Students returned here again. This time they had prepared a lot more for display. They have now decided, as I suggested, to reduce the size of the gadget that everyone would carry with them.
As per the original design, the signal generator gadget sends digital codes as an identification for an individual sender. The transmission is at a given higher frequency, using FM. This would mean that all receiving stations (which are used in triangulation) operate at one frequency, and a person's id is the digital signal sent at that frequency.
Now, we will use individual frequency transmission as an id. we may have to do further tricks, since this might mean very narrow bands and FM using highly accurate filters, etc. one could explore if we could do a crude digital signaling. One could just change the ON/OFF frequency of individual receivers, providing another way of identification...
This circuitry could work close to 65 MHz, providing most of the amplifiers and filters that we need for our radio telescope ;-)