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Grounding a TEM Cell
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Hi to all.
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Right now I'm using TinySA Ultra for conducting some test in order to reduce some harmonics around 700Mhz on my product.
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The issue is that the TBTC2 tem cell is able to catch a lot of interference in the area where I live. Everything is floating since the product is battery powered and the TEM Cell ground is connected to the shield of coax cable up to TinySA (used not connected to PC).
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Maybe grounding everything to the house earth could be a good or a terrible wrong idea?
It could help? The conductive tent is a must?
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Can you help me in this?
Thanks
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NH |
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On Tue, Jan 21, 2025 at 05:03 PM, <nighthawk.eng@...> wrote:
With things like that the only way to know is to try.? Some electronics instruments (my RF RMS voltmeter for one) and musical instrument amplifiers have a switch which allows floating or grounded use.? A conductive tent or screened/shielded room will likely help and is unlikely to hurt.? Turn your cell phones off/keep them at a distance.
Best regards, Don? |
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On Tue, Jan 21, 2025 at 02:03 PM, <nighthawk.eng@...> wrote:
A TEM cell acts like a terminated shielded cable with the device under test between the shield of the cable.? An enclosed TEM Cell or GTEM can be used in a noisy environment as long as it has proper power and cable filtering.
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The TBTC2 is a stripline TEM cell with open sides and cannot be used effectively in an environment with high ambient for radiated emissions testing.? For high ambient environments, it needs to be located in either a shielded enclosure or conductive tent, neither of which is cheap.??
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E-Field and H-Field probes are another option for locating troublesome emissions, especially at 700 MHz.? If you see a 20 dB reduction in levels with the probe, you will see about the same reduction during compliance testing.? Just be careful to rescan the entire frequency range after any EMI fix.? Fixing one frequency can sometimes be detrimental to other frequencies.
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Herb
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The TEM cell should be a completely closed Faraday volume.? If it maintains its "new" integrity, there should be nothing leaking into the volume. I've used a TEM cell some 500-feet from a major cell tower.? I can not detect the emissions from that tower with nothing in the cell and with the cell completely closed.? Further, a major compliance lab. is located roughly 2-blocks from the location of the TEM cell and the chambers leak just a bit of the cell tower emissions.? "Grounding" is often thrown around as a solution to everything bad with RF.? It seldom solves anything!? With absolutely nothing in your TEM cell and the cell closed, what does the spectrum show when connected to the SA?? With the SA outside the TEM cell or the cell open, do you detect any emissions around 700 MHz?? What is the quality of the coaxial cable connecting the TEM cell to the SA?? Of course, lots of other questions, but that should do as a starter. Dave - W?LEV On Tue, Jan 21, 2025 at 10:03?PM nighthawk.eng via <nighthawk.eng=[email protected]> wrote:
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Dave - W?LEV |
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On Wed, Jan 22, 2025 at 10:11 AM, W0LEV wrote:
Dave,
? ?The original poster stated that he is using a TEKBOX TBTC2 TEM cell which is not an enclosed TEM cell.? Our lab referred to that type of TEM cell construction as a Triplate or Strip Line device.? The sides are completely open and therefore the device is susceptible to environmental ambient when not used in a shielded enclosure.
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?Herb
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OK.? Even I've used that sort of TEM cell.? Thanks for the cliarficatin.? I did not read the original posting if I even received it...?? Thanks, again. Dave - W?LEV On Wed, Jan 22, 2025 at 6:36?PM hwalker via <herbwalker2476=[email protected]> wrote:
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Dave - W?LEV |
Donald S Brant Jr
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