6U8 or 6X8 are a dime a dozen and great mixers. Also 6BL8, 6EA8 are good
up to 220MHz. 6J6 goes to 600MHz.

I have tried to develop "glass Gilberts", but tubes are too linear.

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca