BTTF listening contest, 2005
I already had some experiance building honeycomb and other coils for crystal radio`s,..so it was time to make a contest receiver. I used a diode (1N34) instead of a real crystal .
And there is also a description of the picture above,..from left to right:
Left you see the antenna tuner capacitor,..unknown origin but 2x500pF in series,...so 250pF.
Next the first LC antenna circuit, a spiderweb coil with 45 windings made out of 440/46 Litze on a polypropylene coilform and measures 215ÁH. Parallel on the coil a Hammerlund variable C of 300pF, operated through a 1:5 reduction with a ceramic insulator in between to reduce hand capacity.
I measured the circuit on its bandwide and Q
factor. Bandwide is aprox 4.7Khz, a Q of around 212.
Next you see the detecor circuit, made from a identical coil with a value of 215ÁH. Tuning capacitorparallel on the coil and is also from an old tube radio and the value of that one is 500pF.
I also measured this circuit at 1Mhz (1000Khz) and the bandwide is here 6.4Khz. The impedance of the circuit is: Z = 2 x pi x f x L x Q, Z = 2 x pi x 1000000 Hz x 0,000215 H x 156. Z = 210.631KΩ
The LC on the right is the wavetrap made out of 45x0,007mm litzewire and measures 230ÁH, the capacitor is a Hammerlund and measures 230pF. Q of this circuit is around 95. Its low because of the used litze wire,..the more little wires,..the better the Q.
Headset is a real old one, from around 1920/25. It
has a resistance of 3KΩ with a impedance of around 15KΩ. This is ways to
low in combination with the impedance of the detector circuit. But it
has to do the job when you don`t have anything else.
of what I heard with this set during the contest.
Couple of months later...
Saturday morning, 1th of April, 2006 (no kidding)
I think I`ll go teo the BTTF homebrew day at the town of "Kootwijkerbroek", lots of noce things to see there I hope,..and I send in a log of the last BTTF contest, so let`s see where I ended.
Coming inside I just missed the opening speech, so I wnt to the bar to get a nice hot cup of coffee, as I came on my motorcycle and it was cold outside. Well, they announced that the homebrew/contest prizegiving started so I went to that hall and took a seat.
Homebrewers with there radios were around 5 or 6,..not many.
Listeners there were 7,..so I got the 7th place was my opinion,..as Dick
Kleijer also participated and he is gooood. Well I had no 7th
place,..5th place,...Dick Kleijer,...hmm,..not his style I
thought,...did I log more stations as he did?? Third place,...Lisa
Leenders. What the....? Did the lost my log or did the forget
about my log. In the end I took first place,...me?..first time in a
contest with a crystal radio.
Hopefully next year there will participate more people, so get a
more contest like feel.