My BTTF 2006 Crystal receiver.
The measured LC circuit is the antenna tuning circuit, this one is identical to the detector circuit (same L and C). Here I came to a bandwidth of 6.9Khz at a frequency of 1.6Mhz. Lowest frequency at the -3dB point is 1.598Mhz, Upper -3dB point is 1.6017Mhz.
The resistance RL has to be three times Rp, the headset/speaker has to be matched to the this value, the diode Rd also needs a value of RL, I took the average of 519KΩ and 402KΩ , 460KΩ x 3 = 1380KΩ. So I came to the conclusion to use the HSMS286K diode with a Rd of 1476KΩ, according to Dick Kleyer`s diode table.
The last measurement at 531khz also gives an improvement in the Q-factor of my coil , this is due to the setup I used to measure and my FET amplifier. Here the Q went up from 175 to 483,..this because the circuit has lesser loading.
The Q also will go up more if I clean up my desk more,...but hey,...all the crap is also lying there when I use the crystal receiver,...so why bother to get a higher Q just for statistics.
Long wave crystal.
While at it I quickly build a
"Long wave" crystal receiver. I used a 1000pF var.Capacitor and a coil of 900ÁH.
This one is wound on a 5cm diameter cilinder using 0,5mm thick enameled wire. On
one side of the LC circuit is connected the antenna and on the other side earth.
Crystal (diode) used is a schottky diode. Audio transformer connected,
headphone,...results... about 6 stations at 16.30 in the afternoon.
The "Woods metal" or "Cerrobend" I got from the UK: