Not moving, Rather spread out, akin to a fully deviated FM signal. Presuming highly linear gain stages, if there is any mixing of of signals, it will result in an overall rise in the noise floor, not defined carriers experienced with typical FM systems.
That was my understanding also, and what I would expect: a raise in the noise floor... but upon measurement, and as the scans/screenshots show, you can see defined carriers caused from the digital transmitters in close proximity.
At 20mW (true, in a low ceiling, very bunker-like stretch of a warehouse) it does seem to me the power of the IMD products can't be disregarded, and the equipment profile in WWB6 for Axient Digital (ULXD and QLXD also) does disregard IMD, at least in the "more frequencies" scheme. Having 4 Tx as close as I did aren't common practice fortunately.
That is correct, Sennheiser 6000 series is 'intermodulation free' because of extremely linear rf amps and the use of rf isolators in all transmitters.
I'm not absolutely sure whether the Shure Axient Digital is also using isolators, but I don't think they have them...
This makes sense... circulators probabilly are key to their design.
The quick test I did was a worst case scenario with the packs as close together as they could get. The next question would be does it affect rf performance. In the case of the AD the answer is no. If someone around the Detroit area has a 6000 series available I would be more than happy to do a direct A/B comparison.
During my tests, while producing intermod at a given frequency and then firing the transmitter allocatted to that same frequency didn't seem to impact the audio/link-quality. Receiver still reported 5 stars quality and sounded good. Range would still be an issue of course... I get the part where physics are still physics