Frequently Asked Questions - All FAQs

FAQs - All FAQs

The gain and performance of the two antennas are the same.The ALP 600 is a PC board version of the ALP 700 and uses the same design parameters and the same number of elements. The ALP 600 uses a 4 layer PC board with strip-line matching and balun sections. We eliminated the external coax matching section that you will see on competing \"shark fins\" since we feel the coax solder joint can be broken if the antenna is really mistreated. The ALP 700 conventional antenna is not as rugged as the shark fin. We have, however, modified the ALP 700 to improve the ruggedness, by using a tapered nut for the jam nut on the antenna elements. The old elements would break at the first thread by the nut if the element was bent over. The new nut covers the threads completely and you can bend the element severely and then straighten it without breaking the element. The ALP 600 shark fin is still much more rugged, though. Aside from price, the only time not to use the shark fin, is if you are working in high winds or have the antenna mounted on a moving car or van.

The shark fin looks like a miniature sail. The shark fin is more expensive because the 1/8" thick, four layer board costs us more than all the metal and machining that goes into the ALP 700. I still find it hard to believe

The SPNConference has a powerful new echo canceller that can handle echo cancellation for multiple incoming signals from the far side. You can have multiple codecs and a phone line coming in and bridge all of them together. You will need to assign a minimum of four signal buses (or mixes) for conferencing. We suggest the following protocol. Setting up the AEC signal routing. Conferencing requires a minimum of four mixes. Two are dedicated to the AEC itself. These are called the AEC Reference mix and the AEC Signal mix. You will need to assign two mix buses in the ASPEN units for these two mixes. We recommend you use mix bus 48 for the AEC Reference and Mix bus 47 for the AEC Signal. The third is the SEND Mix (AEC Out) – you will need to assign a bus for each outbound signal. For example – if you have just a telephone line, you will need one SEND mix for the Tel. If you have one phone and two Codecs, then you will need three Send mixes, one for the telephone and one for each of the codecs. We recommend you use the mix buses 46, 45, 44 etc for these signal mixes.

This will keep all your conferencing mixes close together and separate from your local amplification mixes. Finally, you will need your LOCAL mixes – these are the signals which will be sent to your local amplifiers and may be shared with microphones. How many of these you need is dependent on the number of amplifier channels you have in use. Reference Mix – should carry ONLY the incoming signals from the far side. That would be signals from the telephone, and codecs – the inbound part of any two way communications line. DO NOT put any microphones or local line level sources (such as multimedia inputs) on this mix. AEC Signal mix – should have ONLY the local microphones. No multi-media sources, no line level inputs – microphones only. AEC Out Mix(es) – Will SEND the output of the AEC (which is the echo cancelled microphones), plus any multi-media sources to the fars side. If you want to have a bridged conference system, you will have the codec incoming going to the telephone SEND mix and the telephone going to the codec SEND mix. BE CAREFUL HERE! Make certain that you do not accidentally route the incoming telephone signal BACK on the outgoing telephone SEND mix! Or Codec to codec, etc! Local Mixes – this brings the audio from the far sides and the microphones into the room – note that we are routing the incoming phone and codec signals to the same buses as the local microphones which then feed to the amplifiers.

Currently, there is not a LecNet 2 version of the TH3A. You can, however, interface the TH3A with the DM series but you must reserve one audio input and one audio output on the DM. Use the AUX IN and AUX OUT ports on the TH3A tied to an audio output and audio input respectively on the DM mixer.
The TH4 (LecNet 2) is in development and will interface with the DM series mixers via the Digital interface. It will not require an audio input or output from the DM mixers to connect.

Active antennas sound good to customers but they have many shortcomings:  

  1. If the antenna cable is less than 25', an antenna amplifier is not necessary and is actually detrimental to the operation of system.  
  2. The antenna amplifier must be relatively wide band since it must handle all the frequencies to which the receiver may tune. If the amplifier is wide band, it will pick up many interfering frequencies.  
  3. It is difficult to design a high powered amplifier that is also low noise. The high powered amplifier is necessary to handle all the garbage that can come into a wide band amplifier.

To put it into a few words, antenna amplifiers are never as good as the front end of a well designed receiver. They are a necessary evil and should only be used when necessary. They are necessary under the following conditions:  

  1. When the antenna has to be more than 35' feet away from the receiver and the signal to the antenna is also weak such as antenna to performer distances of 100' or more. (If the signal to the antenna is strong then you will have enough signal to compensate for the cable losses.) Keep in mind that the antenna amplifier is NOT solving the weak signal to the antenna problem but just compensating for the cable losses after the amplifier. Again, the amplifier can't compensate for losses before the signal gets to the amplifier; only losses after the amplifier.  
  2. If there is a passive splitter after the antenna that introduces loss. This is equivalent to cable loss and the same rule applies; put the amplifier ahead of the splitter. A 2 way splitter has 3 dB of loss, a 4 way has 6 dB of loss and so forth.  
  3. When the receiver is a poor design with a noisy front end and the antenna amplifier can boost the signal enough to overcome the receiver self noise.  

Our "active" antenna setup consists of a passive antenna plus an external amplifier, the UHF50. That way you can use the amplifier only when necessary. We use a high power amplifier that is pretty quiet and we also put in a pre-filter that is two blocks wide (50 MHz) in front of the amplifier. It isn't as good a filter as those in our receivers, but it is better than the universal wide open designs. In addition, we make the gain of the amplifier adjustable so that you can match the gain to the losses in the cable or splitter system.  

What is confusing about the whole antenna amplifier issue is that cable loss degrades the sensitivity of the receiver but more gain doesn't improve it. In fact the additional gain leads to overload and intermodulation problems. This is Mother Nature saying not only can you not win, it's hard to break even. Another way to think about it is that our receivers are already about as sensitive as can be. If an additional amplifier could improve sensitivity, then we would have built it in. 

ASPEN latency is 1.33ms for the SPN812 and 1.43ms for the SPN1624. As you stack additional units, you add only 125 microseconds per additional link (two RU units have 250 microseconds). The 1GB backbone upon which ASPEN Net runs keeps latency extremely low. 125 microseconds is equal to a mere 6 audio samples.

Yes, the protocol for controlling the Venue wireless is easy to use and we are developing modules you can include in your programming. You can adjust levels, change frequencies, change operating modes (such as type of diversity), check transmitter battery levels and many other functions. You are not limited to just these two control systems. Because we have transport neutral protocol, there are many ways (including HTML pages) to control LecNet 2 devices.

Contact our control systems specialist, Frank Gonzales for assistance.

You can tilt the antennas so that they are at 90 degree angles to one another. That is to say, bend one 45 degrees to the left and the other 45 degrees to the right. The tilted antennas are a reasonable way to operate and the best way if the antennas are fairly close together since they couple together much less than if they are both pointed in the same direction (parallel).

The antenna diversity used in our receivers does not select one antenna or the other; it sums the two antennas together and corrects the phase of one antenna so that the antenna signals do not cancel each other out as they might do if they were 180 degrees out of phase. So it does not make too much difference which way the antennas point since the receiver will correct the phase.

Additionally, in any usual environment, the signals coming to the receiver from the transmitter are not in any well defined phase relationship or direction. The signals are reflected from cars, the ground, metal studs, wire in walls, camera equipment and even people, so that the signal that gets to the receiver is pretty well scrambled and impossible to predict. The problem with reception occurs when all the signals from all the reflectors get to the antenna and cancel out. If you use two antennas, then the signals probably will not cancel out at both antennas simultaneously. There is a new problem, though, if you simply add the two signals together. When the signals at each antenna are equal and exactly out of phase they cancel out at the receiver. The phase diversity system that we use on our small receivers detects this condition and simply inverts the phase of one of the antennas. Now the antennas add the signals together for a 3 dB pickup in power. For a good explanation of this, that is more comprehensive than what I can do here, go to this link to our web site.

Dropouts and Noise-ups 1

It is part of our wireless guide. In fact you might want to down load the entire wireless guide because it is pretty good and pretty neutral in its treatment of wireless microphones.

ASPEN is self organizing. You won't do anything. Once your rack is built and the units interconnected with the single Cat6E cable, the ASPEN units will organize themselves into the correct Master/Slave configuration automatically. The top unit will become the master and all the subsequent units will be slaves. If you add another unit to the stack, it will be added automatically in about 90 seconds. Because the 48 mix buses are bidirectional, whatever assignment you have made for the output mixes will remain correct regardless of position n the rack.

The only effect the sequence will have in your rack will be on the control side. You can control an entire multi-unit ASPEN system through a single RS232 port but it MUST be the RS232 on the Master unit. Commands to the slaves will be preceded with a numerical designator surrounded by square brackets so the stack of ASPEN units will know which command is for which unit. Example : [2]run(3) will run macro number 3 in the second unit in the rack. So, the position of the unit will be important when writing control code.

The AM series (also called LecNet) used a communications protocol developed before the dominance of third party control systems. Primarily intended for our software to control AM16/12, AM8, DSP4/4 etc, it was a hexidecimal programming code designed for use by computer programmers. The PT3 is a protocol translator that can easily convert AMX commands into a string of LecNet commands. Up to 92 AMX commands, (pulse, level, or channel) can be associated wih a LecNet command or string. The PT3 is not required, it is simply a programming aid designed to make AMX code writing easier. You CAN control with AMX directly but the code will be more complex. The PT3 cannot help with Crestron systems. The PT3 is NOT needed for the DM LecNet 2 series products.

It is surprisingly hard to do. The big problem is the battery terminal voltage is heavily influenced by how the battery has been discharged in the past. If it has been run down slowly with power gradually pulled out say over a 24 hour period, the relationship between remaining battery capacity and terminal voltage is fairly well defined. If the battery has been discharged heavily, say by a Lectro UM250, the relationship is not so clear. Basically the battery bounces back to a high voltage and can look like it is still pretty fresh. Under either a light or heavy load it will run down quite rapidly. The problem is, the battery tester has no way of knowing the past history of that particular battery. 

As a demonstration, if a fresh 9 Volt is accidentally shorted out with a piece of metal for 1 minute, you will get very odd results. The battery will get moderately warm. If the battery then sits unused for 8 hours, the terminal voltage will then measure pretty close to a new battery even under a brief load, but it will only run a transmitter for 5 minutes or so and then die almost instantly. In fact, if you then let it sit for a while again, the voltage will come back up again and die again in a transmitter in just a few minutes. I agree that this is an extreme case but it does demonstrate the problem of prior history.

Even when you know the history you can get bit. Recently we have been running battery tests on different brand batteries and we have found that some alkaline batteries tend to die very rapidly at the end of their life but other brands continue to run with lots of warning before they finally die. What's worse, different batteries from the same manufacturer may act differently. The reason we did the test is that we were getting complaints that the UCR201 was not giving sufficient warning with batteries made by XXXX brand, a major manufacturer. We tested the batteries and found that Evereadys gave 34 minutes of operation after the battery indicator started flashing its warning and the XXXX brand were giving about 3 (!) minutes of warning. We found this to be consistent with XXXX from 3 different parts of the country. Since so many of our dealers sell XXXX, we aren't sure what to do other than recommend Eveready as the standard. The XXXX brand is a perfectly good battery but it has a slightly different chemistry that is optimised for things other than high current drain. 

The safest answer is that a low voltage reading will always indicate that a battery is weak but a normal or high reading may not necessarily mean that a battery is good. This is why so many pros that absolutely depend on their equipment, put in a fresh battery at the beginning of a job or whenever there is the slightest doubt that the battery will "last long enough"