Krystalka s fetem
Autor: Krysatec <krysatec(at)post.cz>,
Téma: Schémata, Vydáno dne: 05. 12. 2007
Ramonovy zkušenosti ze stavby (v anglickém originále!)
Novy2
Hello,
I tested the MOSFET ALD110900A with a frame (loop) antenna wound on a 22cm x 22cm cross- section cardboard (carton) box. I used 20 turns of plastic insulated stranded copper wire AWG 22. A polyvaricon (plastic insulated 365pF variable capacitor) was used for tuning in stations. Couldn´t couple conveniently the frame antenna to the ALD.The coupling turn (or turns) would load down the frame tuning circuit.
On the other hand, the frame antenna wound on a cardboard box proved being a great performer for a simple crystal radio using a conventional germanium diode. The only concerns worth taking into account are that the diode should be a carefully selected one for sensitivity, the use of an audio matching transformer is a "must", magnetic earphone elements from old telephones of the 80's yield better sensitivity than the common piezoelectric ceramic earphones, even when impedance matched.
I am now working on a 44cm x 30.5cm cross-section loop antena, also wound on a cardboard box.
Last night I tuned 8 stations 10~15km from my home, 10kW to 35kW with a 22cm x 30.5cm frame antenna (23 turns gave 340uH for a 260pF variable capacitor). Looks promising playing with these frame (loop) antennas for MW listening. It is a pity that NDB (non-directional beacons) LW stations were shut down in my country. Listening to them with a 2m x 2m loop would have been a nice experience. Am I correct?
Very best regards,
Ramon