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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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Solving RF Interference Problems

As more and more diverse uses for the radio spectrum emerge, the number of signals that may potentially cause interference increases dramatically. There are literally millions of radiators in operation at any one time in relatively small geographic areas. Detecting and correcting interference problems has become more important because of the crowded RF spectrum. It has also become more difficult, if you don’t use the correct measurement tools.
Finding Interference
Put on your detective hat and think in ways outside of usual linear thinking patterns. Like any other kind of troubleshooting, there is no clue that should be discarded too quickly. There may be patterns to interference that can give hints as to the source of the problem. Pay attention to the time of day, day of the week, time of the month and time of the year as well as temperature, humidity, precipitation, etc.


 
MS2720T
Sometimes interference is caused by fundamental overload caused by a nearby large (perhaps mobile) signal. Such interference causes a reduction in the effective sensitivity of the receiver, due to saturation of the front end mixer. This can be difficult to solve if the interfering emitter is on the air only sporadically. Clues such as occasional reduction in the coverage area, dropped calls for cellular systems and the inability of distant users of a land mobile system to communicate through a repeater in locations where they normally can do so can help you troubleshoot this sort of problem.
If you determine that you have fundamental overload interference, about the only way to solve the problem is by filtering to reduce the amplitude of the interfering signal enough that the sensitivity of your receiver isn’t significantly degraded. The filter could be a bandpass filter that covers your intended receiving frequency range or a notch filter centered on the interfering signal, or both.
Continuous interference is the easiest to resolve. Use a directional antenna to track down signals that are there all the time. Then, you can locate the signal that doesn’t belong and track it to the source. Detecting intermittent emitters requires patience and dedication. Fortunately there are measurement tools now available that reduce the need to unblinkingly stare at a spectrum analyzer screen so you won’t miss the intermittent signal when it does occur. In the MS2721B, MS2723B and MS2724B, you can employ “save on event” to capture suspect signals.
 

Questions and Answers

Question: On occasion, the noise floor on my MS2711D changes value by 25 dB. Why is that?

Answer: The MS2711D, S332D and the MT8212B have a feature called “dynamic attenuation” that monitors the overall signal levels into the instrument. If there are no strong signals, it removes all input attenuation and turns on the preamplifier. When strong signals occur, it immediately turns off the preamplifier and, if necessary adds input attenuation to avoid mixer saturation. The preamplifier has a gain of approximately 25 dB, which is why the noise floor changes by 25 dB when it is inserted or removed from the signal path.

Question: Does the Cell Master™ MT8212B require GPS when building CDMA PN searches?

Answer: Yes, the Cell Master MT8212B does require GPS to do in-building CDMA PN searches. This requirement is not due to limitations in the test equipment but is driven by the CDMA technology, which requires a sync source.

Question: What is the difference between an OSL calibration and FlexCal?

Answer:With OSL, you have to calibrate each time you change the frequency range. FlexCal allows you to change the frequency range without performing another calibration. FlexCal is great for troubleshooting purposes. The accuracy can be affected if your span is really narrow so for optimum accuracy, it is recommended to use the OSL calibration.

Question: Can I sweep antennas close to another RF source?

Answer: Yes but you need to be very careful that the RF from the other source is not going to exceed the 20 dBm max on the RF port. Power in excess of 20 dBm can result in damage to the unit.

 

Test Tip

The conventional CW diode detector is no longer the best choice for conducting power measurements on signals using complex modulation schemes. A true RMS sensor is needed to measure the channel power of digitally modulated signals accurately.
 

New Platform Redefines Wireless Field Test

 
MT8221B
 

Field engineers, technicians and other personnel responsible for deploying, installing, and maintaining 2G, 3G, and WiMAX networks now have better tools to work with. Anritsu has developed the E platform that features integrated functionality in a robust, lightweight, field-proven design that allows measurements to be made accurately, reliably and faster than ever before.
The new platform is designed into the Site Master™, Spectrum Master™, BTS Master™ and Cell Master™ analyzers. An intuitive user interface, high-quality construction, and unmatched price/performance are trademarks of the new analyzers. Other enhancements of the E series include wider frequency coverage, faster sweep speeds, larger 8.4-inch touch screen display, more communications ports, and a larger internal memory. In addition to providing the technology necessary for today’s field testing requirements, Anritsu is offering certified training and world-class support.

 
The new analyzer family can reduce both capital equipment and operational expenses because of its multifunctional capabilities. Ease of use and automated reporting capabilities boots efficiency in the field as well as the office. The high performance of all the analyzers allows for greater confidence in measurement results, reduced measurement times, and gives users the ability to detect small problems before they become costly network failures. Ruggedly designed, the analyzers can withstand the roughest field conditions and activities.
 

Anritsu Provides Total Solution to Forward Link

   
Roy Anderson, Director of Wireless Services – West for Forward Link, sees one parallel between his company and Anritsu – a commitment to the wireless field market. “It (the wireless field test market) is part of Anritsu’s core. Other manufacturers look at it opportunistically so they don’t provide the same support, training, and products that are offered by Anritsu.”
For Anderson, that commitment is important, and it’s what separates Anritsu from everyone else. “Anritsu is the one major manufacturer who has stuck with the marketplace. You can see it in their product breath. It’s obvious they are committed.”
One of those products is quickly becoming a favorite of Anderson. He has been using the BTS Master for a few months and has found it be everything he needs to conduct the gamut of tests required in the field. Anderson uses the handheld base station analyzer to conduct coverage mapping and spectral validation, as well as to make IF and demodulation measurements. One of the key benefits, according to Anderson, is all the options available for the BTS Master. This flexibility allows him to add measurement capability as needed.
“In the past, we would have been faced with carrying around five different instruments. Plus, the design makes is much more affordable to add test capabilities,” said Anderson.
Another benefit is the compact design and ruggedness of the BTS Master. Anderson and his team of three RF engineers have to conduct measurements virtually everywhere, from inside a building to on a mountain in the middle of nowhere. That’s the life of someone who works for Forward Link, a company that helps wireless network operators solve their toughest RF problems.
“I like the size of the BTS Master. It’s also highly accurate for a portable test instrument. These are crucial elements, considering the environment in which we work,” explained Anderson, a 20-year veteran of the wireless market. “It’s a good solid product; exactly what we need.”
The BTS Master measures 315 x 211 x 94 mm and only weighs 4.9 kg. It has best in class Displayed Average Noise Level of typically < -153 dBm in a 10 Hz resolution bandwidth at 1 GHz.


 
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