ADX-S Superhet QRP Transceiver Kit by CRKits
Improved ADX variant by Adam BD6CR featuring a superheterodyne receiver with 455 kHz IF and ceramic filter for reduced broadcast interference, available as a 4-band or 7-band kit supporting FT8, FT4, JS8Call, and WSPR.
Overview
The ADX-S (ADX Superhet) is a modified version of the original ADX digital transceiver, designed by Adam Rong (BD6CR) of CRKits. The key improvement is replacing the original direct conversion receiver with a superheterodyne architecture using a 455 kHz intermediate frequency and ceramic filter, which significantly reduces broadcast interference (BCI) — a common complaint with the original ADX design.
Key Improvements Over Original ADX
- Superhet receiver with 455 kHz IF and ceramic filter for better selectivity
- Reduced broadcast interference compared to direct conversion design
- 3.5W output on 20m and lower bands
- Board size: 97mm x 97mm (three PCBs sandwiched together)
- All through-hole components — no SMD soldering required (Arduino Nano and Si5351 modules come pre-assembled)
Available Configurations
- 4-band kit: 40m, 20m, 15m, 10m
- 7-band kit: 40m, 30m, 20m, 17m, 15m, 12m, 10m
Supported Digital Modes
- FT8, FT4, JS8Call, and WSPR via WSJT-X software
- Also works with FT8CN Android app as an alternative to a PC
Community Reception
About 30 local hams tested prototypes and provided feedback before the kit's commercial release. The ADX-S has been reviewed by VK3YE (well-known QRP YouTuber) and featured on QRPer.com. Multiple amateur radio bloggers have documented successful builds and made contacts over 5,000 miles on 20m FT8.
Build Difficulty
Medium — the closely-spaced solder pads require care, but all components are leaded (through-hole), making it accessible to builders with basic soldering experience. The kit is available from CRKits.com for approximately $69 USD.
