30m Phasing Rx
I recently found an old project that had been left in the junk box unfinished. It's a direct-conversion phasing receiver for 30m.
Inspired by my current binge-listen to the Soldesmoke Podcast https://www.soldersmoke.com/ archives (I'm starting at the beginning and listening to them all.. currently I'm at around Episode 30) I thought I'd restart the project and build it into the planned-for 30m CW transceiver. There's a 5W PA strip that's recently been used in my QRSS MEPT but I'll build a new PA for the MEPT and use the original one for it's original purpose.
I repaired a few broken wires and dry joints and the RX is working. I've checked that the phasing opposite-sideband rejection is working and given it a tweak to check that the adjustments are doing the right things. All looks good.
I'll document the circuit later 
Here are some photos
There's a Makertube video of it receiving its first signals…
The design
Coming soon….
The basic format is
- Band pass filter for 30m
- RF amplifier
- Signal splitter to feed the RF ports of a pair of home-made passive 4-diode balance mixers
- the 2 mixers are also fed with 90° I & Q local oscillator signals from an arduino/Si5351 IQ VFO
- The outputs of the 2 mixers is a pair of baseband audio signals in quadrature which then pass through the phase-delay circuits
- The 2 paths combine such that the audio from the unwanted sideband is cancelled and audio from the wanted sideband is presented to to an op-amp audio BPF centred on 700Hz.
- Then there's a audio amplifier that can drive a speaker.
Further Information
Page created : 16/07/26 22:57 BST
Page updated : 16/07/26 23:28 BST