Cross Building Isolation Test
Typically, the isolation test ensures adequate electrical separation between the indoor antenna network and the donor antenna. The cross building isolation ensures adequate isolation between one building donor and a different buildings indoor antenna network. When a new BDA system is installed in a building that is close to one or more existing buildings that are also using an ERCES for in-building enhancement (e.g. within ~300 feet), testing is recommended to ensure they are sufficiently isolated. The uplink from one system could activate the uplink in the second system causing interference. The Cross Building Isolation Test verifies there is no signal from one system activating the other. This can occur in campus environments, urban cities, or even shopping centers. The AHJ should maintain a database of existing systems and help facilitate this testing when required.
The configuration uses the Uplink Isolation configuration with different diagrams. Unless you have access to the existing building BDAs to use a test channel, it is easier to key up on a test radio using the live system from a lobby or general access area. You will need to be able to distinguish your traffic from all others and be sure you are driving the BDA to full power output.
Cross Building Isolation Procedure
There are 2 methods with separate diagrams, using a test transmitter and using a radio. If using a radio you will need to group all the UL channels for your system and monitor the power while maintaining communication with the tester to ensure you are looking at the right channel. This procedure is directly quoted from a jurisdiction enforcing the test.
Minimum Distance to other ERRCS/BDA/Signal Boosters Any building with an ERRCS installation that is located within 300 feet of any other existing building with an ERRCS shall be considered a “nearby ERRCS”. A cross-isolation test shall be performed between the new ERRCS and any other “nearby ERRCS” within 300 feet. The distance shall be measured between the location of donor antenna and the closest exterior wall of each building, and vice versa.
Cross-Isolation There shall be at least 100dB isolation between any ERRCS output and any other nearby ERRCS input. If isolation is less than 100dB, the new ERRCS installation shall be modified until the cross-isolation between ERRCS is within spec. Relocating or adjusting a poorly positioned donor antenna or service antenna(s), or to replace omni-directional service antennas near exterior walls with directional antennas is preferred. Attenuators at the new ERRCS installation headend may be used to increase isolation.
Procedure
1. Select your test frequency from the list or add your test frequency.
2. Set BDA gain to 80dB and Target isolation to 20dB. This will ensure the 100dB isolation for pass/fail target.
3. Set injected power to either the power of your transmitter or the power output of your radio(at least a 0dBm but +10dBm preferred). The device will be generating at the location of the existing building donor antenna.
4. Connect the IBFLEX to the DAS of the new building and record the measurement.
Uplink cross-isolation test (1) At any other nearby ERRCS, a test signal shall be injected* at the BDA uplink input that is sufficient to drive the uplink output to its peak ERP (+24dBm per channel). *An approved test radio may be keyed within 10 feet of the hot antenna of nearby ERRCS. (2) At the new ERRCS headend, the uplink input signal level to the BDA shall be measured. (3) If the uplink input signal received at the new ERRCS exceeds the required uplink squelch level (>-75dBm), then the installer at the new ERRCS location shall modify the service antenna or donor antenna configuration or add external attenuation to the UL input until the signal received at the new ERRCS is below -75dBm.
EXAMPLE: At Building A (pre-existing “nearby ERRCS”), the installer injects a signal into its uplink input (user keys a portable within 10 feet of the “hot antenna”). Building B (a new ERRCS) receives a signal of -70dBm at its uplink input (from Building A), which exceeds the required squelch level (-75dBm). At Building B, the installer reconfigures the location of several service antennas placed near windows or adds 10dB of attenuation to its uplink input. On retest, Building B now receives a signal of -80dBm, which is below the required uplink squelch threshold (-75dBm). Building B now complies with the cross-isolation requirement.
Procedure
1. Use the Spectrum Noise Analysis to capture this event.
2. In configuration select your start and stop frequencies for your test channel and resolution bandwidth.
3. Start the Spectrum Noise analysis.
4. Key the radio at the near location or generate to cause maximum output from the BDA.
5. Add to report.
6. Review and set the pass/fail for the Noise Analysis Result. Pass if the signal was less than -75dBm, fail if greater. Add attenuation or modify the indoor antenna network to achieve a Pass.