Technical FAQ

 

 

 

CCIR Television Transmission Characteristics

 

 

CCIR: Committee Consulatif Internatioonal Radiocommunications NTSC: National Television Systems Committee

 

PAL: Phase Alternation by Line                                                               SECAM: Sequential Color with Memory

 

OIRT: Organisation Internationale Radio diffusion - Télévision 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Optical Fiber Color Code

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Digital Transmission Standards

 

 

SONET:	Synchronous Optical Network         OC-* Optical Component -- Level
SDH:	Synchronous Digital Hiérarchie       STS-*   Synchronous Transport
ISDN:	Integrated Service                            Signal - Level
	Digital Network

 

 

 

 

Digital Signal Formats and

Occupied Bandwidth ¹

 

 

1 Occupied bandwidth at -3 dB points

 

2 Including overhead

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

System Calculation

 

Decibel

 

The decibel is a logarithmic ratio between two power levels:

 

  dB _power  = 10 log ₁₀ (P1  / P2)

 

Rule: 3 dB is twice the power, and 10dB is 10 times the power.

 

A voltage ratio for equal impedance is expressed as:

 

  dB _voltage = 20 log ₁₀ (E₁ / E₂ )

 

Rule: 6 dB is twice the voltage, and 20 dB is 10 times the voltage. Increasing the voltage by a factor of 1.4 (3 dB) doubles the power (3 dB)

 

Voltage measurements can be made by using a reference level:

 

0 dBmV = 20 log₁₀ (E / 1mV)

 

Rule: 40 dB (20 + 20) is 100 times the voltage (10 × 10).

 

Signal level measurements is other countries use a 1 microvolt reference:

 

0 dBμV = 20 log₁₀ (E / 1μV)

 

Rule: the difference between dBmV and dBμV is 60 dB (0 dBmV equals 60 dBμV).

 

 

Carrier/Noise Ratio (C/N)

 

C/N at the output of a single amplifier when the noise figure (NF) is known:

 

C / N₀ = Output Level- (-59.2 + NF + Gain)

 

To sum identical carrier/noise rations:

 

C/N_s = C/N – 10 log₁₀ N

 

To sum differing carrier/noise rations:

 

C/N_s = 10 log₁₀ ( 10 ^{–C/N 1 / 10} + 10 ^{–C/N 2 / 10}  + ….. + 10 ^{–C/N n / 10})

 

Carrier / noise ratio vs bandwidth:

 

Δ C/N = 10 log₁₀ (Bandwidth _{ref /}  Bandwidth _new)

 

C/N = carrier to noise expressed as a positive number

N = Number of equal contributors

NF = Noise Figure

G = gain

- 59.2 = thermal noise in 4 MHz bandwidth (dBmV)

 

Rule: Single amplifier C/N Improves by 1 dB with every 1 dB increase in the input signal level.

 

Rule: Total C/N worsens by 3 dB with every double in the number of amplifiers with identical C/N.

 

Cross Modulation Ratio (XM)

 

XM at the out put of a single amplifier operating at a given output level:

 

XM = XM _ref – 2 (Output Level – Reference Level)

 

To sum identical cross modulation rations:              

XM_s = XM – 20 log₁₀ N

 

 

To sum differing cross modulation rations:              

XM_s = 20 log₁₀ ( 10 ^{–XM 1 / 20} + 10 ^{–XM 2 / 20}  + ….. + 10 ^{–XM n / 20})

 

Cross modulation vs channel loading:

 

Δ XM = 20 log₁₀ (Channel Load _ref –1 /  Channel Load _new-1)

 

XM = cross modulation expressed as a positive number.

 

Rule: Single amplifier XM improves by 2 dB with every 1 dB decreases in the output signal level.

 

Rule: Total XM worsens by 6 dB with every double in the number of amplifiers with identical XM.

 

 

Carrier / Composite Triple Beat Ratio (CTB)

 

CTB at the output of a single amplifier operating at a given output level:

 

CTB = CTB _ref – 2 (Output Level – Reference Level)

 

To sum identical Composite Triple Beat rations:              

 

CTB_s = CTB – 20 log₁₀ N

 

To sum differing composite triple beat rations:              

 

CTB_s = 20 log₁₀ (10 ^{–CTB 1 / 20} + 10 ^{–CTB 2 / 20}  + ….. + 10 ^{–CTB n / 20})

 

Composite triple peat vs channel loading:

 

Δ CTB = 20 log₁₀ (Number of Beats _ref  /  Number of Beats _new)

 

See page 69 to obtain the number of beats.

 

CTB = composite triple beat expressed as a positive number.

 

Rule: Single amplifier CTB improves by 2 dB with every 1 dB decrease in the output signal level.

 

Rule: Total CTB worsens by 6 dB with every double in the number of amplifiers with identical CTB.

 

 

 

 

 

 

 

 

Carrier / Single Second Order Ratio (SSO)

 

SSO at the output of a single amplifier operating at a given output level:

 

SSO = SSO _ref – (Output Level – Reference Level)

 

To sum identical single second order rations:              

CSO_s = CSO – 15 log₁₀ N

 

To sum differing single second order rations:              

 

CSO_s = 15 log₁₀ (10 ^{–CSO 1 / 15} + 10 ^{–CSO 2 / 15}  + ….. + 10 ^{–CSO n / 15})

 

SSO = single second order expressed as a positive number.

 

Rule: Single amplifier SSO improves by 1 dB with every 1 dB decrease in the output signal level.

 

 

Carrier / Composite Second Order Ratio (CSO)

 

CSO at the output of a single amplifier operating at a given output level:

 

CSO = CSO _ref – (Output Level – Reference Level)

 

To sum identical composite second order rations:              

 

CSO_s = CSO – 15 log₁₀ N

 

To sum differing composite second order rations:              

 

CSO_s = 15 log₁₀ (10 ^{–CSO 1 / 15} + 10 ^{–CSO 2 / 15}  + ….. + 10 ^{–CSO n / 15})

 

Composite second order vs channel loading:

 

Δ CSO = 10 log₁₀ (Number of Beats _ref  /  Number of Beats _new)

 

See page 69 to obtain the number of beats.

 

CSO = composite second order expressed as a positive number.

 

Rule: Single amplifier CSO improves by 1 dB with every 1 dB decrease in the output signal level.

 

 

Carrier / Composite Intermodulation Noise Ratio (CIN)

 

It is assumed that CIN is dominated by 3^rd order distortion (CIN₃). This is the case in systems with analog television channels to 550 MHz and digital video above 550 MHz.

 

CIN at the output of a single amplifier operating at a given output level:

 

CIN = CIN _ref – 2 (Output Level – Reference Level)

 

To sum identical composite intermodulation noise rations:              

CIN _s = CIN – 20 log₁₀ N

 

To sum differing composite intermodulation noise rations:              

 

CIN _s = 20 log₁₀ (10 ^{– CIN 1 / 20} + 10 ^{– CIN 2 / 20}  + ….. + 10 ^{– CIN n / 20})

 

To sum C/N and CIN:

 

C/N _s = 10 log₁₀ (10 ^{– C/N / 10} + 10 ^{– CIN / 10})

 

CIN = composite Intermodulation noise expressed as a positive number.

 

Rule: CIN behaves like CTB in a cascade of amplifiers, but it adds to the C/N.

 

Rule: Total CIN worsens by 6 dB, with every double in the number of amplifiers with identical CIN.

 

 

Carrier / Hum Modulation Ratio (C/H)

 

These calculations assume that all system power supplies are connected to the same power line phase.

 

To sum identical carrier / hum rations:

 

C/H = C/H – 20 log₁₀ N

 

To sum differing carrier/hum rations:

 

C/H _s = 20 log₁₀ (10 ^{– C/H 1 / 20} + 10 ^{– C/H 2 / 20}  + ….. + 10 ^{– C/H n / 20})

 

To convert percent hum to C/H:

 

C/H = 20 log ₁₀ (%Hum/100)

 

To cover C/H to percent Hum:

 

%Hum = 100 (10 ^{– C/H / 20} )

 

C/H = Carrier to hum expressed as a positive Number

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Linear Measure

 

 

 

 

Volume

 

 

 

Weight

 

 

Signal Levels

 

 

 

Miscellaneous

 

 

Prefixes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Wavelength and antennas

 

Vertical Antenna Separation

 

Antennas for differing frequencies mounted on a common mast should be separated by at least the length of the longest element of the largest antenna.

 

Wavelength

 

Wavelength is inches is given by:

 

λ = 11.811 / f (MHz)

 

Quarter Wave Whip Antenna

 

The approximate length in inches is:

 

λ / 4 = 2.775 / f (MHz)

 

Distance to Horizon

 

Optical: D = 1.23

Radio: D = 1.41

 

D= Distance in miles; H= observation height in feet

 

Velocity of Propagation

 

In free space RF propagates at approximately

186,000 mi/sec or 982 ft/μsec. To find the velocity in cable , use the multiplier given for the cable.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ohms Law

 

Ohms Law for dc Circuits:

 

Known	To Determine Value of:
Value	I	R	E	P
I and R	-	-	I × R	I 2 × R
I and E	-	E / I	-	E × I
I and P	-	P / I 2	P / I	-
R and E	E / R	-	-	E 2 / R
R and P		-		-
E and P	P / E	E 2 / P	-	-

 

I =current in Amperes                                         E= potential difference in Volts

R =resistance in Ohms                                       P= power in Watts

 

 

Resistors in series: R_T = R₁ + R₂

 

Two resistors in parallel:  R_T =

 

More than two resistors in parallel:

 

R_T = 1/1/R₁ + 1/ R₂ +..+1/R_n

 

Power factor: pf= True Power (W) / Apparent (E ×I)