radar MDF (= magnetic-direction-finding system)
Frank Kooiman developed the Lightning Radar that was used as single lightning station or in combination with a remote station. Lightning radar was an easy and very cheap (40 Euro) homemade system which consists of a power supply, an amplifier circuit, a double frame antenna and a free software. I used this system muntil 2009.
2. TOA (= time-of-arrival system)
Egon Wanke (Blitzortung.org) has designed an advanced lightning detection circuit. With the use of a GPS device we can determine the time of lightning stroke within 1 µsec. 4 stations have to detect same strike and with time-of-arrival calculations it is possible to determine lightning stroke position with an accuracy <1000m. This system uses same technology as ALDIS or BLIDS.
Costs are 140 Euro (preamplifier & evaluation board, GPS, box, power supply) with free software. See construction manual by Egon Wanke.
I also tried the Navilock EM-406A (with PPS output) with a SIRF3 chip for higher sensitivity (size of 30 x 30 x 10 mm). Now it is possible to receive the GPS signal inside a room (near the window).
Either you use the double frame antenna seen above under "lightning radar" or 2 small ferrite antennas by Wolfgang Friese mounted in the preamplifier board housing.