SWM7000 2.4 GHz Wireless Microphone System Application and Troubleshooting Guide Table of Contents 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Dropouts RF Interference Sound Quality Sabine Remote Computer Control Battery Charging System Receiver Transmitter Sabine Remote Software Upgrading your receiver firmware and remote control software Digital Audio Dip Switches Contacting Customer Service ******************************************************************** 1. Dropouts 1.1. What causes dropouts? Wireless microphone systems are vulnerable to dropouts, (momentary loss of audio) and it is often difficult to pinpoint the exact cause of the problem. Dropouts can be caused by improper antenna positioning, defective antenna cabling, a problem with the transmitter, a problem with the receiver, a problem with the sound system. Interference with other RF sources almost never causes dropouts but it can cause sputtering and ticking in the audio. If you are experiencing dropouts, consider interference as a last resort. We recommend the following steps to quickly zero in on the problem. 1.2. Upgrade your receiver firmware. The first step is always to be certain that you have installed the latest versions of the SWM7000 receiver firmware and Remote software. See the Sabine Remote Software section below. 1.3. Is the problem with the sound system? Plug a wired mic into the audio cable plugged into the back of the receiver. If there are still dropouts, you know the problem is downstream of your wireless mic. If dropouts stop, you know the problem is with your wireless mic. 1.4. Problem with the antennas. Improper antenna positioning is probably the most common cause of dropouts. The output power of wireless microphones is limited by governmental agencies to reduce the chances that transmitters in a neighborhood will interfere with each other. The downside is that your antennas 1 of 13 must be carefully placed in order to pick up relatively weak signals. 1.4.1. True Diversity The SWM7000 system comes with two dipole antennas (sometimes called "rubber duckies" or "rabbit ears") that mount on the back of the receiver. Two SWA700 Front-To-Rear cables are also included so that you can mount the dipole antennas on the receiver's rack ears. Dipole antennas have a polar pattern of sensitivity that forms a donut shape (toroid) with the antenna sticking through the donut hole. The receiver's reception is weakest along the axis of its antenna. The transmitter's antenna also has a donut-shaped polar pattern with the transmitter sticking through the hole. The transmitter's signal strength is weakest if you point the end of mic antenna directly at the receiver's antenna. If there was only one receiver antenna and you held the transmitter in a particular orientation, the signal strength would drop dramatically possibly causing dropouts. Another common problem occurs when a signal that propagates directly from the transmitter to the receiver is mixed with the same signal after it reflects off an object back to the antenna. Both signals are identical except the reflected signal is slightly out of phase. Mixing these signals can cause a dramatic drop in signal strength. This problem is common to all wireless microphone systems. 1.4.2. The SWM7000 receiver overcomes this problem by using a true diversity system that features two independent receiver circuits per RF channel. The receiver constantly monitors the signal strength from both antennas and automatically switches to the antenna with the strongest signal. 1.4.3. Antenna placement It is imperative that you orient the receiver antennas so that if one has a weak signal, the other will likely have a strong signal. Here is one way to do it. Orient the left antenna so that it points to 10:00 and the right antenna so that it points to 2:00. Placing the dipole antennas parallel to each other (for example, both sticking straight up) defeats diversity and causes dropouts. 1.4.4. Line of Sight RF signals will not go through metal objects and thick walls. Do not let the antennas be shielded by the equipment rack or the receiver's case. Both receiver antennas should be completely visible (in the line of sight) to the performer. There should be no obstructions. Use the SWA7000 front to rear extension cables (shipped with the receiver) if you wish to mount the antennas on the front of the receiver. Placing one or both antennas out of the line of sight of the transmitter defeats diversity and causes dropouts. 2 of 13 1.4.5. Range The SWM7000 with dipole antennas has a 300 foot range line-ofsight (no objects between the transmitter and receiver antenna, including hands and bodies). The range may be shorter if you stand between the transmitter and the receiver. 1.4.6. Grabbing the antenna of any hand-held or belt-pack transmitter will dramatically reduces the radiated power and increase the chance of a dropout. Keep hands off of the antennas. 1.4.7. Antenna Distribution Amp Receiver antennas in a rack can interfere with each other. Don't let them touch each other. If you have more than three adjacent receivers in the rack, it is recommended that you consolidate the antennas by using Sabine's SWA6SS Antenna Distribution Amp (ADA). The ADA will allow you connect up to six 2-channel receivers to a single pair of antennas. You can daisy-chain several SWA6SS ADAs together to connect up to 70 receiver channels to one pair of antennas. If you do not have an ADA, separate the receivers in the rack. Terminator caps are included in the distribution amp for unused connectors. You will probably have dropouts if you do not have terminator caps, especially if the plastic sleeves on the antenna connectors are black. Terminators are not as critical if the plastic sleeve on the insulation antenna connectors is white, but they are still recommended. (Antennas cannot be substituted for caps.) 1.4.8. Extension Antennas Use SWASS-EXT extension antennas if the rack is out of the line of sight or if the range is more than 100 feet, or so. 1.4.9. High-Gain Extension Antennas Sabine is now producing an optional high-gain version of the SWASS-EXT that increase gain from about 15 dB to about 25dB. We recommend these whenever your antenna cable is greater than 25 meters. They work well with shorter runs as well. There is no part number for these at the moment, but we will modify the standard antenna for high gain if you ask. 1.4.10. Placing Extension Antennas Extension antennas are sold in pairs. Remove the plastic cover. Notice that LEFT or RIGHT is printed on the circuit board. Position the one marked LEFT at stage left (on the left hand side of a performer facing the audience) and visa versa. When you mount the extension antennas on a stand or on a wall, make sure the pointed end of the triangle is down. (Stage Left and Stage Right are written on the backs of new extension antennas.) 1.4.11. In order for the system to be effective, both extension antennas should be in a good pickup position at all times but separated by about ten or fifteen feet if the antennas are within 100 or so feet. Separate them about 20 to 25 feet in very large rooms or fields. 3 of 13 If you put the antennas too far apart, i.e., at opposite ends of the room, or in separate rooms, to improve coverage, diversity is defeated and you will get dropouts. In other words, diversity is more important that coverage. 1.4.12. If you mount the extension antennas in the ceiling, the antennas metallic backplane must be orientated parallel to the floor and the antennas must not be blocked by pillars, lights or similar obstructions. Aim the hole in the plastic cover toward the podium. 1.4.13. Extension Antenna Cables Use coax cable to connect the extension antennas to the receiver or to the ADA. If the cable is about 40 feet or less, use Belden RG58 or equivalent cable. Use Belden RG8, or equivalent, for longer cables. Use the SWATNC-N step-down cable to connect thick RG8 cables with the extension antenna. 1.4.14. The SWASS-EXT extension antennas add between 10 and 18dB signal strength to overcome cable loss. Bad terminator connections are a common cause of dropouts. Check them carefully! 1.4.15. It is recommended that you use the dipole antennas for short distances rather than the extension antennas if the distance from transmitter to receivers is under about 75 to 100 feet. The dipole antennas are less likely to pick up interference generated adjacent to the performance area. 1.4.16. The left and right antenna cables should be the same length. Different lengths could defeat diversity and cause dropouts. 1.4.17. The extension antennas pick up pattern is limited to the front side with the plastic cover. There is very little sensitivity on the metallic backside. 1.4.18. Antenna Splitter A number of articles have been published warning against stringing antennas in series in an attempt to extend the operating range of a wireless microphone system. They warn about dropouts resulting from comb-filter interference. What these articles forget is that microphone systems have diversity. The chance of both sets of antennas will experience a filter at the same location and time is extremely low, especially if the antennas are offset as per the following diagram: 4 of 13 1.4.19. We have successfully solved dropout problems using this technique in a very large hall using 77 meter cable runs. Please note that high-gain extension antennas are required to overcome the loss of the splitter and please note that you must preserve diversity. The splitter we recommend can be found here: http://www.hyperlinktech.com/web/signal_splitters_2400_2way.php 1.4.20. You can also daisy-chain two antennas on one cable length by moving the splitter from the ADA to the first antenna. 1.4.21. Testing Your Antenna System. It only takes a few minutes to test your extension antennas, antenna cabling, and antenna distribution amp. Eliminate them from the system by simply placing a receiver on the stage with the dipole antennas. Check your RF performance (Use powered speakers patched directly to the receiver if you cannot connect to your sound system. If your dropouts go away, you know the problem is with the antenna system. 2. RF Interference. 2.1. Outside sources of RF in the 2.4 GHz band can interfere with your wireless microphone system if the outside source is strong compared to the transmitter's signal. Interference almost never causes dropouts, but it can cause ticking and sputtering sounds in the audio. Possible sources of 2.4 GHz interference include wireless LANs, some cordless phone, microwave ovens, cordless 5 of 13 security systems, wireless system control panels such as, Crestron, AMX, etc. 2.2. 2.4 GHz transmitters signal strengths are limited by governmental regulations. If the source of the interference is 50 feet or so farther from the antenna than the microphone, you will rarely hear interference. Most sources of interference in the 2.4 GHz band will cause interference only on about seven adjacent channels. You will still have plenty of clear channels even if there is a wireless LAN sitting on the receiver. 2.3. The best way to locate clear channels and avoid outside interference is to turn off the Sabine mics and then run the scan function in Sabine Remote. Turn on all known possible sources of RF interference in your area. Is there a microwave oven nearby? If so, put a cup of water in it and run it while you scan. The scanner lets you block out channels that have interference. 2.4. The next best way to locate clear channels If you cannot run a scan but you hear interference, move change to a different RF channels. Move at least ten channels up or down to avoid a single spread-spectrum source. 2.5. Generally it is best to clump the system's channels close together at the low or high end of the spectrum, i.e. channels 1, 2,3,4,5 or channels 65, 66, 67, 68. If there is another 2.4 GHz source in the room, clumping the channels reduces the chances of an overlap. 2.6. Many hotels, i.e., Hilton & Hampton Inn are now providing WLAN throughout their facilities so that customers can log on to the internet from anywhere in the hotel. These LANs, at least in the US, are restricted above our channel 10 and below our channel 53. This is just one more reason that our customers should clump the channels together at channels 70, 69, 68... on down to 54 and from Channels 1, 2,.3, up to 9. 2.7. Some Crestron system controllers with RF interfaces are set at the factory to spread signal throughout the entire 2.4GHz band. Not only will this interfere with the SWM7000, it will interfere with your LAN, Bluetooth, etc devices. Crestron gives instructions explaining how the reconfigure their controller so that it only uses 1/7 of the spectrum (www.crestron.com). This leaves plenty of room for your SWM7000 system and Crestron to work together without interference. Many other spread-spectrum devices also allow you to reconfigure their transmission b ...