Author Archives: Gregory Murphy

Pulling the GPS antenna is not a fault. It is a controlled experiment, and like any experiment it is only worth running if you decide in advance what you are measuring, what you are measuring it against, and what statistic you will report. The 70 MHz carrier in your modem or upconverter is not the… Read More: Pulling the GPS Antenna on Purpose: Measuring GPSDO Holdover Drift… »

Editorial note: This publication and Quirky Cotton Collective share an owner. I spend a lot of time looking at spectrum analyzers. The good ones have a trace that sits flat, a noise floor that doesn’t wander, and a marker that lands exactly where you expect it. The bad ones have spurs. You learn to spot… Read More: The ‘Meh’ Shirt: A Study in Visual Loudness and Dismissive… »

An outdoor upconverter that fails only around local solar noon is not a propagation problem. It is a thermal problem with a clock. The sun is a 1.36 kW/m² broadband source at the top of the atmosphere, and at sea level on a clear day the direct-beam irradiance is roughly 1 kW/m², with a spectral… Read More: The Fault That Only Appears at Solar Noon: Localizing a… »

Satellite link availability is the percentage of time a communications path meets its required bit error rate, carrier-to-noise ratio, or frame error rate. It is not a marketing number. It is a statistical statement about rain fade, scintillation, equipment degradation, and interference. For C-band through Ka-band commercial, government, and deep-space systems, availability calculations drive antenna… Read More: Why Satellite Link Availability Calculations Need Real Data »

Mobility satellite links are RF paths that have to hold lock, timing, and spectral discipline while the terminal is moving. The motion can be slow — a maritime VSAT rolling through a few degrees of pitch — or fast, like a low-earth-orbit (LEO) tracking antenna on an aircraft crossing a beam boundary every 90 seconds.… Read More: How to Design Satellite Links for Mobility Applications »

Satellite interference mitigation is the discipline of identifying, locating, and eliminating unwanted RF energy that degrades or denies service on a satellite link. It sits at the intersection of spectrum monitoring, carrier monitoring, geolocation, and operational coordination. For ground segment engineers working C-band through Ka-band, interference is not an anomaly—it is a recurring operational condition.… Read More: The Best Approach to Satellite Interference Mitigation »

Forward error correction, or FEC, is the deliberate addition of structured redundancy to a digital bitstream so a receiver can detect and correct symbol errors without asking the transmitter for a retransmission. On a satellite link, where one-way delays run from roughly 120 ms for LEO to more than 500 ms for GEO, and where… Read More: Why Forward Error Correction Is Not Optional in Satellite Links »

If you’re building or upgrading a satellite ground segment, the modem is where most of your link budget either survives contact with reality or quietly falls apart. A satellite modem converts digital data into an IF or L-band signal for the upconverter, then reverses the process on the receive side. It sits between your terrestrial… Read More: How to Select the Right Satellite Modem for Your Use… »