The Wide Band Transcorder (WBT) is an inexpensive fully self-contained radio frequency (RF) recording and playback system that is man portable and easily used by both novices and experts.

1. QRC Technologies / 1211 Central Park Boulevard / Fredericksburg, VA 22401, USA / voice: 540.446.2270 / web: www.qrctech.com
27 January 2014
Transfer, sale and/or export or re-export of QRC products, including “deemed export,” is subject to the U.S. Export Control Regulations and Laws, including but not
limited to the Export Administration Regulations (EAR) and International Traffic in Arms Regulations (ITAR). Any transfer, sale, and export or re-export is contingent
strict adherence to and compliance with the EAR and ITAR as appropriate.
Case Study:
UsingWBT to Record & Recreate Interference for
Further Analysis
With RF networks deployed world wide, when a
problem occurs in the field it can be quite
challenging to field the right equipment quickly and
efficiently solving end-user problems while
maximizing customer satisfaction and usage based
revenue.
Wireless systems are proliferating worldwide. A
limiting and key nemesis of wireless systems
providers and RF engineering teams is signal
interference. Interference impedes the coverage
and performance, and degrades the overall
capability of the network and user experience.
According to AT&T, the volume of wireless data is
doubling annually. The smartphones are creating
a chasm between bandwidth supply and demand.
The prediction is an 18-fold increase in mobile data
traffic over the next 5 years. With this growth, the
RF signal environment is becoming much more
complex and problematic which results in signal
interference.
WatchUsRecordtheAirwaves...
Introduction
Challenge–ManagingtheSpectrum
Environmental and US Federal Communications
Commission (FCC) regulations are limiting the
number of base station sites and locations. It is
very common to have multiple towers and more
antennae co-located atop buildings or mountain
UseCase-WBTInterference
Providers must coexist with multiple types of signal
environments of both new technology and existing
systems. These systems include, but are not
limited to, mobile network providers, broadcast
networks TV/radio, paging systems, microwave,
and wireless local area networks (WLANs), all
providing complex signals which have the potential
for interference.
areas and other terrestrial sites within a small
footprint all emitting RF causing and increasing
the potential for signal interference. Also, a
common and inexpensive way to improve cellular
coverage is through the use of a bi-directional
amplifier (BDA). A BDA receives the downlink
signal on the donor antenna and then amplifies
the signal “extending” the coverage for the
operator. When installed correctly, BDA’s are
helpful. When improperly installed, the extremely
high output power of the BDA (~40dBm) can
cause significant interference. The ultimate
consequence is reduced data rates, less
bandwidth consumed and lower user satisfaction.

2. Specifications are Subject to Change and are not Legally Binding. Doc: CS-004 (27 January 2014)
QRC Technologies
1211 Central Park Boulevard, Fredericksburg, VA 22401, USA
web: www.qrctech.com
QRC Sales
voice: 540.446.2270
fax: 540.548.4080
Using WBT to Record & Recreate
Interference for Further Analysis
It was determined at 826.5 MHz the channel
separation of the interference was only a few MHz
apart. The WBT similarly helped to uncover at
852.13 MHz the system tested didn’t appear to
have an external transmit filter.
The WBT recorded the environment and
interference providing the real spectrum for
documenting, lab analysis and repeated testing of
the network. Based on the information and
recordings of the WBT a solution was designed
which reduced the level of interference to an
acceptable level.
The QRC WBT operates like a narrow band
spectrum analyzer. The unit will display a
frequency band of up to 50 MHz or two channels
of 25 MHz or less. The smaller bandwidths are
available for longer recording periods. This
spectrum may then be recorded for a historical or
baseline performance record. Later measure-
ments can be compared to this record for
evidence of degradation or frequency/bandwidth
changes. The unit contains two hot swappable
disk drives (960 MB) that are easy to remove and
store.
For example located atop Abajo Peak in Utah at an
elevation of 11,368’ within 40 yards are eight
separate cell towers all with multiple antennae
emitting spectrum. Recently a prominent mobility
carrier experienced problems and reported
elevated noise at this site primarily in the Gamma
sector of their tower. They were having intermittent
problems with interference affecting the uplink
(receive) frequency of 826.5 MHz and downlink of
852.25 MHz.
The tower is facing a co-located tower atop Abajo
Peak with 800 MHz omni-directional antennas at
approximately the same elevation.
The operator used a valuable tool to help monitor
and isolate the possible interference, QRC
Technologies Wide Band Transcorder® (WBT®).
This dual use recorder can visually examine
portions of the spectrum, record the results and
retransmit the data for either later analysis or
testing for effect.
The WBT allowed the visualization of 12.5 MHz of
spectrum centered at 826.5 MHz and another 12.5
MHz of spectrum centered at 852.25 MHz. The
issue was more pronounced and a far worse
interferer was observed at 852.25 MHz. The
interference was sporadic due to infrequent use
and makes it more difficult to analyze the issue.
However, the WBT with the ability of continuous
recording provided spectrum information and
showed interference from the state owned 800
MHz transmitters.
MitigatingSignalInterference-ManagingtheSpectrum
A comprehensive library can be to document
spectrum performance for future analysis. This
can be done not only for the emitters, but for
areas of the spectrum of concern. Do you have a
low SNR satellite link? Checking and document-
ing the guard bands may be a wise thing to do.
Were there any adjacent signals before? Check
the disk. Preventing creeping interference is a
smart way to prevent future problems.
The ability to retransmit prerecorded signals is
another way to get the jump on potential
problems. Test signals may be generated to
determine any interactions before the installation.
The test signal may be moved to any frequency
within the WBT’s range. The output level is
adjustable and external power amplifiers can
boost the level to any range desired. This
capability is also excellent for the training role.
The ability to transmit recorded files lets future
interference hunters develop their skill set.
WBT can be a vital tool for the interference hunter.
It may be even more important for interference
prevention. It is a one box solution. It is versatile,
capable of many applications, and easy to
operate. Future on board applications will
improve capability. There is a planned application
space designed into the unit for customers to
implement their own applications.