built probes this way yet, but the theory is to 1) make the probe with magnet wire, 2) insulate the feed line joint with plastidip 3) dip the whole thing in this as a shield 4) another layer of plastidip. We'll see if that works. Follow along with me if you like, but ONLY if you want to spend too much money for science.
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PlastiDip$10
https://smile.amazon.com/Performix-075815116048-Blue-Plasti-Dip/dp/B000HE9T6A/ref=sr_1_6?dchild=1&keywords=plasti+dip&qid=1600737215&sr=8-6
See above for super-cool-pretty-probes-that-don't-work-measurably-better.
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