You might want to make a preliminary test of your coax feedline by using an inexpensive volt/ohm meter, checking it on the continuity setting. Disconnect the coax from the antenna and the radio. Place the leads on the inner and outer shield connectors. If you get a meter reading, you have a short
in the feedline and or connectors. Also, use an alligator clip to intentionally short out the inner and outer conductor and test the other end. If you do not get a meter reading, you have an open
contact problem in the feedline. This should help you trace down the problem quickly. If the feedline is the problem, a new antenna will not
help. Until you become experienced at installing coax connectors, buy the coax with the connectors already installed. Don't burn up your transmitter!
get a SWR meter to test your antenna for proper operation and tuning after
you have made sure the feedline is working properly. MFJ makes some inexpensive models that work well.