HzDrop

Ready

Send

0 bytes · —

Receive

Received text appears here

Text or file

Signal & packet details

Spectrum

Audio inactive
02 kHz4 kHz6 kHz8 kHz

Microphone input while listening; generated signal while sending. The chart runs only while this panel is open.

Sending Ready

Choose a profile and enter a message.

Receiving Not listening

Waiting for a valid packet header. All profiles are detected automatically.

No packet yet—

Data appears as it arrives. A red border means SHA-256 verification failed. Resend the whole transfer if needed.

How it works

Chirps locate each packet. OFDM sends bytes on many tones using differential phase (DBPSK or DQPSK). Reed–Solomon repairs errors; CRC-16 checks the header and CRC-32 checks the payload. Large transfers use full-size data packets followed by a SHA-256 verification packet. Each multi-packet transfer uses a control byte: its two lowest bits indicate 01 = more data follows, 10 = last data packet (SHA-256 follows), and 11 = SHA-256 verification packet; 00 is reserved. A separate start bit resets the receiver for a new transfer. Single-packet messages keep their original format without a control byte.

Microphone
Not opened
Input level
—
Screen lock
Inactive

Keep both devices close and their pages visible.