Step 4 Checking Third-Order Intermodulation Distortion - Sony DWM02/14 Product Information

Configuring a DWX System

Step 4 Checking Third-order Intermodulation Distortion

Power up all transmitters for channels other than the desired channel, and generate third-order
intermodulation distortion (subsequently called interference) in the receiver for the desired channel. Assign
a range of parameters for TX output power and RX attenuator settings and check the interference noise level
with each setting.
Procedure
14 Power up all transmitters for channels other than the desired channel. Establish a setup
simulating the expected conditions during actual operation, and have a person with the TX
stand in a position closest to the antenna.
Example: If the TX is the DWM-01, it should be held in the hand, close to the mouth.
* Equipment other than TX (RX, boosters, etc.) should be constantly on.
15 Using the RF level meter of the RX set to the channel whose TX is switched off, check the third-
order intermodulation distortion noise level in the channel.
Setting example for checking
 Band to use: Band established in step 1.
 Group to use: Group established in step 1.
 Antenna installation location/orientation: As determined in step 2.
 Antenna gain: As determined in step 2.
 Number of antennas: As determined in step 2.
 TX RF power: Setting that cleared the requirements of step 3.
 RX attenuator: Setting that cleared the requirements of step 3.
Check procedure
Check the RF level meter indication.

For stable reception, sufficient RF power levels should be obtained in the desired channel, and at the
same time, the D/U ratio between desired channel and interference should be at least 20 dB. Decreasing
the system-wide RF level will decrease interference in the desired channel by a factor of 3. Consequently,
if the D/U ratio is insufficient, reducing the RF lower will provide an improvement. For example, when a 5
dB attenuation is introduced, the level in the desired channel will decrease by 5 dB, but the interference
level will decrease by 15 dB, thereby yielding an improvement in D/U ratio by 10 dB. The same applies to
the attenuation of RF power due to distance. If the RF level is too low, the available distance will decrease,
resulting in an insufficient service area. But if the RF level is very high, this also can cause problems because
the required D/U ratio cannot be obtained in the antenna vicinity. The resulting service area will be shaped
like a doughnut, with a large hole in the middle, which also is undesirable. Therefore, 50 mW output of the
TX is not suited for simultaneous multi-channel operation.
52
Making and Checking RF Settings (UHF)
If the TX is the DWT-B01, it should be worn on the hip, and the person should stand at the rim of the
stage, approaching the antenna.
In principle, the noise level should be less than
10 dBμ (RF level meter should be consistently out).
Note
TX RF power
Low
High
A
Low
Small
Service area for single channel
Zone A Zone B
Interference is low, Good balance between
but RF level in desired channel and
desired channel is interference RF level. Desired
also low, resulting in service area is achieved,
insufficient service also during simultaneous
area. multi-channel operation.
Sample results
RX ATT
High
Low
Third-order intermodulation
B
distortion noise level
C
High
Large
Zone C
RF level in desired channel is
high, but interference level is
also high. During simultaneous
multi-channel operation,
desired service area will not be
achieved in antenna vicinity.
Service area
TX RF power
1 mW 10 mW
Step 3 Step 4 Step 3 Step 4
Setting 1 Setting 4
10 dB
Poor (Good) Good Good
Setting 2 Setting 5
5 dB
Fair (Good) Good Good
Setting 3 Setting 6
0 dB
Good Good Good Fair