Topband: problems with RFID-key-cards / transponder door locks in Hotels ?

[GeorgeWallner]

Tom,

The technology you are talking about is called NFC, Near 
Field Communications. It uses the magnetic (H) part of the 
RF radiation -- near field -- but it does have an electric 
component, although that is quite weak. The antenna, both 
in the lock and in the card, is usually a multi-turn loop. 
The lock transmits power which is picked up by the card's 
antenna and is used for powering the chip and 
communications. Most systems use a rolling code, which 
provides security and protection against interference.

It is not likely that your transmissions (even on 14 MHz) 
will trick the locks to open. It is more likely that 
during transmissions locks may not open, or open 
sluggishly. You may also get some noise on 20 meters from 
the side-bands of 13.56 MHz signal.

NFC readers will in the near future be used for point of 
sale card payments (contact-less cards) and will be 
installed at millions of merchant locations. They may turn 
into another source of noise on HF.

73, George