Initial Survey and System Planning

Initial Survey

An initial survey needs to be done to determine if the signal enhancement is required. If it is required, the next step will be to measure the in-building signal levels to identify the areas which need signal enhancement. Typically, only part of the building will need coverage enhancement, such as below-grade levels and lower floors in the high-rise. Upper floors usually either do not need enhancement at all or only require partial enhancement in the middle of the building or the side of the building that is facing opposite side of the radio repeater donor site.

The building must be sufficiently complete for the initial survey: all floors, walls, and roof shall be constructed. The survey is typically done just before electrical rough-in wiring starts. If the survey is done too early an inaccurate reading will result, if done too late the electrical work and wiring become very difficult with walls, ceilings and other obstructions in place.

Before arriving on the job site, the technician who is doing the survey needs to review the floor plans and needs to prepare floor plan printouts and note the signal measurement locations.

Also, the technician needs to prepare the test equipment – this usually means programming the hand-held portable radio to the AHJ frequencies.

Portable Radio Programming Software

Please click on the icon below to download Tait portable radio programming software.

Portable Radio Programming Procedure

Notification of Testing

Radio channel users (i.e fire department, police department) must be notified if the survey technician will be transmitting on the channel (i.e to key up the analog repeater). We recommend calling the AHJ ahead of time to get a permission for the test. The technician must be very careful not to transmit or “key up” the portable radio while the radio channel is being used during an active emergency and also not to transmit over other users. Interfering with public safety communications is a serious offense.

If the survey is done just by monitoring the on-channel activity or the control channel transmission and there is no need to transmit at all, then there is no need to notify the fire department.

Survey Using a Portable Radio

1. The survey is done by a qualified and FCC GROL licensed BDA technician using a handheld radio with calibrated RSSI (received signal strength) indications programmed with the frequency channel information of the desired radio coverage.

   1. The Tait / Harris TP9400 portable radio (sold by RSI) provides an RSSI feature and can be programmed such that the RSSI is indicated on the radio display by selecting:

      1. Menu > Radio settings > Display settings > RSSI

2. The AHJ provides the radio frequencies and programming information to the survey technician.

3. Testing is done on conventional repeater systems by momentary key-up and listening for repeater tail by looking at the RSSI reading on the portable radio.

4. With a trunked system the control channel is programmed and you may passively listen to the data and take RSSI readings without having to key-up into the system. The trunked control channel is always actively transmitting.

Site Survey

1. It is good practice to start in front of the building where a fire department may pull up and stage an incident command post. Consult with AHJ.

2. From the front, start in the lowest part of the building:

   1. Basements

   2. Sub-basements

   3. Garages

3. You may want to take more readings in critical ares of the building. Specifically look for:

   1. Machine rooms

   2. Electrical rooms

   3. Stairways

   4. Any other areas that may inhibit radio coverage

4. Signal readings are noted on the floor plan. The annotated survey report is then forwarded to the system design engineer.

   1. Using a different colored ink for different radio channel readings is helpful (i.e. Red ink for fire readings and blue ink for police readings)

5. Work your way up through the building.

   1. Take at least 20 readings per floor. Pay particular attention to mechanical and electrical rooms, stairways and out of the way areas.

   2. Make note of proposed equipment locations, cable risers, chases, structure status, structure build materials and ceiling types (drop, hard or other types).

   3. Look for existing or proposed roof penetrations for donor antenna.

6. Nearing the top of the building make a note of a possible BDA location.

   1. The BDA should be located on an upper floor of the building and should be located in a fire rated space, connecting to a fire rated riser shaft.

   2. It is necessary to keep the donor antenna and DAS cabling separate from each other as much as practical to keep RF feedback to a minimum.

7. Make your way to the roof and take a signal reading at the spot where the donor antenna is to be located.

   1. Take readings in arcs of compass points to verify the direction of the repeater and thus the ultimate orientation and location of the roof donor antenna.

   2. It is important to place the donor antenna on end of the roof that faces the desired repeater site in order to simplify the installation and to obtain maximum signal separation from DAS.

8. Accomplish all this with the help of the electrical contractor or somebody who is familiar with the building, electrical rooms, risers and cable paths.
   

Path Loss Testing

Path Loss Testing is always recommended, especially on older buildings that need to be retrofitted.

For new construction projects, if good documentation is provided, path loss testing may not be necessary. Please consult with your project manager if path loss testing is required for your specific project.

Please click the icon below to download the Path Loss Testing Procedure: