Quote:
Originally Posted by Rnovrit
True on both accounts Jollymon and Curr. I added a roll of 1" copper tape (think Faraday cage) to my order to add a second layer to help prevent any signal from pushing through. Hope this all works.
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Stop the presses, copper tape probably not a good solution... read on.
Quote:
Originally Posted by jollymon
If you have a correctly designed/made 50ohm termination (and the cable/adapter to it as well) it WILL NOT radiate. If either the coax cable, connectors, or 50ohm termination are not correctly made, it will radiate a little as mentioned above.
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Ok, so I just spoke to an expert, and if you don't want to believe me, that's cool, but I know what I don't know, but I do know who to ask. This guy is "the guy" in our division (very large company, aerospace and defense sector). Patent holder, innovator in inertial guidance and telemetrics, and currently working on a lot of next-generation stuff that the "prime" defense contracting companies are very interested in. He's the real deal. Yes, I'm being purposely vague.
That said, the trace from the signal source, to the end of the PCB still counts as an antenna, and will absolutely radiate signal even "correctly terminated" (which we are just assuming it's 50 ohms...) which is probably why gatormaro saw limited connections occasionally.
He said that copper tape / shielding may not be a great idea due to it could actually increase the radiation pattern (my words mangling his explanation) and might not attenuate it at all. He explained to me some examples of antennas he'd built using layering of copper which helped propagate the waves instead of attenuate them.
Eccosorb, an very common energy isolation barrier, is perfect for this type of thing.
He also said, without looking at the board, in general, a good idea could be just AC coupling the signal to ground at it's origin, and at the edge of the pcb with something like 100pF to 1000pF cap.
So once I pull this thing and see what kind of space I have to play with, I'll have a better idea of what I'm going to try. But we have a tons of Eccosorb at work that I can probably snag some to try out.