Sunday, December 4, 2011

Radio Direction Finder kit (DDF2020M)

DDF2020M Radio Direction Finder kit requires minimum assembly for 10~15 Minutes

The DDF2020M DF is an economical but very sophisticated Doppler DF “kit” with a GPS input, and RS232 output to provide the ability to indicate its location and draw bearing automatically or manually on Google Earth map to find the RF transmitter more conveniently.

DDF2020M kit Includes eight assembled / tested PC boards: MAIN board, 2 Sub boards, and 1 antenna board in the main unit. Completion work is required by the user to finish the DF main unit. Guidelines for the completion work are provided.

The user must provide a NB FM receiver, 5 antennas with mounts for external DF antenna unit and a PC for DF bearing (Windows OS). DDF2020 display program further requires a GPS receiver with NMEA 4800 baud output.

VHF Doppler DF – 5 Antennas primarily for mobile DF, 100~1000 MHz
Economy, high performance DSP / micro processor design, software intensive
Sold as a kit – Main unit, antenna unit and associated cables
RS232 output for Windows PCs (Agrello format)
Uses modified Joe Moell Wideband Antenna design
9 ~ 28 VDC operation
Optional GPS Receiver available.


Rcvr Freq: Determined by user-provided FM receiver, range 100 to 1000 MHz
Antenna: Four elements for DF and one auxiliary element for improving sensitivity and accuracy, wave vertical with assembled
Ant Scan: Scan rate 430 Hz, rotation clockwise (viewed from above antenna)
Ant Switch: Modified Joe Moell Wideband Doppler DF antenna design
Employs Agilent HSMP3893 SMT PIN diodes
SMT / stripline circuit design, SMA output connector
Audio Input: FM receiver speaker audio, 1.0K ohm load. 25db dynamic range.
GPS Input: 4800 baud RS232 input, NMEA $GPRMC, $GPGGA and / or $GPVTG messages.
Output 1: RS232 Agrello DF message, 4800 baud, 8N2. (15 messages / second )
Ant Outputs : Four discrete active HIGH outputs for DDF 2020 Antenna ( one per antenna )
DC Power : 9 ~ 28 VDC
Voice Filter : Switched-capacitor filter, (SCF) 4 sections. Bandwidth 0.2 Hz
Multi Display

The MultiDisplay of DDF2020M provides a combined numeric and pelorus display in the main board. A high quality display, with 2 microcomputers and an RS232 input that accepts Agrello DF messages.

The pelorus display employs 36 high density LEDs, with 4 yellow LEDs at cardinal headings. Option straps allow “hold/blink” of last valid DF data, or pelorus “orbit” when data goes invalid. All LEDs briefly “flash” (2 second intervals) for enhanced nighttime viewing

3 digit numeric readout, 0.36 inch characters
36 LED pelorus display, 4 yellow cardinal LEDS
Selectable HOLD/ORBIT display for old DF data
Power-on self-test


My Stamp Collecting Blog

Counter Added January 1, 2011

free counters


The A index [ LOW is GOOD ]

  • 1 to 6 is BEST
  • 7 to 9 is OK
  • 11 or more is BAD

Represents the overall geomagnetic condition of the ionosphere ("Ap" if averaged from the Kp-Index) (an average of the eight 3-hour K-Indices) ('A' referring to amplitude) over a given 24 hour period, ranging (linearly) typically from 1-100 but theoretically up to 400.

A lower A-Index generally suggests better propagation on the 10, 12, 15, 17, & 20 Meter Bands; a low & steady Ap-Index generally suggest good propagation on the 30, 40, 60, 80, & 160 Meter Bands.

SFI index [ HIGH is GOOD ]

  • 70 NOT GOOD
  • 80 GOOD
  • 90 BETTER
  • 100+ BEST

The measure of total radio emissions from the sun at 10.7cm (2800 MHz), on a scale of 60 (no sunspots) to 300, generally corresponding to the sunspot level, but being too low in energy to cause ionization, not related to the ionization level of the Ionosphere.

Higher Solar Flux generally suggests better propagation on the 10, 12, 15, 17, & 20 Meter Bands; Solar Flux rarely affects the 30, 40, 60, 80, & 160 Meter Bands.

K index [ LOW is GOOD ]

  • 0 or 1 is BEST
  • 2 is OK
  • 3 or more is BAD
  • 5 is VERY VERY BAD

The overall geomagnetic condition of the ionosphere ("Kp" if averaged over the planet) over the past 3 hours, measured by 13 magnetometers between 46 & 63 degrees of latitude, and ranging quasi-logarithmically from 0-9. Designed to detect solar particle radiation by its magnetic effect. A higher K-index generally means worse HF conditions.

A lower K-Index generally suggests better propagation on the 10, 12, 15, 17, & 20 Meter Bands; a low & steady Kp-Index generally suggest good propagation on the 30, 40, 60, 80, & 160 Meter Bands.

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