Author Topic: 5W PLL  (Read 3105 times)

MDH

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5W PLL
« on: August 27, 2012, 04:00:16 pm »
Hi everyone. I've been following the pira site for a good few years so i thought i'd join the forum.

I'd like to know more about the 5w pll tx http://pira.cz/entx4.htm

I want to know more about TR1. Is this part of the matching between stages? is there an alternative? for example using a toroidal ferrite or even just a capacitor? also, what is R9 for on the base of Q3?

The oscillator looks like it operates 'on frequency', am i right?




DJ Adam Eve

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Re: 5W PLL
« Reply #1 on: October 03, 2012, 09:33:45 am »
Hi everyone. I've been following the pira site for a good few years so i thought i'd join the forum.

I'd like to know more about the 5w pll tx http://pira.cz/entx4.htm

I want to know more about TR1. Is this part of the matching between stages? is there an alternative? for example using a toroidal ferrite or even just a capacitor? also, what is R9 for on the base of Q3?

The oscillator looks like it operates 'on frequency', am i right?





TR1 is an impedance transformer, stepping down the impedance from the BFG135 to the base of the 2n3553/2sc1971, hence they have different windings for each. From memory i think the ratio is 3:1 or 2:1, that's the turns ratio, which is the square root of the impedance ratio (so impedance ratio is either 4:1 or 9:1), so for the 2:1 ratio you could use a bifilar 4:1 torroidal transformer (Google) but why bother? There's alternative ways to build it with ferrite beads.

The oscillator is 'at frequency' and puts out a fair bit of power.
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