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FAQsAmplifiers
What is the P1dBm compression point & why does it matter?Every wlan amplifier has a compression point and gain. The TX gain on a wlan amplifier is a measure of the amount of amplification in (dB). This gain holds true for RF input power up to a certain point. By increasing the input power more and more the wifi amplifier starts to compress and eventually the wlan amplifier actually start to lose gain. When the input RF power is high enough to cause the TX gain to drop by 1dB, this is the point called the P1dBm compression point. This is also where the wifi amplifier is rated for maximum usable power. When selecting an wlan amplifier one should always consider the P1dBm compression point of the amplifier; it?s a measure of how much horse power is under the hood. Compressing the wifi amplifier beyond the P1dBm point can potentially decrease the operational life and damage the device and possibly void your warranty. In addition overdriving and compressing a wlan amplifier beyond it?s P1dBm point will cause unwanted distortion products and harmful interference to both in-band and out-of-band signals. When using fixed gain wifi amplifiers one needs to pay close attention to not exceeding the P1dBm point. AGC style amplifiers automatically adjust their gain to maintain linearity and thus retain a fixed Power Output at the antenna port. When you say the unit has an average power limit and a peak power limit when using OFDM what does that mean?OFDM (Orthogonal Frequency Division Multiplexing) is the type of modulation used in 802.11g and 802.11a devices. OFDM modulation with its multiple carriers requires a vary wide power range to perform properly. This wide power range is for the AM bursts and often described as headroom and measured as Peak Envelope Power (PEP). If you do not allow enough headroom before the amplifiers P1dB compression point you will overdrive the wifi amplifier and cause distortion products that compress the modulation and reduce data throughput. In addition overdriving the amplifier beyond it?s P1dBm point stresses the amplifier. When using this device with an OFDM signal we recommend a 4-6dB back off from the P1dBm point. This will provide the additional headroom for the OFDM modulation and yield maximum data throughput. Thus, using a 1W amplifier with an OFDM signal the amplifiers average power will be +24dBm yet the Peak Envelope Power (PEP) will be +30dBm. Basically using a fixed gain wifi amplifier the (sum of Radio Power in (dBm) + Amp TX gain in (dB) cannot exceed +24dBm using OFDM). Our OFDM AGC amplifiers are advertised at their average power unless otherwise notes so we handle this peak to average difference in the background. Does it matter what radio power I use with a fixed gain amplifier?The radio power, as well as the cable loss between the radio and the wifi amplifier, is critical when using a fixed gain wlan amplifier. You must be aware of and consider the RF radio power, pigtail losses and wifi amplifier TX Gain before selecting a fixed gain wlan amplifier. If you provide the fixed gain amplifier with too much power you will overdrive it potentially damaging the unit and creating system performance issues. Too little power and you will not obtain the intended results. Our AGC amplifiers handle this in the background by reading the radio input power and adjusting the amount of TX gain applied to ensure that the rated output is reached. What does fixed gain mean?Fixed Gain relates to the amount of amplification provided for both the transmit (TX) and receive (RX) signals when using a bi-directional wifi amplifier. Fixed gain wlan amplifiers are very straight forward devices; they simply add a specified amount of amplification or gain to your signal. This holds true up to the compression point of the wifi amplifier, then the gain actually decreases with more-and-more input power. We?ll cover more on compression later. When calculating how much gain I need, and what output power will I have? One must first convert losses or gains to (dB) and Power to (dBm). Do not try to add Watts, first convert Watts to (dBm) then add in gains in (dB). The units of (dB) are relative and the units of (dBm) represent power. Thus, if I have a input power from my radio of (32mW) and I have a wifi amplifier gain of +14dB, I can calculate the output power by first converting my radios Watts to dBm. Thus 32mW is 15dBm. One can find this conversion of Watts to dB in our Calculations Section. Then it?s just a simple addition (Power radio (dBm) + Gain amp (dB) = Pout (dBm)) or (15dBm + 14dB = +29dBm). +29dBm is (800mW) and this is the power which will be at the antenna port. Now let?s cover compression point of the wlan amplifier. Every wifi amplifier has a compression point and gain. The TX gain on a wifi amplifier is a measure of the amount of amplification it?s units are in (dB). This gain holds true for RF input power up to a certain point. By increasing the input power more and more the wlan amplifier starts to compress and eventually the wifi amplifier actually start to lose gain. When the input RF power is high enough to cause the TX gain to drop by 1dB, this is the point called the P1dBm compression point. This is also where the wlan amplifier is rated for maximum usable power. Once you know what the P1dBm compression point of the wifi amplifier, is you can work backwards and calculate how much gain do I need in the amplifier to reach but not exceed this P1dBm point. We offer factory default settings for indoor and outdoor use that are geared to work with most systems and applications using radios with +15dBm output power. In addition we offer custom user specified gains choices. By offering this we make custom wlan amplifier gains available at a standard price. Fixed gain units are generally less expensive than AGC units making them the economy choice. The fixed gain wifi amplifier makes perfect sense if you will be installing it in a position that is unlikely to change especially if you will be doing multiple installations using the same setup. This makes the fixed gain unit a drop in device since you only have to calculate your system power levels once. For a more plug-and-play type approach one might consider an automatic gain control (AGC) wlan amplifier before making your final choice. What does Automatic Gain Control (AGC) really do and why should I use it?Automatic Gain Control or AGC as it is commonly called offers a plug-and-play type functionality. The AGC feature of the wifi amplifier will adjust the gain up or down so that it always maintains a steady output power equal to it's rating regardless of changes in the input power or cable loss between the radio device and the wlan amplifier. Unlike our competitors, we test the final power of the wifi amplifier at the antenna port to ensure that your output power is as rated. Please note for the AGC to function properly you must have at least +2dBm of signal at the amplifier to switch from receive to transmit mode and you cannot feed more than 200mW or +23dBm of signal into the unit from the radio device side. Example: If you use a standard 32mW radio device you have +15dBm of Radio signal strength. If you have 7dB of cable loss (equal to 100' of LMR 400) between the tower bottom mounted radio and the tower top mounted +30dBm (1W) Antennafier? WiFi Amplifier you would be providing the wlan amplifier with about 8dBm of signal. This is more than is required to switch the wifi amplifier to TX mode. The wlan amplifier will sense the signal strength of +8dBm and then add +22dBm to it to bring the signal power output to +30dBm or 1W as rated at the antenna port of the amplifier. You should use an AGC wifi amplifier when you want the ease of designing your system power level or Effective Isotropic Radiated Power (EIRP) based upon the constant AGC controlled output. You may also find that having AGC WLAN Amplifiers offers a nice standardization where you can mix and match radios and cable types / losses and still use the same wifi amplifier from installation to installation. This allows you to keep a spare unit that will work as a drop in replacement for all or many of your systems depending on the antenna used and the EIRP expected. Can you modify the unit to use less DC power?Yes we have some modifications that we can do to reduce the power consumption. This entails removing items and rerouting some processes that generally cut power on the TX or RX sides depending on the modification. This is something you should call and discuss with us. We are always happy to perform custom and semi-custom work for our customers. How do I use this POE Amplifier?This POE wifi amplifier is a combination of our high performance DC-DC Converter and our Antennafier? WLAN Amplifier on one platform. Our POE KIT is powerful enough to operate your amp and radio with a single CAT-5 cable. Many competitor solutions require separate POE sources for the radio & amp. Installation is easy and involves simply removing the POE power inserter provided with your POE wireless radio and replacing it with our POE power supply and power inserter unit. We offer several POE power supplies in various voltages to match the current POE radio requirements. This POE supply will provide enough energy to power a wifi POE amplifier and POE radio. Refer to the installation diagram on the datasheet. Should I mount the amplifier at the tower top or tower bottom with the radio?This is an often asked question and there are several correct answers. In the cellular telephone industry all of the equipment is mounted at the base to provide ease of access to active components like amplifiers and radios. However it requires very expensive low loss RF cable to preserve RF performance. In most WiFi applications the cost of developing a base mounted system is cost prohibitive and the split system where the radio is at the base and a wifi amplifier is at the tower top with the antenna is the favored approach. A split system uses our Outdoor WLAN Amplifier model that includes a DC Injector that is mounted near the radio at the base that provides DC power on the coax cable that supplies power to the wifi amplifier mounted close to the antenna. The benefit of this system is that it allows one to use a cost effective indoor commercial radio and yield the high performance of an outdoor solution. In this case the weatherproof wlan amplifier sets the critical RF performance at the antenna (Low Noise Figure in RX and boosted TX power). Our Outdoor POE amplifiers shoudl also be mounted close to the antenna. The POE radio does not need to be installed next to the POE amp. It?s at the antenna where you want to preserve these important system parameters. In this split system approach the RF losses associated with the tower coax are not setting the critical system performance. The ?cellular? approach limits all outdoor components to passive elements (non powered devices). This is what cellular companies do, yet it requires very expensive low loss coax to be used from the amplifier to the antenna. Every dB of loss associated with this cable is directly added to your critical RX Noise Figure and robbing your TX power. We recommend no more than 3dB of loss in these applications, since 3dB is ? your power and equates to about 25% reduction in your overall system range. How is the 2400 LT/DT Series Field Tunable and how does this help me?The 2400 LT and DT Series Tunable Antennafier? can be adjusted in the field using the include Tunable Controller? connected via USB to a PC with our software installed (Indoor units have the controller function built in). The 2400 LTX-POE and DTX-POE Series Tunable Antennafier? can be tuned in the field using the optional Tunable Controller? installed between the POE Radio and POE Amp. Once connected and power is supplied to the LT/DT Series Amplifier you can change the TX and RX Gain settings. For DT Series units the channel filter can also be adjusted at this time. The easy to use GUI makes gain and channel settings a snap as well as providing an RF input level from the radio and a status report from the amp for troublshooting purposes. The LT/DT Series Antennafier? will remember its last programmed settings even after power cycling. This allows the unit to be used in the field without the Tunable Controller? attached. The software necessary to interface with the Tunable Amplifier is provided with any LT / DT Series Tunable Antennafier? or Tunable Controller? purchase. You can also download them for free using the links above. The field tunable features offer incredible versatility never before seen in a device of it's kind. This option gives you the control over circumstances that can change in the field. Rather than having fixed devices that you must physically change out when your RF environment is negatively impacted you can simply change settings at your leisure with no additional expense or costly and dangerous tower climbing. This is crucial in the winter when tower climbing is difficult or impossible. You can adjust your TX gain in the field to give you maximum power with a variety of antennas (EIRP regulations apply) and cable loss conditions. You can adjust your RX gain to provide the perfect amount of receive amplification without raising the noise floor unnecessarily. You get the benefit of -50dB adjacent channel rejection from High Q filtering while maintaining the ability to select and change your filtered channel (DT Series units only) in the field from the ground. This means that if a competitor or a change in your infrastructure require(s) you to change the channel on this system you could do so without climbing the tower or switching out a fixed tune channel filter. Please note that the 2.4GHz WiFi channels have some built in overlap which no channel filter can eliminate. Proper channel planning is necessary to alleviate this concern. What channel should I use and how does the channel filter help me?As I am sure you are already aware the WiFi bands are getting more and more crowded and will get worse before they get better. Channel filtering is the next logical step beyond channel selection. Logical channel selection will help you deal with normal co-location issues and general network layout. Remember competitors will want to use the "good" channels too. When you have co-location or interference issues that cannot be solved by channel selection you must combine filtering with good channel selection or pay for equipment to change bands. Filtering gives you a specific amount of rejection to the interference. It does not make the interference invisible to your receiver. By adding a high amount of rejection your receiver is able to now distinguish the intended signal from the noise and interference. Please note that you cannot filter out in band interference or interference that is already in your channel. If you are on Channel 6 and are getting interference from a competitor also on Channel 6 you only option is to change channels or convince your competitor to do so. Working with your other local WISPs when selecting channels and filters will benefit them as well as you. The channels can be logically divided and protected with filters so that channel re-use can occur and everyone can share the limited channels and prosper. The diagram below provides a graphical rendition of the 802.11b/g channels and is provided to help you picture how specific channels will react to other channels in terms of potential interference and co-location problems.
Advertised 802.11g / 802.11a output power and how do I compare from one manufacturer to another?By definition the IEEE 802.11g / 802.11a standard uses OFDM signal modulation. This type of modulation called OFDM requires addition headroom or Peak Envelope Power (PEP) for field usable output power. Many other manufacturers are advertising only the peak power of their 802.11g / 802.11a amplifiers. This means that your field or usable output power could be as much as 4dB-8dB less than advertised. This reduction would make a competitor's +30dBm or 1W 802.11g / 802.11a amplifier drop to +24dBm or only 250mW of usable average power. We have designed our amplifiers to provide the advertised power using the 802.11g / 802.11a OFDM signal without compressing the amp so when you buy our 1W 802.11g / 802.11a amplifier you get +30dBm or 1W at the output or in other words everything you paid for. Antennas
How much base station antenna isolation is required?We would like to see at least 30dB of isolation between base station antennas. Antenna isolation increases with distance. Antennas spaced at 3 feet horizontal spacing will provide about -39.4dB loss (isolation) between them. This increases to about -41.9dB at 4 feet and -43.84dB at 5 feet. As with anything RF, there ar many factors which can affect system performance. A big one when dealing with antenna isolation is that coupling to tower structures can reduce effective path loss between antennas. This could change the necessary spacing for any given installation. To calculate isolation for directional antennas like sector antennas, you have to add the front to back/ sidelobe spec to the gain (dBi). For instance; with a 16.5dB sector and a front to back spec of -14Bi, you have effective gain toward the side or back of the antenna of 2.5dBi or .35dBd. You can use the effective gain to calculate the best horizontal or vertical separate to give you the desired isolation. You'll see that you get the best isolation if you can space the antennas with some vertical separation. Vertical separation is measure from antenna center to center in feet. Please see our calculations page for additional information. Converters
How does the Up/Down Converter work and what are the benefits?The 915 UDC offers a special solution for those installations where line of sight is challenged and 2.4GHz performance is deficient. The 900MHz signal performs much better than 2.4GHz with obstructed line of sight, like tree foliage, and provides much less cable loss which is a benefit in a variety of ways. To perform this task requires two 915MHz converters, one attached to each radio. First the Up↕Down Converter takes the standard WiFi 2.4GHz signal transmitted and converts it to the center of the ISM band (915MHz) in addition it provides signal amplification to boost the both TX and RX signal strength. The RF link between radios then accomplished via 900MHz antennas. This allows an area of potential customers that could not be reached from your existing 2.4GHz network to be added to your client base using a point to point link over to this new region. You can also create a 900MHz hotspot to service smaller neighborhoods. Since the converters uses a wide channel to maintain 802.11b/g throughput the number of clients tends to be limited to what a single radio device can handle unless directional antennas are used. The 900MHz converter was designed to breach line of sight problems path loss problems for outdoor WiFi networks as well as indoor WiFi networks where the commercial building construction limits traditional 2.4GHz WLAN performance. Filters
Can RF Linx meet my custom filter requirements?RF Linx specializes in providing "solutions" products for the wireless industry and can provide custom filter designs to augment our production offerings. We can provide Bandpass, Lowpass, Highpass, and Bandstop / Notch filters as well as Multiplexers. Custom filters may require additional design cost and manufacturing time. Why do I need a RF Linx Ultra High Q Filter?A RF Linx Ultra High Q Filter is used to reduce interference which improves the performance for co-located equipment and radio reception in general. Interference is caused by transmission sources near the channel you are using to transmit. These unwanted transmission can interfere or cover the intended signal. Please note that a filter cannot remove intraference, or interference on the same channel you are using. How do RF Linx Ultra High Q Filters work?The RF Linx Ultra High Q Filter will provide rejection or block interfering signals. The amount of rejection or blocking action is based upon the design of the filter. A higher performance filter will provide more rejection. The rejection or blocking action of the High Q Filter is applied against the interfering signal with the goal being to reduce the strength of the interfering signal below you intended signal. A filter will not make an interfering signal invisible to your reciever. It is important to know what and how much you are trying to filter out before selecting a filter for proper results. What is the difference in the number of poles in a RF Linx Ultra High Q Filter?Each pole is a filtering circuit. The more poles a filter has increases it's rejection or strength. Generally all RF Linx filters have 8 or more poles to provide the best performance against high level interference. Some competitors offer 4 pole filters but in our opinion they are not strong enough to provide the intended outcome. General
What are the NEMA and IP Ratings and what do they mean?NEMA Standards Publication 250-2003, ?Enclosures for Electrical Equipment (1000 Volts Maximum)? is the standard which is used to define various NEMA ratings on electrical enclosures. NEMA Rating Types Explained: NEMA 1 NEMA 2 NEMA 3 NEMA 3R NEMA 4 NEMA 4X NEMA 6 NEMA 7 NEMA 9 NEMA 12 NEMA 13
The IEC standard #60529 defines waterproofing ratings (IP Codes) for various levels of protection against water ingress. This standard is used to define everything from electrical connections to enclosures. IP (Ingress Progress) Codes in accordance with IEC 60529 There are several different uses of IP Codes, as described in IEC 60529. IP Codes can have the following arrangement: 1. First character only, such as IP 3X, The first character indicates the degree of protection against the ingress of solid foreign objects. First character definitions are as follows: 0 - Non-protected The second character of the IP Code indicates the degree of protection against the ingress of water without harmful effects. Second character definitions are as follows: 0 - Non-protected Orders
Do you offer additional discounts for large orders?Our pricing is geared toward the VAR and Professional Installer with standard products being sold through distribution. With this in mind please see our "Where to Buy" page to find the Distributor or Reseller closest to you. Please give us the opportunity to directly quote your custom amplfier project. |
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