PhosphorFAX receives radiofax (HF weather fax) broadcasts in real time using your iPhone's microphone. Hold your phone near a shortwave receiver tuned to a coast-station weather fax and watch the surface analysis, wind and wave forecast or ice chart paint itself line by line, like paper coming off a recorder.
It sends as well. Turn a photo, a received chart or the built-in test card into radiofax audio through the speaker, or export it as a WAV.
No internet connection required. No external hardware. No account. Just your iPhone and a radio.
FEATURES
- Real-time radiofax receive via microphone — IOC 576 and 288, 60 to 240 LPM
- Automatic start and stop on the APT tones — arm it and walk away, it re-arms after every chart
- Phasing lock — straight charts from the first line
- Automatic slant correction from phasing, plus a slant trim for your phone's own clock
- Automatic centre tracking within 25 Hz of the tuned frequency
- Every chart stored with its demodulated signal — re-slant and shift the line start after the broadcast has gone
- LINE SCOPE and FAX HEALTH panels — level, tuning and phasing at a glance
- Live FFT spectrum and scrolling waterfall with black, centre and white markers
- Station list for 22 coast and met stations worldwide, with dial frequencies for USB
- Chart log with zoom, levels, rotation, invert, share and save to Photos
- SEND a photo, a chart or a test card as radiofax audio, or export it as a WAV
- Paper, phosphor or negative chart rendering
- Green and amber phosphor CRT themes with scanlines, vignette, and glow effects
- No accounts, no tracking, no network access
DSP ENGINE
A purpose-built radiofax demodulator, written for PhosphorFAX, with automatic start and stop detection, phasing lock, slant correction and centre tracking. The same engine encodes for SEND. All signal processing runs entirely on-device.
DECODER ACCURACY
PhosphorFAX has been tested against synthetic charts across every line rate and clock error, and against real over-the-air recordings of US Coast Guard weather fax broadcasts. Results, decoded charts and a test-card WAV you can play to the app are in the decoder test report.
WHERE TO FIND RADIOFAX
- Northwood, UK (GYA) — 2618.5, 4610, 8040, 11086.5 kHz
- Hamburg/Pinneberg, Germany (DDH3, DDK3, DDK6) — 3855, 7880, 13882.5 kHz
- Boston, USA (NMF) — 4235, 6340.5, 9110, 12750 kHz
- New Orleans, USA (NMG) — 4317.9, 8503.9, 12789.9, 17146.4 kHz
- Point Reyes, USA (NMC) — 4346, 8682, 12786, 17151.2, 22527 kHz
- Tokyo, Japan (JMH) — 3622.5, 7795, 13988.5 kHz
These are assigned frequencies. Tune your receiver 1.9 kHz lower in USB so the signal centres on 1900 Hz. A shortwave receiver, SDR, or WebSDR audio played through a speaker is all you need.
SENDING
PhosphorFAX produces audio and never keys a transmitter. Putting that audio on the air needs an appropriate transmitting licence. Sending into a second phone or exporting a WAV needs none.
SUPPORT
Need help? Have a question, bug report, or feature request?
- Ask a question — get help with using PhosphorFAX
- Report a bug — let us know if something isn't working
- Request a feature — suggest improvements or new functionality
You can also browse existing issues to see if your question has already been answered.