I found this great little site for calculating the materials and measurements for making a great copper j-pole antenna! If you were looking at making one of these classics, this will help you out !
J-Pole Antenna Calculator
The Frequency you entered: 146.94 MHz
Measurements(95% Velocity Factor for Copper Pipe):
A: 1.454 meters or 4 Feet 9.24 inches
B: 0.485 meters or 1 Feet 7.092 inches
C: 0.049 meters or 0 Feet 1.932 inches*
D: 0.046 meters or 0 Feet 1.812 inches §
* Adjust up or down to get the best SWR.
§ Measurement not critical.