Delivering leading solutions for today's field and maintenance challenges
With over 20 years leading the way in handheld testing Anritsu has a well earned reputation for superior measurements in not so superior conditions. learn more about the very latest handheld testing technology.
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Best Practices to Prevent PIM
Passive Intermodulation (PIM) is a serious issue for cellular operators looking to maximize their network’s
reliability, data rate, capacity, and return on investment. High-speed digital data communications make PIM
testing critical. As cell usage and throughput grows, the peak power produced by the new digital modulations
increases dramatically, contributing heavily to PIM problems, and making it a measurement that field
technicians need to understand.
There are several best practices to avoid PIM when working with precision RF cables and connectors.
Here are some techniques to remember when out in the field:
With the connectors apart, inspect them for physical
damage. The center connector should not be loose,
and should have no visible dents or scratches. Use
a small magnifying lens to conduct this inspection.
Any damage or contamination may allow micro
arcing or the diode effect to occur, causing some
level of PIM. This inspection will also help spot
sources of VSWR problems.
Use a cotton swab, low-pressure air, Isopropyl
alcohol, and a toothpick to clean connectors before
re-assembly. Here’s an easy three-step process:
- Remove loose particles by using low-pressure
compressed air. A toothpick is useful to remove any
small particles that the air does not remove.
- Use Isopropyl alcohol on cotton swabs to clean the
rest of the surface. Don’t use too much Isopropyl
alcohol, as it may melt plastic parts.
- Use the low-pressure air again to remove any
remaining small particles and dry the surface.
Proper torque on the connector will not only help
minimize PIM, it’s required. Low torque will create
gaps and PIM from the center connector. High torque
will damage the center connector, again, causing PIM.
If it is required to connect and disconnect the same
joints several times, mating cycles may be an issue.
Manufacturers specify the number of mating cycles
they can guarantee. Generally, it’s important to check
with each manufacturer for torque specifications, as
they vary slightly depending on the situation.
Questions and Answers
Question: Does Anritsu offer the ability to upload traces
acquired in the field for online delivery and viewing?
Answer: Our SweepMasters DIRECT (available to S331L users only) is an easy-to-use online trace delivery system
that allows you to capture, upload and deliver traces. When
you are ready to deliver results, links to the organized
traces, as well as a .pdf report, are sent via email to the
specified project management company or wireless carrier.
Passwords prevent unauthorized access to the data, adding a
level of security to the system.
Question: What tools on the Spectrum Master™ help measure intermittent interfering signals?
Answer: If the interfering signal is periodic – or bursty – it
is helpful to use the “Max-Hold” on Trace B, while keeping
Trace A in normal view. For signals that are intermittent over
a long period, you can use the “Save-on Event,” coupled with
an a limit line that is several dB above the expected signal
levels. This limit line can be automatically created using Limit
Envelope. Burst Detect can be very helpful to find intermittent
interferers. See the following article. Once detected, the trace
is saved for later analysis. We also offer Spectrogram, an
excellent tool that shows how signals change over time. See
"Tools of the Trade" for Burst Detect, a way to easily see
pulsed or bursty signals."
Question: Can I use the same instrument to conduct PIM tests and line sweeps?
Answer: Yes, our Site Master™, Cell Master™, and BTS Master™ can conduct both line sweeps and PIM tests, when they are configured with our PIM Master™. This ability saves time and simplifies measurements, as an installation contractor or technician only has to learn how to use one instrument to make all related antenna measurements for linearity and impedance testing.
|It’s important to characterize an interfering signal before disconnecting from the receiver’s pre-filter or test port.
Adjust your spectrum analyzer's pre-amp, reference level, span, and resolution bandwidth controls to get the best
view of the signal. Observe the signal’s shape, bandwidth, and behavior over time. Look for frequency drift, amplitude
changes, and frequency hopping. For a bursty signal, use Burst Detect to easily see them. For intermittent signals
with a long time between appearances, use the unique "Save on Event" capability found in the save menu.
Locate Narrow Signals More Accurately and Easily with Burst
Anritsu Company’s industry-leading MS272xC Spectrum Master™ series has taken another leap forward in providing
users with test ability necessary to accurately measure today’s wireless networks. A new burst detect capability for
the MS272xC handheld spectrum analyzers allows field engineers and technicians to easily find pulsed or bursty
signals that may cause interference and adversely affect network performance.
A key benefit of the burst detection feature is that the MS272xC can make up to 20,000 measurements per second
with the enhancement. This is thousands of times faster than a normal FFT, and allows users to see 200 microsecond
pulse trains every time. The result is that users can find burst signals, including those generated by improperly
installed cell phone boosters, much more easily than before.
|Combining 30 analyzers in a single instrument that offers leading
performance, including resolution bandwidths from 1 Hz to 10 MHz,
advanced triggering, and a 30 MHz zero-span IF output, the MS272xC
family provides wireless professionals with the analysis capability
necessary to meet the most demanding measurements. Whether
your application is spectrum monitoring, hidden signal detection,
RF/microwave signal measurements, microwave backhaul testing or
cellular signal measurements, the Spectrum Master MS272xC family
has tools to make the job easier and more productive.
Mission Impossible a Success Thanks
to BTS Master
|The mission: integrate 92 base stations, test and sweep 552 antenna systems, and ensure 300 T1 lines
operate properly all over the United States in just one year. It may have proven impossible for some but for
Mike Moderski and his team of six field engineers - each equipped with a MT8222A BTS Master™ - mission
impossible became mission accomplished.
Moderski and his team had the assignment of helping deploy and install an Air to Ground (ATG)
communications systems for commercial and business aircraft. The national system had to have clear line of
site to the horizon, meaning most transmitter sites had to be installed on the highest mountain peaks across
the country. Some sites, however, were at the other extreme.
“The diverse geography was no match for our test gear. From one-foot below sea level to 14,000 feet in
a blinding blizzard, in freezing temperatures to the sun and heat of the dessert, the Anritsu equipment
withstood it all,” explained Moderski.
|“What Mother Nature dished out was nothing
compared to the manmade hazards. After
traveling over 100,000 miles, countless TSA
screenings, airport after airport baggage handling,
hundreds of shipments, and even privately
chartered aircraft, the Anritsu MT8222A continued
to perform like new.”
Of course, the BTS Master had to deliver
excellent test results, as well. Due to the fact
the band for the ATG system sat right above
the cellular band, it was very susceptible to
interference. Initial site assessment of RF
conditions was key to the network’s success.
Moderski and crew used the MT8222A to identify
and locate any source of interference so it could
be mitigated quickly.
For Moderski, it was the combination of performance and durability that impressed him most
during the year-long mission. “We were chased by Elk, stalked by a mountain lion, ran from bears
and snakes, swatted wasps, mosquitos, spiders and even had one site infested with rats. Our test
equipment was dropped, kicked and bounced around all type of vehicles and in all types of conditions
across the country. Temperature changes and rough handling didn’t affect the MT8222A performance.
It delivered time after time!”