Autopage 650 Antenna help

Hey guys, I am a newbie here.  I have installed a few alarms / remote starts... 6 to be exact.  Anyways, I got lazy and let my local shop do it.  Everything works great with it except the antenna.  The second day the alarm was installed, the antenna just was horrible (had to be at the windshield with the transmitter to disarm, etc).  Now, I took the antenna to this weird electronics guy, and he "fixed it" but every now and then it acts up.  I am wondering what I am supposed to do about this.  Sometimes it works from like a block and sometimes 3 feet.  I reprogrammed both transmitters already, so I know thats not the problem.  My local shop said that AutoPage made crappy antennas for the 610 and 650 and that they eventually said screw it and started putting antennas from the 750 in place.  That causes the alarm to work from like 5 blocks, no lie.  So I guess I am wondering what antenna (from a different alarm or something) I can use in mine's place.  According to Autopage, the antenna for the 750 is a 2 way antenna and thats the only difference... but come on... its still a 3 pin connector.  I don't know.  If anyone has suggestions or has dealt with this before... please please help me out.

~~~~If you got this far, thanks a ton for reading! 

Help me!!!  Someone!  AutoPage sucks for customer service, and they already gave me a replacement 650 antenna at my local shop.

~Bob