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Handheld Users Group

Handheld Users Group

Delivering leading solutions for today's field and maintenance challenges

Interference hunter

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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Why PIM Measurements Are Important

High-speed digital data communications used in today’s wireless networks have made passive intermodulation (PIM) testing critical. As cell usage and throughput grows, the peak power produced by new digital modulations increases dramatically, contributing heavily to PIM problems.

Distance-to-PIM Screen
PIM lowers the reliability, capacity and data rate of cellular systems by limiting the receive sensitivity. Indications of PIM include receive-noise-floor-diversity-imbalance and high noise floors. Other signs include shorter average call duration, higher dropped call rates, lower data rates, and lower call volume.
Two or more strong signals and a nonlinear junction create passive intermodulation. Strong signals normally come from transmitters sharing an antenna run, transmitters using adjacent antennas, or nearby towers with conflicting antenna patterns. Damaged or poorly torqued RF connections, contamination, fatigue breaks, cold solder joints, and corrosion can create nonlinear junctions. In addition, nearby corroded objects, such as fences, barn roofs or rusty bolts, can cause PIM. This is referred to as “Rusty Bolt Effect.” PIM often appears as poor statistics from the affected sector. One of the first and most direct indications can be seen in cells with two receive paths. If the noise floor is not equal between the two paths, the cause is likely PIM generated inside the noisy receive path, a condition called Receive Diversity Noise Floor Imbalance.

Reflective PIM Testing
Reverse, or reflective, testing is the most commonly used PIM test. Two signals are sent to an antenna and the same test port is used to capture and measure passive intermodulation. Because reflective PIM testing is affected by the electrical length of the antenna cable, results may not be accurate at fixed frequencies. Reverse PIM tests should be done while sweeping one of the frequencies to avoid unintentional partial error signal cancelation. Another option is to change one of the test frequencies to see how the result varies.

Forward PIM Testing
A forward PIM test can be performed in two ways – using filter networks on the output of a device under test (DUT) or an external antenna measuring propagated signals, such as an antenna in an anechoic chamber. This test can be very handy when trying to find external materials causing PIM, such as loose flashing or other metalwork used in building construction.

PIM testing is becoming more critical as cellular systems age and the carrier count increases. A cell site constructed with PIM in mind will cost less to maintain over time, and show cleaner performance than similar sites that were not PIM tested.


Questions and Answers

Question: How can I display spectrum analysis measurements on a map?

Answer: Spectrum analyzer measurements made using a BTS Master™ or Spectrum Master™ with the GPS receiver turned ON can be mapped using Master Software Tools, if Microsoft MapPoint is installed in your computer. After measurements are transferred to your computer, you should see a Measurement Map selection. This automatically opens Microsoft MapPoint within Master Software Tools. Using the Local Tab on the left, navigate to the folder containing the saved measurements. Select all the measurements and drag them to the (+) sign at the bottom left corner of the map screen.

Question: What is the formula that relates Ec and CPICH on WCDMA/HSPDA Over-the-Air measurements?

Answer: Ec is defined as the chip energy for PCPICH and is determined by multiplying CPICH by the chip time. Ec = CPICH + 10*log10(Chip Time) or Ec = CPICH - 65.84 dB

Question: What is the difference between line sweeping and PIM testing?

Answer: Line sweep testing and PIM are very different tests. Both are very important and accurately measure a cell site’s ability to provide service and perform optimally. Line sweeping measures the signal losses and reflections of the transmission system (impedance matching). PIM testing is a measure of construction quality (linearity); poor quality will result in self-interference. Remember, a quality transmission line is not relevant unless accompanied by comprehensive line sweep tests and PIM tests.


Test Tip

There are several best practices to follow when working with precision RF cables and connectors to help reduce PIM. It is important to keep the connecters clean, avoid distorting the connector, and keep the connector center conductor undamaged.

New PIM Master Addresses 850 MHz Cellular Band


Anritsu introduces the MW8208A PIM Master™, a comprehensive trouble-finding tool that allows field technicians and engineers to accurately and quickly locate the source of passive intermodulation (PIM), whether it is in the base station antenna system or in the surrounding environment. The latest member of Anritsu’s innovative PIM Master family, the MW82119A brings the inherent advantages of Anritsu’s patented Distance-to-PIM™ technology to 850 MHz cellular band applications.
With the MW82119A PIM Master, users can uncover the distance and relative magnitude of all static PIM faults simultaneously, including those resulting from connectors that are dirty, corroded, and over-torqued, as well as microscopic arcing connectors. PIM Master can also accurately locate PIM outside the antenna system – the only test solution that can do so – thanks to Distance-to-PIM. This proprietary technology helps eliminate one of the biggest problems facing wireless network deployment and operation today.

The MW82119A generates two high-power tones in the transmit band of a base station and can measure the 3rd, 5th, and 7th order intermodulation products in the receive band coming down the same cable. Another advantage is its 40 W testing, compared to alternative methods that only measure at 20 W. Utilizing 40 Watts simulates real-world power that activates the PIM that might not otherwise be activated by 20 Watt systems.

Handheld Analyzers Rise above Challenges Posed by Alaskan Mountains

Alaska is known for its picturesque mountain ranges that stretch as high as the sky and as long as the eye can see. Many visit those mountains for fun-filled ski runs or fishing. For others, like James McCulloch, it’s all business. Instead of skis and a fishing pole, he carries Anritsu Site Master™ and Spectrum Master™ handheld analyzers, and he wouldn’t have it any other way.
The Anritsu analyzers come in handy for a number of reasons, according to James. “The dependability and light weight of the Spectrum Master and Site Master are necessities in my job. They also handle the cold weather as well as we do.”
James relies on the Anritsu instruments for other reasons, as well. The accuracy of the instruments helps him locate faults quickly, and the “tech friendliness” is a benefit to making measurements fast and easy.
One experience in which all the advantages of the Anritsu handheld analyzers were necessary was when James visited Bench Peak, which climbs 4,980 feet above sea level. The summit is only accessible via helicopter, which means James had to travel light. The small size and light weight of the instruments were a big plus for him. And since this particular visit was in the dead of winter and James was greeted by deep snow, high winds, and temperatures that fell all the way down to -40° F, the instruments’ field-proven design was a necessity.
When James arrived at the site, he could see he was in for an interesting day. Snow around the microwave dishes had compacted to such a level that the signal had dropped. Using his trusty Anritsu instruments, James was able to accurately sweep the waveguide of a microwave dish, determine why the site went off air, and get it back up and operating.
It was just another day at the office for James. When he was done, he took the trip back in the helicopter, waiting for the next call.
Yosemite park 

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