Do you have to dump hex in it. Like the old Motorola and Intel formats? In the old days we made the obj/binary file, then had to bin2hex (convert it to a formatted ascii file with address, byte count, bytes and checksum) and transmit it in ASCII to the loader.
You really should look into the PICs, a lot more fun and a lot less money and headache.
Is your Z80 talking to the PC OK and you just can bot get your code loaded? Hyperterm is the worst dumb terminal program, maybe get procom or something else. Where are you getting stuck. Any info on the loader?