I just picked up some fine looking heavily built male N connectors at a hamfest. Before I mount one onto the antenna end of a cable and send it up 18 feet over my roof I'd like to make sure it's a 50 ohm "N". Does someone know how to tell a 50 ohm from a 75 ohm "N"? Thanks in advance for your help. 73, Lenny W2BVH