Tuesday, November 12, 2013

Diode Product Detector

Diode product detector. 4 diodes used are matched 1N4148. How to match ? using the dc resistance in DMM (digital multimeter). Try a dozen resistor. Measure and write down their resistance. Now choose 4 with closest resistance.

Balun core or any RF toroid can be used.

SWG 30 wire 3 strands twisted.

Both transformers are identical. Resistor is used to take the AF and audio is given to AF Filter..
product detector
Product detector. This is standard circuit. I was making the receiver and for the sack of go or nogo test connected the diode dbm and presto it worked first time. It lacked the audio so i put the resistor as shown and it became my favourite. It is given in the QRP Notebook also.

tifiliar transformer
How to wind the core ? Make a trifiliar wire. Three wire is taken and twisted for 5 to 8 turns per inch by handdrill. then wound the 15 to 17 turns. One side wire end are labelled as 1,2,3 and their other ends are labelled as a, b,c. Test for dc continuity. 1-a,2-b,3-c and no other pair should show the zero. If it shows then wire enamel is broken and it needs to be rewound using new wire. Connect 2and a and your transformer is wound ok. Becareful with scrapping the enamel.