UNIVERSITY OF EL SEGUNDO

FIELD INSTRUMENT 01 · 33.9192° N · 118.4165° W

RADIUS/ 90245

A free-space radio bench centered on El Segundo. Move a receiver through the 25-mile field layer. Change the carrier, power, gain, bandwidth, and losses. Watch the geometry become a link budget—and listen when the margin disappears.

Open the field bench
LOCAL REASON 01

Space Systems Command is headquartered in El Segundo. The local engineering culture works in links, interfaces, mission threads, networks, and data flows. This is a small public instrument in that language—not a recruiting brochure.

Primary source · SSC Command Plan ↗
EL SEGUNDO AIRFETCHING
WIND—
CLOUD—
MODEL USECONTEXT ONLY

Live weather is shown but is not inserted into the free-space equations.

THE 25-MILE LAYER

Move one hypothetical link through the field.

The calculator is deterministic and client-side. Nothing is transmitted. No location, settings, or audio leaves this browser.

25 MI
15
5
ES90245
LAX / N INLAND / E SOUTH BAY / S PACIFIC / W

Receiver 4.50 miles from El Segundo at bearing 238°.

STARTING CONDITIONS

A line-of-sight rooftop model with directional gain and an obstruction allowance.

CALCULATED NOW

The answer, with the assumptions still attached.

FREE-SPACE PATH LOSS 124.92 dB

Geometric spreading only. The core reference number.

RECEIVED POWER -82.92 dBm

After combined antenna gain and the entered extra losses.

THERMAL NOISE FLOOR -94.99 dBm

At the selected bandwidth and receiver noise figure.

SNR 12.07 dB

A reference margin above the modeled noise floor.

SHANNON CEILING 81.95 Mb/s

An ideal upper bound—not a modulation or protocol promise.

ONE-WAY LIGHT TIME 24.16 μs

Vacuum propagation only, before any system latency.

MIDPOINT FRESNEL RADIUS 9.67 m

First-zone radius at the path midpoint.

WAVELENGTH 5.17 cm

The physical scale behind the carrier frequency.

SIGNAL TRACE

A tone is not proof.

“Hear the signal” maps modeled SNR to a restrained tone plus noise. It is a sonification, not captured RF, a modem, or a prediction of real packet performance.

METHOD / LIMITS

Useful precisely because it refuses to pretend.

This bench models free-space geometry, thermal noise, and an ideal information ceiling. It does not model terrain, structures, foliage, multipath, polarization mismatch, antenna pattern, hardware linearity, interference, atmospheric absorption, rain fade, Earth curvature, regulation, exposure limits, or installation safety.

EDUCATIONAL REFERENCE ONLY · NOT A SITE SURVEY · NOT SPECTRUM AUTHORIZATION · NOT DEPLOYMENT ADVICE

  1. 01
    Free-space path loss92.45 + 20 log₁₀(d km) + 20 log₁₀(f GHz)
  2. 02
    Received powerPtx + antenna gain − other loss − FSPL
  3. 03
    Noise floor−174 + 10 log₁₀(B Hz) + NF
  4. 04
    Shannon ceilingB × log₂(1 + SNRlinear)
  5. 05
    First Fresnel midpoint√(λ × distance / 4)
  6. 06
    Light timedistance / 299,792,458 m/s

PRIMARY SOURCES

Open the references. Challenge the instrument.

itu-p525ITU-R P.525-5 · Calculation of free-space attenuation

Free-space basic transmission loss.

↗ nist-cNIST · Definitions of SI base units

Exact speed of light in vacuum: 299,792,458 m/s.

↗ ssc-command-planSpace Systems Command · Command Plan

Local context: Space Systems Command is headquartered in El Segundo.

↗ machineRADIUS / 90245 JSON packet

Presets, equations, center, source links, and boundary.

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