Wow! I've never seen a Hyundai remote even approach 100 feet before. It's
usually about 50 feet, tops, with an advertised range of 25 feet. Most
other manufacturers I've seen advertise the 50 foot range.
Obviously, the more powerful the transmitter, the better the range. Some
transmitters use two 3V batteries instead of one. I haven't opened one of
the newer-model remotes, so I don't know whether that's the case with them.
If you're in an area with strong rf signals, then you're more prone to
interference. I saw some poor technician try to diagnose a customer's
intermittently inoperative keyless entry over about three or four service
visits until he happend upon some papers under one of the seats with a
television station's letterhead. Turns out the problem only ever occurred
at work. Whaddaya know? I've heard some stories that there are areas in
southern Maryland where car remotes won't work for a few days. I'd
suspect this may be related to military testing. There were verified news
reports of people's garage door openers not working in Frederick, MD due to
military operations at Fort Detrick. Bottom line, these frequencies were
intended for military use, and these devices are simply allowed to borrow
the frequency when the military is not using it. The devices just operate
at a low enough power that they aren't strong enough to interfere with the
military uses of the frequency.