After some trial and error with my previous callers, I rebuilt from the ground up. This time using a Pelican case 1150 which gave me extra room, I can carry all the components, including my MP3 player, Azden transmitter and spare batteries in one case. I used a Speco8 horn, a Velleman 7watt mono amp (much better no hiss then the radio shack AMP). I modified the Azden reciever so it and the AMP can be powered from a 9.6 volt RC battery pack for longer calling times. I am able to get 75 yards of range with the Azden keeping the antenna enclosed inside the case.