About
Welcome to my ham radio homepage! My name is Dilshan R Jayakody, and I'm a ham radio enthusiast based in the heart of Maharagama, Sri Lanka.
I obtained my initial ham radio license - a novice class issued by TRCSL - back in 2011 with the call sign 4S5DRJ. After upgrading to a general class license in 2014, I now hold the call sign 4S6DRJ. While my engagement with ham radio was on hold for several years due to career commitments, I'm excited to be back in the hobby as of 2023, continuing to build my shack and explore this fascinating world.
I am mainly active on digital modes, and I regularly upload my QSOs to LoTW, ClubLog, qrz.com, and qrzcq.com.
By profession I'm a software engineer, mainly working on embedded systems, operating systems, and video gaming. I'm also passionate about electronics - most of my electronic designs and builds are documented on my blog and Flickr pages. Beyond radio and electronics, I enjoy astronomy and Meccano (Erector) modelling.
Amateur Radio Projects & Articles
NOAA Weather Satellite Reception
Receiving NOAA weather satellite images on 137 MHz using a homebrew turnstile antenna, RTL-SDR, and PC. Antenna design based on work by Ivo Brugnera I6IBE.
SDR · Antenna
USB Morse Keyer
PIC16F886-based automatic Morse code keyer with USB and paddle interfaces. Works with a PC or a conventional Morse key.
CW · Microcontroller
Eddystone EC10 Restoration & PSU Add-in
Restoration of a vintage Eddystone EC10 MK1 communication receiver (10 PNP Germanium transistors, 550 kHz–30 MHz) plus an integrated 8V PSU.
Restoration
Trio JR-310 & TX-310 Restoration
Restoration logs for the vacuum tube / transistor Trio TX-310 transmitter and JR-310 receiver pair, manufactured circa 1960s by Trio Corporation (now Kenwood).
Restoration · Vintage
Homebrew 5-Element Yagi for 144 MHz
5-element Yagi-Uda antenna for 144 MHz built from common TV antenna parts. Achieved SWR of 1:1.1–1.2 on 145.625 MHz. CAD drawings available.
Antenna · VHF
100W RF Dummy Load
50Ω dummy load using two Vishay Sfernice 100Ω 50W thick-film resistors in parallel, housed in bonded-fin heatsink enclosures. Flat 1:1.2 SWR measured.
Test Equipment
455 kHz BFO for SSB Reception
Beat frequency oscillator module enabling SSB and CW reception on ordinary shortwave radios. Uses two NPN transistors and a 455 kHz ceramic resonator.
SSB · CW · Module
Modified Heathkit HD-1410 Electronic Keyer
Redesign of the classic HD-1410 keyer using modern, readily available transistors (KSP42, KSP10, KSP92) while retaining the original TTL chipset.
CW · Restoration
ICOM IC-R71A Receiver Restoration
Full recap and restoration of an ICOM IC-R71A quadruple superheterodyne HF receiver (100 kHz–30 MHz). Went from completely dead to outstanding performance.
Restoration · HF
13.8V – 5A Power Supply Unit
LM338-based 13.8V 5A regulated PSU for ham radio equipment, with MC3423 crowbar protection. A workhorse supply for portable transceivers.
Power Supply
Arduino superheterodyne receiver
Upgrade a traditional shortwave superheterodyne receiver with an Arduino base tuner.
Receiver · HF
Narrowband FM receiver for 2-meter band
MC3362 and ADF4351 based, modularized, narrowband FM receiver for 2m band.
Receiver · VHF
Resolving Keyboard Issues on the Sony ICF-SW7600GR
Outlines the diagnostic and restorative procedures I undertook to address a complete failure of the keypad on this radio.
Restoration · HF
4-Element Yagi antenna for the 2m band
Engineering design, construction, and performance evaluation of a 4-element Yagi antenna specifically optimized for the 2-meter amateur radio band.
Antenna · VHF
Surge arrester array
This is a simple surge arrester array I built in my free time, using BL-2000 lightning arresters.
Antenna · Protection
OpenHamClock Kiosk
This is an OpenHamClock kiosk using a Banana Pi M4 Zero SBC and a 10.1-inch LCD unit.
Software · Clock · Dashboard
ZZRX-40 Receiver build
Modified ZZRX-40 receiver build, using components that I could easily find in local shops.
Receiver · HFOther Radio, Transmitter & RF Projects
Projects related to radio and RF that are not directly part of the amateur radio section. Full details on my blog.
Web & Online
APRS Weather Station
LiveMy weather station transmits real-time meteorological data - temperature, humidity, wind speed & direction, rainfall, barometric pressure - into the global APRS-IS network under the callsign 4S6DRJ-13.
Live readings and historical graphs are available on aprs.fi. Data is updated continuously via the APRS internet gateway.
Ecowitt2APRS
SoftwareAn open-source Linux service I have been developing to seamlessly bridge Ecowitt-compatible professional weather stations with the global APRS-IS network.
The service receives data from an Ecowitt station and retransmits it in the standardised APRS weather packet format - making local weather observations visible to the worldwide amateur radio community.