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Practical Wireless Direct Conversion Receiver : January 1978

I'm not a great fan of the LM380, but I didn't let that stop me from building this receiver from Practical Wirelessback in 1987/1988.

PW DC receiver schematic

My DC receiver schematic

Somewhere along the way I stripped it for spares (well, the MOSFET transistor, mainly) so when I recently found it again I figured I'd revive it.

I originally used toroids (I had a bit of an obsession with toroids in the eighties) and at some stage I also tried a Denco coil, hence the socket.

Winding a coil

A long time ago I actually bought some clear nail varnish -- these days I just use what the womenfolk throw out.

Input stage with new coil

The transistor is supposedly a BF964. It's from eBay, and they work, but they're unmarked so who knows.

Applied power, and couldn't get the VFO to oscillate. The voltage over the zener was about a volt low, so I changed the zener, and while I was there I changed the 2N3819 as a precaution, but it turned out the diode on the gate was shorted. Replaced that as well.

OnSemi datasheet extract Fairchild datasheet extract

This brings us to something interesting. Fairchild says the pinout is Drain Gate Source. ON Semiconductor differs, specifying Source Gate Drain. Vishay agrees with ON Semi, and this also matches the PCB overlay, so that's what I used, but maybe it doesn't matter...

Bottom line: I like my PW Sudden better.

[Image] Hit Count hits since 2015-02-27.

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