Allegro Razor Blade Sharpener

I used a Jack plug and fitted a Germanium diode and capacitor and a resistor and was able to make tuned receivers for many stations, plugged into the record player they worked fine and I used an LCR bridge to tune them.. wire about 12 " long for local stations but weaker stations a wire across the flat roof. They worked much better at night.

Clive

Red spot transistor 7/6d and white spot (for rf) 15s if I remember right. Used to use reflex circuits so that the transistor first amplified the rf and the detected signal was fed back round so that the same transistor amplified the audio.

Russell

Now that MW is all but dead, can you make a simple crystal set to pick up FM ?

BobH

Hi BobH,
Theoretically it should be possible but you would need a very high Q tuned circuit so that the 150 Khz (which is only a small percentage change in the frequency of about 90 Mhz. ) deviation of a broadcast FM signal moving up and down the slope on one side of the tuned circuit frequency response transformed it into a varying amplitude. You would also receive the signal at two tuning positions. One either side of the frequency response curve of the tuned circuit.

Les.

In my days of crystal sets a good long arial and good earth was essential, all the power supply came from the radio signal. The only essential, had to be paid for, was a high-resistance earphone. Plenty about ex government. Tuning coil on varnished cardboard tube with a slider for tuning, razor blade or real diode and you were away. I am sure signals were more powerful in those days, only long wave and medium to worry about, on long wave you good get broadcasts from all over the world in good conditions.

ok. on the subject of on unauthodox semi conductors..

zinc oxide diode

flame diode

magnetic amplifiers

Edited By jason udall on 29/03/2015 13:52:45