I recently demolished my EW100 G2 transmistter and was looking for a replacemet for it. I found a SK 100 G3 A 100 transmitter on Ebay. Can I use the two together, provided they're on the same frequencies?
As long as your receiver is in the same frequency block, yes, G2 and G3 are compatible. Not only does Sennheiser claim this, but I've actually done it. G3's have a few extra frequencies that your G2 won't be able to tune in, on both the upper and lower end of the frequency range (I think), but all the G2 frequencies should be in the G3.
Proving the frequency is the same G1, G2, G3 and 2000 series are all fully compatible with each other.
The only thing to watch is if you use an old G1 transmitter with a later series receiver - if you do you have to switch *off* the pilot in the receiver if the transmitter is a G1.