Technical information

Instruments
dB RL 2 6 10 14 18 22 26 30 34 38 46
VSWR 8.7 3.0 1.9 1.5 1.3 1.2 1.1 1.07 1.04 1.03 1.01
RETURN LOSS = VSWR TABLE
MEASURING DIGITAL TELEVISION SIGNALS
Buying an instrument for Digital has to be more than a hit or miss affair. Yet, based on some of the information available, it can be little more than a
lucky dip.
What is it you want to measure?
Digital Channel Power, Bit Error Ratio, Modulation Error Ratio or Reflections?
Judging Digital TV Signal Quality by viewing pictures can deceive. With perfect pictures, total loss of service can be close at hand! Forward Error
Correction works continuously in digital transmission systems to keep received picture quality perfect. FEC makes field Signal Quality measurements
not just possible, but more important than signal level measurements!
Bit Error Ratios are perhaps the most useful quality measures of a Digital data stream, complicated by the need for 3 additional measurements
before a full Signal Quality position is clearly understood (MER, RU & CSI). The narrow measurement range between high and low signal qualities
makes it a demanding measurement of Installer Field Signal Meters. Digital Channel Power is the measure of digital signal level with no indication
of Signal Quality. DCP is difficult to measure properly on an Analogue Signal Meter.
Reflections actually help Digital TV, but there are limits to what receivers can handle. By seeing the reflections on an Adaptive Equalizer Response
(AER) display, the antenna can be positioned to ensure reflections are not likely to degrade reception. Unaohm’s AER function is helpful in
obtaining the most stable Digital signal and is particularly helpful with Single Frequency Networks. AER displays echo values across time and
distance, showing strength and when signals are outside the Guard Band and most likely to contribute to picture instability.
Laceys.tv sells and supports a very broad range of TV Signal meters from some of the worlds best known manufacturers. Talk to us about your
Digital TV measurement needs.
@20°C ±1.8%/10°C
MHz 55 211 350 550 870 1000 1750
RG59 6.18 11.79 15.22 19.36 24.75 26.54 35.81
RG6 4.94 9.43 12.2 15.62 19.99 21.46 28.66
RG11 3.12 5.95 7.74 9.88 12.8 13.88 19.51
TYPICAL COAXIAL CABLE LOSSES DB PER 100M
Antenna delivers:
35dBμV Poor picture, must be masthead amplified.
45dBμV Can be 100% with low noise masthead amplified.
55dBμV Not quite enough for 1 set, distribution amplified.
OK.
65dBμV O.K. for 2-4 sets if splitter and cable quality good.
Arriving at the set:
55dBμV Recommended minimum, allows for rain fade.
65dBμV Recommended for best picture quality.
75dBμV Recommended maximum signal level.
85dBμV Too much signal, tuner overload possible.
SUGGESTED ANALOGUE VISION SIGNAL LEVELS
TRANSMITTED VISION TO SOUND RATIOS
1st sound (L and R) -13dB from vision , 2nd (2xR) -20dB.
AUSTRALIAN TELEVISION RE-STACK CHANNEL BLOCKS
174MHz Block A 230MHz
Channels:
67899A101112
526MHz Block B 568MHz
Channels: 28 29 30 31 32 33
568MHz Block C 610MHz
Channels: 34 35 36 37 38 39
610MHz Block D 652MHz
Channels: 40 41 42 43 44 45
652MHz Block E 694MHz
Channels: 46 47 48 49 50 51
It is proposed that digital TV broacast channels will be re-arranged in the channel groups above, shortly after switchover is completed.
As the national plan is complex and some details are yet to be finalized, the latest details of the plans can be found at http://www.acma.
gov.au/WEB/STANDARD.PC/pc=PC_312417.
Narrow bandwidth antennas for each block are identified by the colours above, and show on page 9, 12, 13, 15, 16 and 17.
Catalogue 106
103