Here is a quote from this thread:
Sound Forum thread about the Audix TM1 / Lectrosonics TM400 kit – RF issue
QUOTE:
Karl Winkler
04-13-2012, 12:02 PM
I know I have asked this before but…. can the TM400 work with an audix TM1 ? or do you still need a small extension cable to break up the RF issue ?
At present, the same problem still exists between the TM1 and the HM transmitter (along with the older UH400TM transmitter). We have reached a standstill mostly because both engineering teams feel that their product is not the issue (ahem…) so yes, a short cable changes the RF properties of the combination so that the problem is reduced to the point where it is usable.
END QUOTE:
It appears that a short XLR cable between the Audix TM1 & the transmitter resolves the issue.