Overview
The PicoDopp is an economical, high-precision pseudo-Doppler radio direction finder (RDF) kit designed for mobile and fixed-station signal localization. Engineered by Bob Simmons (WB6EYV) under the Doppler DF Instruments brand, the hardware functions by electronically cycling an external multi-element antenna array to induce a phase-modulated tracking tone onto an incoming radio signal. The platform interfaces with localized terminal mapping utilities and global positioning sensors to automate mobile transmitter hunting, rescue telemetry tracking, and competitive radio foxhunting operations.
Technical Specifications
| Attribute | Details |
| Manufacturer | Doppler DF Instruments |
| Product Category | Pseudo-Doppler Radio Direction Finder (RDF) |
| Core Operating Method | Solid-State Antenna Commutation with Switched-Capacitor Filtering |
| Commutation Switching Frequency | 430 Hz Audio Modulation Pattern |
| Supported Antenna Matrix Layout | 4-Element or 8-Element Symmetrical Square / Circular Arrays |
| Native Data Output Format | RS-232 Serial COM Port (Standard Agrello DF Text Strings) |
| Supplementary Wireless Port | Integrated Infrared (IrDA) Telemetry Transmitter Output |
| Input Data Parsing Protocol | NMEA-0183 Serial GPS ($GPRMC, $GPGGA, $GPVTG Sentences) |
| System Operating Voltage | 7 Volts to 12 Volts DC nominal |
| Typical Current Consumption | 30 milliamperes (Main Board assembly load) |
Physical Description
The baseline PicoDopp package is produced as an original equipment manufacturer (OEM) kit comprised of six pre-assembled and tested printed circuit boards. This internal configuration features one centralized Main processor board, one primary Antenna commutation distribution board, and four standalone RF Termination boards designed to mount directly to the bases of user-supplied vertical antenna whips. The modular processing layout is engineered to fit inside low-profile shielded project enclosures, leaving the front panel layout adaptable for custom alphanumeric LED rings, pelorus bearing arrays, or standalone serial-to-digital interface connections.
History
The PicoDopp was introduced by Bob Simmons to bridge the market gap between rudimentary homebrew directional antennas and complex commercial signal intelligence hardware. Early radio direction finding tools required operators to physically rotate high-gain directional beams while driving, a technique that was highly prone to multi-path errors in dense urban or mountainous areas.
Simmons bypassed these mechanical constraints by deploying a solid-state PIN diode matrix on the input antenna rail. The processor switches power across four or eight identical stationary whips at a sequence rate of 430 pseudo-revolutions per second, tricking a standard narrowband FM receiver into recovering the phase variations as an acoustic audio tone.
The underlying firmware was continuously optimized to enhance multi-path resistance by using narrow band-pass filtering and intelligent averaging routines to isolate the target signal from background vocal or data modulations. Simmons incorporated bidirectional data connectivity into the mainboard chip, allowing the system to ingest standard NMEA global positioning data strings directly.
The controller combines the vehicle’s dynamic GPS vector coordinates with the raw radio bearing phase angles, calculating a true north-stabilized azimuth direction. The design served as an industry open-source development standard and was subsequently licensed for commercial assembly enclosure models, including the Global TSCM Group DDF2020T dashboard tracking platforms.
References
- https://home.hiwaay.net/~pelican2/ – Product index outlining pricing matrices, hardware component lists, and software package compatibility for the PicoDopp kit.
- https://home.hiwaay.net/~pelican2/PicoDopp/COMPLETION.html – Technical installation blueprint defining antenna array spacings, receiver detector rules, and serial NMEA GPS sentence parsing protocols.
- http://www.homingin.com/tscmfix.html – Technical evaluation log assessing the performance, commutation switching parameters, and commercial variants of the core PicoDopp processor tracking architecture.