International Radio :: Products by radio :: Drake :: R-4C
#2611.1/#2612.1 (also known as GUF-1) are superior replacements for original 4-pole units. Exceptional improvement. Installation requires drilling three small holes in the radio chassis -- instructions are provided.
The 2nd IF fitlers are designed to be installed in the accessory crystal filter slots. Installation is as described in the Drake Model R-4C Receiver Instruction Manual.