# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/DbojbkLyJdE
- **Gondola URL:** https://gondola.cc/posts/68785334-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/83eeea5e41.jpg
- **Posted:** 2026-08-04T21:43:08.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

Bluetooth works by running away from interference sixteen hundred times a second.

Every Bluetooth device operates in the 2.4 GHz ISM band, 2.400 to 2.4835 GHz. It is unlicensed, which means it is crowded. Wi-Fi is there. Microwave ovens leak there. Baby monitors, cordless phones and Zigbee sensors share the same spectrum. Rather than fight for a clear channel, Bluetooth refuses to sit still.

Classic Bluetooth divides the band into 79 channels of 1 MHz each. The connection hops between them 1600 times per second, changing frequency every 625 microseconds. Both devices follow the same pseudo-random hopping sequence, derived from the clock and address of the device acting as master. To anyone else listening, the transmission is brief noise scattered across the band. To the paired device, it is a coherent conversation.

Adaptive Frequency Hopping refines this. The radio maps which channels are congested, usually those occupied by Wi-Fi, and removes them from the sequence entirely.

Bluetooth Low Energy takes a different approach:

- 40 channels of 2 MHz instead of 79 of 1 MHz
- Three dedicated advertising channels, numbered 37, 38 and 39
- Those three sit precisely in the gaps between Wi-Fi channels 1, 6 and 11
- Connections stay dormant between short bursts of data, drawing microamps

Data is carried by Gaussian Frequency Shift Keying. The carrier is nudged up in frequency for a one and down for a zero, the transitions smoothed by a Gaussian filter to stop the signal bleeding into neighbouring channels.

Pairing is a cryptographic handshake. Modern devices use elliptic curve Diffie-Hellman to agree a shared secret over an open channel, then derive a link key that survives disconnection.

The name comes from Harald Bluetooth, the tenth century Danish king who united warring tribes. The logo is his initials in Younger Futhark runes.

Some problems are best solved by never staying in one place long enough to be hit.

#stemantics #bluetooth #rfengineering #wirelesstech #electronics

## Stats

- **Views:** 672,775
- **Likes:** 91,140
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- **Comments:** 275

## Tags

electronics, rfengineering, wirelesstech, bluetooth, stemantics

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