Discrete-transistor 40m receiver from EMRFD

Interest Groups Amateur Radio
#1

Continuing the discussion from Build a 80m receiver class:

Hello folks,

I finished building, and debugging, my first discrete-transistor 40 meter receiver from the schematic in EMRFD. I had a resistor out of place, which hosed the mixer up and made it into a 1st class AM radio – complete with revival-style bible thumpers. After fixing that, I heard the glorious first CW signal near 7.010 MHz.

I didn’t have a LM386 (gain 200) on hand, so a LM380 (gain 50) plus a LF412N (gain 4) preamp was employed for the audio gain chain. This makes it easy to up the gain after the mixer for better performance, as the LM380 is a bit noisy.

Pictures and audio, or it didn’t happen.

IMG_20181014_221722
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Some JT65A at 7.075 MHz – excuse the poor quality audio. It was recorded by holding my cell phone up to earbuds and then post-processing with ‘sox in.wav out.mp3 gain 26 band 3000 2000’.

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#2

Nice!!!

I like your breadboard. :wink:

Honestly, I’ve never seen a circuit built on a piece of copper like this. It’s pretty neat!

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#4

I especially like your floating LM380 !

#5

Kickass – will definitely sign up for your class…

#7

Think Walter used a similar build technique for his Michigan Mighty Mite classes.


Called it “Manhatten style”" build.
https://hackaday.com/tag/manhattan-style/
http://www.unixnut.net/files/manart.pdf

Walter and Bob Pease are smiling…

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#9

add -SA6 to prt no and add 6 GHz spectrum analyzer.
And then watch the clueless/careless blow the front end…

#11

I like the design.
Instead of making those “free floating” solder connections, you can take a piece of double-sided copper clad
pc board and cut narrow strips with a pair of tin snips and then cut those strips into squares or rectangles.

These small squares or rectangles can be soldered directly to the “main board” and then you can solder those
free floater connections to these electrically insulated pads. The free floaters can then be soldered from one pad to another which is electrically insulated and then solder the ends of those components that need to go
to ground to the main board.

Of course, you would be using the main board as a ground plane. This method makes for a little cleaner
“Ugly” board and easier to trace the circuitry.

Gary

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