Building a Direct Conversion Receiver: Part 4

QSX Update: January 2019

KI7MNW’s Homebrew QRP Transceiver

Cameron Tribe, KI7MNW recently posted his homebrew QRP transceiver on the Amateur QRP Radio group on Facebook. It’s completely scratch built and borrows design elements from several sources including the BITX40. Follow all the way to the bottom for a picture gallery, schematics, and source articles.

Tonight I finished my homebrew 40m QRP transceiver. I’ve put a lot of hours into this rig and it feels good to have it all put together. I’ve learned a lot from this build from both experimenting with new circuits and breaking lots of parts. 
The receiver design is based on KK7Bs Classic 40, and the transmitter is based on the Bitx40. It runs off four internal series RCR123A cells with the option to switch to higher capacity external battery pack. There is undervoltage lockout protection that keeps the cells above 3V per cell.


Transmit: 37dBm
Second Harmonic: -57dBc
Minimum discernable signal: -120dBm
RX Draw: 28mA
TX Draw:800mA
Status LED for RX, TX, & low voltage

The Reverse Beacon Network confirms that test transmissions made it from BC to Texas from my QTH in South Central Washington.

I built this with the intention to take this with me in my backpack on hiking and camping trips this coming Summer. Now I need to put together a random wire and a 9:1 unun to bring along with me!

Video and Gallery

Downloadable Reference Articles

Thanks to Cameron for sharing. Surely it’ll be a great QRP rig for your hikes in the beautiful PNW!

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