UNDERSTANDING DIGITAL TV - Ro.Ve.R. Laboratories S.p.A.

More documents

Recommendations

Info

PROPAGATION EFFECTS ANTENNA DISTANCE TABLE CHART: DISTANCES BETWEEN ANTENNAS ANTIREFLECTION ANGLE FREQUENCY IN MHz DEGREES Distances in meters The values are critical, use the table only for the first approximation, then adjust the distance until you reach the maximum spectrum flatness 24
This chart is useful, even if it does not cover all frequencies and angles. The values are calculated exactly, but you must carry out an experimental set-up, because you will never exactly know which direction a signal is coming from. It is especially useful if you want to see if a mechanical system is physically possible, given that sometimes very large distances are involved. If the distances are too small and the antennas are touching, just double the distance to obtain an acceptable one. The system works very well, especially in the case of reflections from the terrestrial surface, with antennas fixed to a mast, one below the other. This is often found near lakes, or in the case of sea travel, but in these cases the angles are small. A good test is to vary the height of the receiving antenna. If this causes ripples in the spectrum, that vary with height, then you can be certain that there is a reflection from the ground. If the depth of the ripples is considerable, or part of the spectrum is missing, then you must be careful, especially if the reflection takes place on water, given the inherent variability of the situation, basically it changes often during the day and night. 25
Page 1 and 2: UNDERSTANDING DIGITAL TV • Radio
Page 3 and 4: SUMMARY 6 Radio frequency spectrum
Page 5 and 6: The difference between the two sign
Page 7 and 8: The function that allows you to fin
Page 9 and 10: The power of the digital signal is
Page 11 and 12: The modulation is the same type for
Page 13 and 14: We know that signals can be “poll
Page 15 and 16: The DVB-T signal has this behavious
Page 17 and 18: Here you can see a schematic block
Page 19 and 20: When it is said that a DVB-T system
Page 21 and 22: Let us assume that the electromagne
Page 23: We will illustrate a laborious, but
Page 27 and 28: Another situation where the antenna
Page 29 and 30: The back to front antenna ratio is
Page 31 and 32: The reflections caused by a mismatc
Page 33 and 34: Since the system is immune to refle
Page 35 and 36: Operation is based on being able to
Page 37 and 38: Nearly every instrument has an SFN
Page 39 and 40: Here are a number of rules to impro
Page 41 and 42: This picture shows an example of an
Page 43 and 44: As an example, we have superimposed
Page 45 and 46: The diagram clearly shows the trans
Page 47 and 48: To obtain minimum reception stabili
Page 49 and 50: These predictions are verified when
Page 51 and 52: The electromagnetic field is measur
Page 53 and 54: Even if the MER is a good indicator
Page 55 and 56: The diagram shows once again the th
Page 57 and 58: This table is calculated for system
Page 59 and 60: Micro-interruptions are not always
Page 61 and 62: So ripple (waves) in the spectrum p
Page 63 and 64: In Figure 3 and 4 you can see the s
Page 65 and 66: Figure 5 shows DVB-T signal ch.8 th
Page 67 and 68: Using this case study you can see h
Page 69 and 70: Directive 2004/108/EC requires that
Page 71 and 72: The diagram shows the real case of
Page 73 and 74: MPEG4 REAL TIME SPECTRUM 6-HOUR BA
Page 75 and 76:
mod. HD COMPACT STC THE MOST ADVANC
show all

UNDERSTANDING DIGITAL TV - Ro.Ve.R. Laboratories S.p.A.

Create successful ePaper yourself

Delete template?

Save as template?