Sunday, 3 May 2020

Shortwave Receiver

VFO











BPF, RF Amplifier, IF Amplifier, AM Envelope Detector







Final detector was a infinite impedance.


Note: there is another 10nF cap across the 47uF decoupling cap (not shown).




6 comments:

  1. Beautiful VFO Charlie. I especially like the variable cap and freq readout counter. What are you using for the main coil? Have you checked stability yet? (After the hot solder cools...) 73 Bill N2CQR

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  2. Hi Bill. The coil is an air core out of an old FT101. The form is made of ceramic which should be nice and thermally stable. As for stability, I'm really pleased with it. Once it's warmed up is still to be very good. I have not, however, gone out of my to offset pos and neg temp coeff components. Hand capacitance is not an issue too, which is great.

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  3. I have one of those old FT101 VFO assemblies. I removed the knob that came with it for another project, but still have the rest. The vfo has a diff trimm cap, and two fixed caps with neg and pos temp coefficient which could be used to set for zero drift over time.

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    Replies
    1. I still have those. At the moment it is not too bad at all. Not perfect, but certainly usable.

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  4. Interesting. Thank you for sharing your progress. It is such an inspiration.

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    Replies
    1. Thanks. I have changed the detector to an infinite impedance one. I'll post that soon.

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