speddmon Posted April 14, 2004 Report Share Posted April 14, 2004 Please help. I am curious about some of the components in this circuit. They are in particular L1 and L2. The circuit description says nothing about them but this, L1 and L1 Diameter: 5mm / Wire: 0.5mm / Spiral: 8. If anybody knows anything about this please inform me. Also, I would like to know which resistor I can swap with a pot to make it a variable gain amp rather than the fixed 20db?? Thanks in advance. Quote Link to comment Share on other sites More sharing options...
russlk Posted April 15, 2004 Report Share Posted April 15, 2004 L2 resonates with C5 and C4 near the center of the TV band. A 75 ohm resistor would probably work as well. L1 is a "peaking coil". It is self resonant near the upper edge of the band and is there to raise the high frequency gain. You cannot put a pot in this circuit because the leads have to be very short and this is a high frequency circuit. The ratio of C5, C4 could be changed, keeping the total constant, to change the gain. FYI: the total is (c5*c4)/(c4+c5). Quote Link to comment Share on other sites More sharing options...
BOHDA Posted June 23, 2004 Report Share Posted June 23, 2004 I take a look to your question.The L1 and L2 are made on an 5mm spiral drill,with an 0.5 mm wire,and have each 8 turns.There is nothing strange here,just usual indications for coils. Quote Link to comment Share on other sites More sharing options...
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