Skip to content
About eSIM Travel Guide

Hi, I’m Sergio.

I’m a telecommunications engineer with 27 years of experience, including hands-on wireless and cellular infrastructure work. I use that background, first-hand travel testing, and detailed research to make eSIM decisions clearer.

Telecommunications Engineer Network · Field Operations · Cellular Infrastructure
27Years in telecommunications
12Years in wireless and cellular infrastructure
40+Countries travelled
3Countries lived and worked in

I created eSIM Travel Guide to help travelers understand mobile connectivity without having to decode provider marketing, roaming terminology, or technical specifications on their own.

From Portugal to the United States and Canada

I was born and educated in Portugal and graduated from ISCTE – University Institute of Lisbon in 1999 with a degree in Telecommunications and Computer Engineering. I began my career working in network and field infrastructure, gaining hands-on experience with the physical systems and network operations that keep people connected.

1999

Portugal

Graduated and began working in telecommunications, network operations, and field infrastructure.

2005

United States

Moved to the United States and spent approximately four years working in telecommunications and network infrastructure.

2009

Canada

Moved to Canada around the winter of 2009 and continued building my career in the Canadian telecommunications industry.

Hands-On Wireless and Cellular Infrastructure Experience

I have worked in telecommunications since 1999 and have 27 years of professional experience as of 2026. For the past 12 years, I have worked in Telecommunications Technician and Field Operations Technician roles supporting wireless and cellular infrastructure.

Field infrastructureMaintaining and troubleshooting cell sites, base stations, data hubs, and central offices.
Network diagnosticsInvestigating hardware failures, fiber-optic connectivity, signal interference, power systems, and network backhaul.
Specialized equipmentWorking with fiber-optic splicers, optical time-domain reflectometers, spectrum analyzers, transmission testers, and digital multimeters.
Network resiliencePerforming preventive maintenance on backup batteries and generators that help keep cellular networks operating during outages.

This experience gives me a practical understanding of how cellular networks operate beyond what appears on a phone screen or coverage map. Living and working in Portugal, the United States, and Canada—and travelling to more than 40 countries—has also given me firsthand experience with mobile networks, roaming systems, SIM cards, and the challenges of staying connected across borders.

What eSIM Travel Guide Is About

eSIM Travel Guide is a separate global publication with deeper coverage of the United States. It is designed to help travelers choose, install, and use mobile connectivity that fits their destination, device, and travel plans.

  • eSIM destination guides organized by country and region
  • Detailed guidance for visitors to the United States
  • Independent eSIM provider reviews and comparisons
  • Device compatibility, installation, activation, and Dual SIM guidance
  • Practical troubleshooting for connection and mobile-data problems
  • Roaming guidance with additional coverage for US carrier customers
Behind the recommendations

How I Test and Research eSIMs

I combine first-hand eSIM testing with detailed provider and carrier research. When I personally test a service, I document the location, device, network, and measurements. When a recommendation is based on research rather than direct testing, I make that distinction clear.

My testing can include stationary use, walking, commuting, driving, and train travel. I use tools including Ookla Speedtest, Opensignal, field-test diagnostics, and CellMapper while keeping individual measurements and real-world mobility observations within their proper evidence limits.

Read the complete testing methodology

A Separate Perspective from eSIMs.ca

I also created eSIMs.ca, which focuses specifically on Canadian readers, Canadian carriers, and trips starting from Canada. eSIM Travel Guide has its own international audience, global destination structure, and stronger emphasis on travel to and from the United States.

Independent, Evidence-Based Guidance

My professional infrastructure work and my independent eSIM testing are separate. The information and opinions published on eSIM Travel Guide reflect my own travel use, documented measurements, professional knowledge, and research. They do not represent or imply endorsement by any current or former employer.