ADX-S Digital Modes (WSPR, JS8, FT4 and FT8) HF QRP Transceiver Kit with 40, 20, 15 and 10 meter LPF Band Modules

Unit Price: 69 USD including tracked air shipping.

New! ADX-S V2 Kit covering 40, 30, 20, 17, 15, 12 and 10m band with Automatic band module detection, TCXO module, Bluetooth module and Audio Cable Adapter Kit

Unit Price: 89 USD including tracked air shipping.

Photo: BG7IKK who built the ADX-S kit and achieved over 18,000 km DX with his EFHW antenna. Click the photo to enlarge.


The ADX-S Digital Modes HF QRP Transceiver is the Superhet modification of Barb, WB2CBA's open source Arduino Digital Xcvr inspired by the receiver design idea of JA9TTT. The receiver performance is much improved compared with the original direct conversion design at the cost of adding only two components. Several hardware and firmware bugs are fixed so you can build with better experience, thanks to the feedback from dozens of the beta testers and early domestic customers. The code is open source so you can customize the radio with your own idea. It works with WSJT-x, JTDX on PC or FT8CN on Android phones in VOX mode.

New! iFTx on iPhone or iPad is also supported on V2 hardware with Bluetooth audio connection.

ADX-S Review by Peter Parker, VK3YE

ADX-S V2 Field Demo by BD6CR in English


ADX-S eHam product review

Paper based:

  • CQ-DL in Germany on the latest Feb 2024 issue.
  • QEX Japan on the latest March 2024 issue.
  • Swiat Radio in Poland on the May/June 2024 issue.

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Generic TCXO Module for Adafruit Si5351A Clock Generator Breakout Board and its Compatible (Green one on the left of the photo, not including the entire module on the right)

Unit Price: 9.9 USD for 1 pcs, 19.9 USD for 3 pcs or 29.9 USD for 5 pcs including tracked air shipping.



Why you will need this TCXO Module? No more noticeable drift on ADX-S, even WSPR at full RF output! Now it is a part of ADX-S V2 kit. The TCXO spec says 0.5ppm drift and 2ppm accuracy.

Rework instructions:

  1. Desolder the original SMD crystal. Hot air or heating plate are the best. If you don’t have either of them, a solder iron of high power (60-100W) will do the job. Just touch the metal surface and wait for solder melt and then move the crystal towards empty PCB side. Clean the pad if necessary.
  2. Apply solder to three empty pads XA, V and G, use solder bridge to solder on V and G pads to the decoupling capacitor on the Si5351 module, then use a thin lead to connect the XA pad to the top right pad of the original crystal.
  3. You may need to re-calibrate the crystal as the crystal frequency changes. No other change is required. It is a drop-in upgrade for other applications than our ADX-S.


Classic PCB Kit (CPK) Series

Tracked air shipping is included in the price. Please note, DC40 kit does not include NE602, which I hope you can supply by yourself.

If you wish to get the CPK3 SMD part pre-assembled, please refer to this post.

CPK1 = Pixie2023, CPK2 = DC40, CPK3 = KT Receiver


CPK-1 Pixie2023: CW Transceiver with clean output

CPK-2 DC40: Clear receiver with less broadcast interference

CPK-3 KT: Modern FM/MW/SW receiver for minimalists


You can share the kit building fun with club members and youngsters with these classic PCB kits. For example, after the SMD part pre-assembly, some primary school students of BH4GYJ (Shanghai Fushan Foreign Language Primary School Club Station) can build CPK3 KT Receiver successfully with the help from their teacher Mr. Li, BH4FGJ. Read this post.

Pixie2023 Review by Peter Parker, VK3YE

DC40 Short Test Video by JL1KRA

CPK-3 KT Receiver Review by Peter Parker, VK3YE

CPK-3 KT Receiver in Case and More Listening by VK3YE

CPK-3 KT Receiver Kit Listening from Beach by VK3YE

WB2CBA Barb's Review of CPK-3 KT Receiver

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13 Transistor Transceiver for Digital - 7074 USB

Unit Price: 59 USD including tracked air shipping. All the parts and case are included.


Can you build a 1-watt FT8 SSB transceiver by only 13x 2N4401 transistors? This thread contains all the information about this traditional kit of all through-hole parts.

Dimensions: 103mm depth x 88mm wide x 38mm height
Weight: about 235 grams w/o internal batteries
Frequency and Mode: 7074kHz USB
Filter: 4x 7078kHz crystals covering around 7075.5-7077kHz
Audio Pass Band: around 1500~3000Hz
PTT Control: VOX
Receive Current: around 50mA
Transmit Current: around 300~350mA
Transmit RF Power: around 1-Watt
Spurious suppression: -53dBc

Kit Assembly Manual Rev. B, FT8CN Operation Added

Schematic: Inspired by VK3YE Knobless Wonder and K1SWL Warbler with improvements

New Review by Peter Parker, VK3YE

eHam product review average rating 5.0/5.0

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R3500D ARDF Receiver Kit

Unit Price: 39 USD including tracked air shipping. Earbuds are removed from the kit as they are magnets.


R3500D is the upgraded version of the well known PJ-80 80m direction finding direct conversion receiver kit. 3500~3600 kHz coverage. Case color is random in black, orange, green and blue.

A well written kit assembly manual by Jack Purdum, W8TEE Al Peter, AC8GY for Youth On The Air YOTA Region 2 Camp June 21-26, 2020

Video review by Peter Parker, VK3YE

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Note that the LO frequency is at half of the working frequency. It is by design, no worries.

Step by step building video

PJ-80 eHam product review average rating 5.0/5.0


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