FreeDV Ham Radio digital voice software

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FreeDV is an application for Windows and Linux that allows any HF SSB radio to be used for digital voice mode with a bandwidth of just 1.1 kHz

Speech is compressed down to 1400 bit/s then modulated onto a 1100 Hz wide QPSK signal which is sent to the Mic input of a SSB radio.

On receive, the signal is received by the SSB radio, then demodulated and decoded by FreeDV.

Features

  • Codec 2 voice coder and FDMDV modem
  • 50 baud 14 QPSK voice data
  • 1 Centre BPSK carrier with 2x power for fast and robust synchronisation.
  • 1.125 kHz spectrum bandwidth (half SSB) with 75 Hz carrier spacing
  • 1400 bit/s data rate with 1375 bit/s open source Codec 2 voice coding and 25 bit/s text for call sign ID
  • No interleaving in time or FEC philosophy resulting in low latency, fast synchronization and quick recovery from fades.
  • 44.1 or 48kHz sample rate sound card compatible

Watch FreeDV, the new HF digital audio program for Radio Amateurs.

RF Spreadsheet now online

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Andy Foad (G0FTD) has made a collection of RF calculations available in an online Google spreadsheet.

Amongst the calculations are:

  • RF Loss though concrete
  • Barometric pressure conversions
  • Maidenhead distance and beam heading calculator
  • Audio filters (RC networks)
  • Unknown feeder impedance calculator
  • Loop antenna impedance calculator
  • FM bandwidth (Carson's rule) now includes modulation index.
  • L network matching component values<
  • Capacitive and inductive reactances
  • Bandwidth tuned circuit
  • Radio range and VHF/UHF/Microwave
  • Freespace path loss
  • Resonance series tuned circuit
  • Resonance // tuned circuit
  • Power received from tx to rx
  • Groundwave range calculation
  • Near field (REACTIVE) region of an antenna
  • Calculation of skin effect on conductors (2 methods)
  • Series Resistance calculator for LED's, Lamps and crude nicad charging
  • Impedance calculator including phase and power factor and relative SWR.
  • Quarter wave transformer calculator
  • Electrical quarter wave calculator
  • Impedance of custom air spaced coax
  • Air spaced capacitor designer
  • All of Ohms law and power laws
  • Conversion of AC and DC values RMS etc
  • Conversion of milliwatts to dbm
  • Conversion of dbuV to dbm
  • Amidon cores inductance designer and related info included.
  • Power and voltage decibel ratio's.
  • Coax losses and approx capacity per 30cm
  • Coax voltage breakdown and capacity per foot
  • Single layer air cored inductance designer
  • Capacitor markings guide
  • SPARK GAP DISTANCES
  • Resonant speaker tubes to act as CW peak filters
  • db versus multiplication factor both power and voltage
  • Galactic noise levels
  • uV to dbm converter
  • Milliwatts to dbm converter

You can download the spreadsheets from https://sites.google.com/site/g0ftdradio/home/rf-spreadsheets

RSARS e-docs library available online

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The Royal Signals Amateur Radio Society (RSARS) has made available a number of articles in PDF format.

In their e-docs library is an extensive collection of articles on HF Antennas and Projects.

RSARS e-docs library - http://www.rsars.org.uk/ELIBRARY/edocs.htm