Crystal receiver for the  BTTF 2006

Hi all, here some updates,

For the 2006 BTTF contest I spent some time modifying the last years receiver, that one seemed to be good, I won the contest, but everything can be improved, how good it is. I enjoyed working on these receivers, it just happens to get first place.

Only thing what is the same with last years receiver, are the spiderweb coils, made out of 440/46 Litze on a polypropylene form. The variable C`s are from an old salvaged tube receiver and are approx. 500pF. I cleaned these ultrasonic. And are operated through a General Electric vernier drive with 1:50 reduction.

The C`s and reductions are coupled with eachother through ceramic insulators, and bolted onto a flat piece ofpolypropylene.

The detector diode is not a 1N34 like last year, but a HSMS2865 schottkey diode (2 diodes in 1 smd housing) . On the receivers output not a 1925 bakelite headset. Now there are 4 transformers. The primairy sides of these are coupled in series to get 80KΩ x 4 = 320KΩ. Secundairy sides are 2x2 in series and then in parallel to get 8Ω again. Then a Bogen T725 is connected to that 8Ω. The secundary side of the Bogen is connected to a "soundpowered decktalker" with a impedance of 130Ω.

I measured the LC circuits on their bandwide with my DDS generator and scope. Band wide is about 3Khz (-3dB point) wich is a Q of approx 175 at 531 Khz.

Here the complete loglist