I'm the person who reviews every field test report before it reaches our clients. Roughly 40 reports a week, every week. In 2024 I rejected about 12% of the first submissions, usually for three reasons: a wrong measurement mode, a missed calibration, or an instrument that never matched the job in the first place.
That last one is what this guide is about. Specifically, two Anritsu units I see on a regular basis: the classic Site Master S331B and the 5G Field Master Pro MS2090A. If you're trying to understand what Anritsu Corporation actually makes, what a field analyzer is, and which tool belongs in your truck, here's the five-step checklist I use.
Anritsu Corporation is a Japanese test-and-measurement manufacturer with roots going back to 1895. They build everything from handheld field instruments to benchtop RF testers, optical devices, and network monitoring systems. For telecom engineers, their portable analyzers are the tools you see strapped to tower techs and R&D benches—if you've watched someone sweep a coax run or hunt an interference source, there's a good chance an Anritsu logo was on the screen.
A field analyzer is a portable, battery-powered instrument that measures RF signals and transmission-line health outside the lab. Within that category, two families matter for this discussion:
That distinction is more important than any spec sheet. I've rejected reports from techs who used a cable analyzer to "verify" a signal, and from techs who used a spectrum analyzer to check a feeder line. Wrong class of tool means wrong data, and wrong data means a wasted site visit.
The Site Master S331B is a handheld cable and antenna analyzer covering roughly 25 MHz to 3.3 GHz. It's been in continuous field use for over two decades, and you still see them on crew trucks in 2025 for a reason: they hold calibration well, operators know them inside out, and for DTF and return loss testing on installed lines, they get the job done.
The honest limitation: it isn't a spectrum analyzer. It can't demodulate 5G NR. It won't show you an interfering signal. And its frequency range stops well short of modern microwave bands. If your team's work is purely passive line testing, that's fine. If it isn't, you need more than this tool.
The MS2090A is Anritsu's 5G Field Master Pro. Depending on the option, it covers 9 kHz up to 9, 18, 32, or 44 GHz. It's a real-time spectrum analyzer with a touchscreen interface and 5G NR measurement capability. In practice, that means it can:
It also costs considerably more than an S331B, and calibration plus software options add to the total. I'll get to that in Step 4.
This is the checklist I use when equipping a new team or reviewing a purchase request. It's built for these two Anritsu models, but the logic carries over to any field test gear.
Go through the last ten work orders and categorize them. Not the measurements you'd like to run someday—the ones that show up this month.
Checkpoint: if you can't sort your last ten work orders into those two buckets, you don't have enough data to make a buying decision yet.
"Newer is wider" isn't always the right way to think about coverage. The S331B's 25 MHz to 3.3 GHz span handles most LTE bands and legacy systems, but it doesn't cover many 5G mid-band deployments or microwave backhaul links. The MS2090A, depending on the configuration, covers everything from 9 kHz up to 44 GHz—including the 3.5 GHz range used widely for 5G and mmWave where that's active.
Write your current band table and near-term rollout plan on one page, then check the spec sheet against it.
Checkpoint: if every band you support falls inside the instrument's range, move on. If not, stop here and widen the search.
I once watched a tech drop a Site Master off a scissor lift onto gravel. The case dented. The unit kept sweeping, and the DTF trace matched the baseline from the week before. The S331B is small, runs on a physical keypad, and is easy to handle one-handed on a ladder.
The MS2090A is a larger, heavier tablet-style unit. It's excellent in a truck or an equipment room, and we run them on rooftops too. But with gloves on, at height, it's a handful. That's a real consideration, not a minor one.
Checkpoint: borrow or rent the shortlisted instrument and take it on an actual site visit before you standardize. A day in the field tells you more than a week of spec reviews.
The purchase price is the smallest part of this decision. What typically trips up budget requests:
Checkpoint: require a written calibration quote and a clear software price list before the purchase order goes out.
The step nobody loves, and the one I care about most. Before an instrument gets assigned to a technician, I verify three things:
Checkpoint: if the certificate is missing or expired, the tool doesn't go in the field. Period.
The most frustrating part of this job is the same errors appearing across different teams. You'd think a written measurement procedure would prevent it, but interpretation varies more than it should.
"We always used the spectrum analyzer, so the data must be right." The instrument doesn't know what you intended to measure. Resolution bandwidth, reference level, and calibration state all depend on the operator. I see this failure more often than I'd like, and I do not say that lightly.
"The S331B is obsolete because it's old." This was true years ago when the first-generation Site Masters were compared to newer cable analyzers with much wider sweeps. Today, the S331B is well-characterized, widely documented, and still a defensible choice for return loss and DTF work. Obsolete is not the same as old.
Buying one tool hoping it covers everything. The MS2090A is an excellent spectrum analyzer. It is not a universal replacement for a dedicated cable and antenna analyzer in every team. And no firmware update turns an S331B into something it isn't. Match the toolchain to the work.
What's the best Anritsu field analyzer? There isn't one. There's the right tool for your specific work, and there's everything else.
If your team measures return loss, VSWR, and cable loss on installed lines, I'd recommend the S331B without hesitation. It's proven, still supported, and a solid calibrated unit remains a very reasonable investment. If your work involves spectrum management, interference hunting, or 5G NR verification—especially on bands like n93 or mid-band deployments—the MS2090A is the stronger instrument.
If you're somewhere in between, that's exactly when this checklist earns its keep. Work through the five steps, get real quotes, and choose based on the measurements you can prove you'll be running.
Specifications referenced from publicly available Anritsu product documentation, January 2025. Verify current models, options, and pricing with Anritsu Corporation before making a purchase decision.