Encrypted HF Chat: First Field Test

First field test of encrypted chat over HF radio. Georgia to Michigan, VARA HF in 2300 Hz wideband mode, Reticulum handling Curve25519 key exchange and AES-256-GCM encryption with forward secrecy. The link held for 24 minutes through SNR as low as -17.1 dB. Zero errors. Clean disconnect.

The signal degraded throughout the session. Early readings averaged +3.3 dB. The final third averaged -7.0 dB. VARA spent 56% of the session at its minimum speed level: 18 bps, roughly five characters per minute. The link never dropped.

The overhead problem:

Only 23% of transmitted bytes were actual chat text. The rest was security packaging. Type “test” (4 characters) and the system sends 102 bytes over the air. The fixed per-message cost breaks down like this:

At 18 bps, those 110 bytes cost 49 seconds of airtime before a single character of text goes out. A max-length 408-character message is 10x more efficient than a 4-character message. Every message pays the same tax.

Why 500 Hz mode changes everything:

The 2300 Hz mode spreads power across 52 carriers. At -3 dB SNR average, each carrier got almost nothing. 500 Hz mode concentrates the same power into 2 carriers. Under these conditions, 500 Hz would have sustained 88-177 bps (SL4-SL5) instead of 18 bps (SL1). Same radio, same power, same path.