Actually it's not standard Pipe Thread. I wish it where. It's a special thread sized used for Marine Radio Antennas.
If you want to get the EXACT size thread count of 14/inch then go with the Marine Stuff Below. You can jerry rig it maybe but it would not fit exactly. Believe me as I tried to do this and could not get it to work properly. I wish I were wrong as I could have saved myself $100 bucks on this project.
If you get the proper sized threads then you can screw it apart later on without doing any damage to the expensive PLASTIC threads on the Humminbird GPS Puck Base. If you were to screw the GPS Puck Antenna onto a standard pipe thread that's close in size but not an exact fit you will Certainly damage the fragil plastic thread inside the GPS Puck base. Female part of the GPS Puck Base.
I would rather just use sheet metal screws and screw the GPS Antenna TOP part of the puck onto the flat metal boat deck on my Fishermarine Aluminum Bass Boat than to ruin the plastic threads on the GPS Antenna Puck Base.
NOTE: The GPS Accuracy seemed to me to be the same whether the puck was flat on the deck or rasied up 2ft high above the deck of the boat. Each position gave me the same estimated accuracy this spring when I did this project.
NOTE 2: This Oct the GPS accuracy has improved greatly. I am getting estimated accuracy of plus or minus 4 ft now.
You can order these from Westmarine
Stainless Steel Pedestal Mount Model # 409888 for $22.49
Shakespeare Antenna Extension - 2 FT Galaxy Model # 329724 for $57.99
Also Ram Mounts has a RAM-112U UNPKD RAM MOUNT W/ 1"-14 Threads.
I have all three but am not using the Ram Mount at this time. I used the WestMarine parts on my boat.
With the Humminbird GPS Antenna puck sticking up about 2ft 4" above my boat deck the puck is now above the motor cowing and can clearly see 360 deg around the sky.
Check out www.westmarine.com
Your local hardware store should carry stuff like this, it is just a standard pipe thread.
Depending if you want plastic or galvinized steel, I would look in the plumbing section.