2B2C: Dual-band 2 channel QRP CW rig/ Part 4 Receiver build & test

Part 4: Receiver build & test.

Story and schematic:

'2B2C' is a project to design, build and document in a video series the design and construction of a two band (40 and 20m) crystal locked (channelised) QRP CW transceiver.
The rig is entirely scratch-built, from 'borrowed' designs, circuit elements and ideas. It is a compact, neat pocket rig that will provide more than adequate service as a simple parks and portable rig, but it comes into its own for SOTA where the crystal-locked channels will not be a major impediment to making contacts.

Frequency control is provided by separate dedicated and trimmed 7MHz and 14MHz crystal oscillators with buffers and with a fixed transmit offset.

The receiver is a conventional Direct Conversion design with strong band pass filtering and an SA612 mixer, followed by a dual op amp for audio filtering and gain, and an LM386 for headphone or speaker listening. It has ample gain both in the shack and on a windy summit.

The transmitter duplicates a significant part of the popular QCX and MTR radios using a high speed logic gate as a digital driver, to three BS170 FETs in parallel for a full 5 watts on both bands. Keying for a straight key is done using discrete components.

The receiver draws about 50mA and the transmitter up to 0.8A on key down. Band switching is done with two miniature telecom relays.

Part 1 - Concept
Part 2 - Receiver PCB
Part 3 - Receiver Band Pass Filters
Part 4 - Receiver build & test
Part 5 - Tx PCB, keying, pre-driver, LPFs
Part 6 - Transmitter driver
Part 7 - Transmitter PA and tests
Part 8 - Cabinet, panel, first outing

[davidtaylor]

Paul, good explanation of the trials in tribulations of getting homebrew analog circuitry working. Audio amps that howl, crystal oscillators that don't oscilate - all part of the fun! David VK3KR

[RAUK]

Every new video is like a little Christmas gift! Many thanks for doing it.

[yakovdavidovich]

Nice video, thanks! I'm enjoying the series. I'm about to order PCBs for my first full-suite transceiver build, so fingers crossed.

[docfoot]

Well done and i enjoy ur projects, I am the same i dont like throwing away components either hi hi 73's de ZL3

[indrajitR]

wow, why i did not much desired result with my project is lack of these test instruments.