Have you connected the long wire directly to the centre of the 50ohm coax? If you don't match them with a transformer then the coax cable is just looking like a capacitor shunting all your signals to ground. You'll need a 9:1 un-un up at the end of the wire to the coax.
While, I agree, a 9:1 balun can be used for optimum performance he shouldn't have a problem picking up signals with the center connector hooked directly up to the end of a 70' antenna. Two of my end fed wire antennas work fine this way.
My questions to the op would be:
Did you strip the insulation off of the wire antenna and physically connect it to the coax?
If you did, did you hook it up to the center conductor of the coax or the shield of it or both?
Hooking it up to the center conductor and leaving the shield of the coax open would be proper.
Hooking it up to the shield or both would short it to ground(I had a friend of mine do this).
You also didn't mention what receiver you are using.
If you are using a portable receiver, 70' of antenna could be too much for it, zapping the front end. Some portables have protection for this while others do not.
Jim
Sorry Tom, your post wasn't up when I started posting.