Grounding Techniques; Samson Low Power Technique - Samson SYNTH SIX Manual Del Propietário

Grounding Techniques and the

Samson Low Power Technique

Grounding Techniques

The UR6D and DA6 both contain a switching power supply that will add an audible hum to your audio signal if the
unit is not plugged into a properly grounded three-pin AC socket. Under no circumstances should you use a
three-prong to two-prong adapter to lift the ground from the UR6D / DA6 AC cable.
If the unit is correctly connected to a grounded three pin socket and you still experience hum or buzz when using it
with other audio devices, there's a simple test to determine the source of the problem: with all devices powered on
and connected with audio cabling, remove each device, one by one, from the rack. If the hum disappears when a
particular device is removed, that device is probably the culprit. If the offending device uses a two-prong plug (or an
external two-prong adapter), try reversing the plug in the socket. If that doesn't work, try physically grounding the
UR6D or DA6 chassis by connecting a wire from the ground screw to earthed metal such as a water pipe.
In addition, you can minimize possible interference by planning your RF antenna, audio, electrical, and computer
cable runs so that they are as far apart from one another as possible and so they don't run parallel to one another.
If they have to cross, try to ensure that they do so at a 90° angle (that is, perpendicular to one another). In particular,
try to keep audio cabling away from external adapters
If you're using the UR6D and/or DA6 in a fixed installation, you may want to create a star ground network for all your
audio devices. This is by far the best technique for avoiding grounding problems. It involves using a formidable
ground source such as a cold water pipe or a copper spike driven into the earth. A thick cable is connected to that
source and is then brought to a central distribution point; from there, individual cables are connected to each piece of
equipment. This setup also requires that you lift the ground plug of all three-prong AC connectors, so there is the
possibility of danger if it is done incorrectly. We strongly recommend that you contract with a qualified professional
to carry out this or any kind of electrical work.
Samson Low Power Technique
Samson Technologies has developed a unique technique for multi-channel operation of the Synth Series 6 wireless
system in indoor, fixed site applications where the RF conditions are carefully controlled. This should only be under-
taken by a qualified RF engineer with the necessary test equipment and training.
Whenever two or more transmitters are used in neighboring frequencies there is a chance of interference. This is
because their two different frequencies produces a third frequency which is known as intermodulation distortion.
In order to reduce this interference, it is good practice to carefully select the frequencies of each channel (that is,
create a good "channel plan") so that the spurious emissions from one channel do not clash with another. The
problem is that as the number of simultaneous channels increases, it becomes more and more difficult to find a good
channel plan.
Logically, then, the best way to increase the number of available simultaneous channels is to reduce the spurious
emissions. This is precisely the function of the Samson Low Power Technique. It exploits the fact that, as carrier
power is reduced, the spurious emissions also are reduced. Best of all, this reduction is disproportional—even
reducing the carrier power slightly results in a dramatic decrease in spurious emissions. Once the spurious
emissions are reduced to insignificance, a channel plan can be easily selected—in fact, you can simply adjust the
transmitters in the system to be 250 kHz apart.
The Samson UT6 and UH6 UHF transmitters can be set to either 10 mW or 1 mW RF output power. To use this
technique, the output power must be adjusted down to 1 mW. Lowering the output power of the transmitter,
however, also reduces the active range of the system, however, as shown in the table below.
Output Power of Transmitter
In order to counter this (and to reduce the greater chance of interference from outside RF sources), the use of two or
four AN-81A or AN-82 powered antennas—strategically mounted in areas of maximum transmitted power and lowest
interference—is an absolute requirement. These antennas contain booster amplifiers that provide a relative gain of
+8 dB. The AN-81A / AN-82 attenuation switch should be set to the 0 dB position, as should the UR6D antenna
attenuation switch. See the AN-81A / AN82 owners manual for information about recommended cabling.
During operation, all transmitters must be powered on. If any are not being used, their "Audio" switch should be in
the "off" position or else both the unused transmitter and its associated receiver must be switched off. The use of the
DA6 antenna distribution amplifier (as described on pages 12 - 13 in this manual) is recommended. It is also
recommended that all receivers and distribution amplifiers be mounted together in the same rack in order so that
the shortest length RF cable possible can be used for receiver antenna interconnections.
Maximum Active Range
10 mW
1 mW
130 - 260 feet
60 - 130 feet
16