The formula to get the DME(VOR) frequency from a TACAN channel is the following:
There are two 'keynumbers' - 1063 and 1053 - which you have to add to the TACAN channel to get the DME frequency.
Up to channel 59 you have to add 1063.
From channes 70 on you have to add 1053.
Example:
TACAN channel is 44:
44 + 1063 = 1107 = 110.7MHz
TACAN channel is 98:
98 + 1053 = 1151 = 115.1MHz.
Should be quite easy with this formula.
DBate