Pictures below show the difference in floor noise while LNB is powered off or powered on. When the power is ON, this LNB has the noise value of 56dBuV. When the power is OFF, the same LNB has about half the floor noise of below 30dBuV.
Floor Noise when LNB is ON Floor Noise when LNB is OFF
If the device does not receive analog signal while LNB is powered ON, then the Level Meter DS200 will measure the floor noise and displays it as analog level.
Floor noise differs according to the LNB. The lower the CN value of antenna is, the higher the floor noise would be. When this is the case, you need a larger antenna.
2. Typical Signals
When Level Meter DSA200 catches clear signals, it looks like the pictures below.
OFDM NHK 509MHz 19CH 74dBuV
＿＿BS Signal 1280MHz BS-13CH 74dBuV
110° CS 1653MHz ND4 50dBuV
＿＿UUnclear signals around 1128MHz 70dBuV
It often times catches very unclear signals; however, when analyed with spectrum analyzer, it shows a group of clear signals. Although they are digital signals, because of unclear data it is not locked, CN or BER values don't show, therefore misinterpreted as analog signals or malfunction of the Level Meter.
3. Measured value of Leader FL990 and DSA200
Above NLB foor noise are measured regardless of the angles of antennas, so users may questions the malfunction of the Level Meter; however, as long as signals exist, any level maters could catch such signals. Leader FL990 and DSA200 can measure floor noise as below. 53.7dBuV and 56.9dBuV both show the values very close to correct values.
DSA200 and LF990
4. Antenna and distributor used in this experiment.