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I have encountered a situation in my RF coordination that seems just at the edge of my knowledge and I'm hoping some of the Lectrosonics RF gurus that frequent the forum can chime in on whether I'm understanding the situation correctly. And whether I should be concerned. I'll try to be succinct but this might be a bit long, sorry. What sparked the question is this: I use Shure's Wireless Workbench software to calculate coordinated frequency sets for the various wireless systems used on our campus. A portion of that equipment is Lectrosonics, and I can connect to that equipment for monitoring with Lectrosonics' Wireless Designer software. I ran into a situation where the Lectrosonics software is complaining about frequencies that the Shure software says is fine. The specific complaint Lectrosonics Wireless Designer has is: "The System at 475.300 MHz is subject to interference from 3rd Order IMD at 475.175 MHz caused by the mixing of carriers from transmitters at 532.700 and 590.225 MHz. The offending carriers do not all fall within the passband of the affected receiver." On the other hand, the Shure software is not complaining. Both programs are configured to flag 2Tx 3rd Order intermod products that fall within 149kHz of carriers - and I can do the math myself to see that this potential intermod product fails to meet the spec. So I am wondering why Shure Wireless Workbench would not flag it. The only reason I can come up with why the Shure Wireless Workbench software might not be flagging this as a problem is that it has a "Filter Selectivity" parameter (which I have left set to its default of +-50MHz outside the tuning range of the receiver). It seems that the Shure software is predicting that the 532.700 and 590.225 carriers will be filtered out by the receiver front end before they can intermodulate and create a problem. This seems to be the basic idea of the Lectrosonics software's message about the carriers not falling within the passband of the receiver. But that's not the only way this intermod product can be a problem, is it? For example couldn't it be created by transmitters in close proximity to each other or by strong signals in a multicoupler upstream of the receiver? Am I being paranoid or should I legitimately distrust the Shure software because of this?