# Read propagation algorithm documentation

The scoring algorithm for amateur-radio microwave propagation (902 MHz – 241 GHz) is documented in long-form markdown, covering factor weights, band-specific configurations, ITU-R atmospheric models, and calibration dataset composition.

## Endpoint

```
GET https://prop.w5isp.com/algo
```

The default response is HTML. Send `Accept: text/markdown` to receive the raw markdown source directly:

```
GET https://prop.w5isp.com/algo
Accept: text/markdown
```

Response: `Content-Type: text/markdown; charset=utf-8`. An `x-markdown-tokens` header gives a rough token-count estimate for context-window planning.

## Content summary

- Scoring methodology: 10 weighted factors combining to a 0–100 composite score per grid point per band.
- Factor weights (humidity 13.6 %, time of day 5.0 %, T-Td depression 9.8 %, refractivity 10.5 %, sky 8.0 %, season 11.1 %, wind 8.0 %, rain 13.6 %, pressure 10.3 %, PWAT 11.3 %) recalibrated 2026-04-11 via gradient descent against 57,488 tropospheric QSOs.
- Band-dependent humidity effect: beneficial at 10 GHz (refractivity gradients), harmful at 24 GHz+ (gaseous absorption).
- ITU-R model references: P.838-3 (rain attenuation), P.526-16 (diffraction), P.676 (gaseous absorption).
- Terrain analysis: 97.2 % of all analysed QSO paths are terrain-blocked; atmospheric ducting and refraction are the primary enabling mechanisms.
- Calibration dataset: 58 k+ QSOs, HRRR atmospheric profiles, RAOB soundings, IEMRE gridded observations, SRTM terrain, and commercial link SNMP polling at 11/24/68 GHz.