Planning to install an NMO mount on my truck roof for a Larsen 2/70B antenna. I've read conflicting information about the proper hole size - some say 3/4", others say 19/32". What's the correct drill bit size for a standard NMO mount? Also looking for advice on proper sealing techniques to prevent water intrusion. The truck will see daily use including car washes, so waterproofing is critical. Should I use butyl tape, marine sealant, or both?

3/4" is correct for most NMO mounts. Use a uni-bit or step drill to avoid tearing the metal. For sealing, I use butyl tape under the mount plus a bead of marine sealant around the base.

Been installing mobile antennas for 20 years - definitely 3/4" hole. The Larsen 2/70B is an excellent choice, very rugged. Don't forget to treat the exposed metal with primer to prevent rust.

New ham here - what's the advantage of NMO over magnetic mount? I've been using a mag mount Diamond but wondering if I should upgrade to something permanent.