Car Alarms: Jammed Frequencies?, vehicle security system, alarmtek

Question
I am a sound engineer for a local bar, and we have had many complaints from
customers about their car alarm key pads not working properly out in the
parking lot, from my understanding these units operate in a range of 300 to
400 mhz.  What would jam this frequency?  What can unjam it?  For some
background I can state, I run a wireless mic, flawless, Wi fi, no issues, wirless
dj lighting, no problem, and a rf universal remote, works great.  Step outside
the bldg, and not a single car alarm keypad works until it is right on top of
the vehicle it operates.  Usually needs to actually touch the vehicle some have
said.

Answer
Do not think it has anything to do with the electronics in the bar.  It is probably RF from a radio tower or cell tower or similar, have any AM radio stations near by?  The equipment referenced in this question typically operates in a different frequency range than that of a vehicle security system.  I wish I could offer assistance but without someone being there with the proper equipment I would only be able to guess at what the problem is.

Regards,
T.V.-ALARMTEK ADVISOR