Presents Practical Applications of RF Wireless Systems

1
PresentsPractical ApplicationsofRF Wireless
Systems
2
Preview

• The Invisible Stuff
• RF Signals
• A Trip Down The Congested RF Highway
• DTV
• Multiple-System Operation
• Frequency Compatibility and Coordination
• Solid Rules of Thumb
• Maximizing the Potential of your Hardware
• Transmitters
• Receivers
• Antennas
• RF Boosters and Splitters

3
PART 1The Invisible Stuff
4
RF Microphone Signals
Audio Signal Is modulated via FM with
RF Carrier Frequency Expressed in
MHz (Megahertz) Can be either VHF or UHF
Transmitted RF Signal
5
RF Spectrum Divisions (highways)

• RF Wireless Microphone Usage (large macro range)
• 54 MHz 950 MHz
• Conveniently divided up into TV Channels (lanes)
• 6 MHz wide
• Disproportionately grouped into zones (highways)
• VHF (12 TV Channels)
• 138 MHz wide
• 54 MHz 192 MHz
• UHF (80 TV Channels)
• 480 MHz wide
• 470 MHz 950 MHz

6
Any given RF carrier (center frequency)
falls inside of an NTSC TV
channel Knowing where
youre operating is essential
7
USA TV CHANNELS V/S BANDWIDTHS
8
ANATOMY OF AN ANALOG TV SIGNAL example channel 19
Lower Edge 500.000 MHz
Upper Edge 506.000 MHz
0 amplitude
Video Carrier center freq 501.250 MHz
Color Carrier center freq 504.830 MHz
Audio Carrier center freq 505.750 MHz
9
Historically

• VHF Systems were first on the scene
• Plus Side
• Affordable technology
• Good S/N Ratio
• Good AF bandwidth potential
• Down Side
• Limited RF Bandwidth
• 12 TV Channels wide
• Very competitive for open, unused frequencies
• Generally fixed-frequency systems

10
At That Point

• UHF Systems were generally cost-prohibitive
• Plus Side
• Huge bandwidth potential (80 TV channels)
• The UHF highway has 6 times more lanes
• Better potential for multi-channel systems
• Far better potential for open, unused
  frequencies
• Down Side
• Very expensive technology at the time
• Very high cost to produce good S/N ratio
  technology
• Very high cost to produce good AF bandwidth
  potential
• Generally fixed-frequency systems
• But very attractive

11
Trending Onward

• UHF Systems become more affordable
• Plus Side
• Huge bandwidth potential (80 TV channels)
• The grass is greener syndrome
• The UHF highway has 6 times more lanes
• In any given area there might have been 10 15
  active UHF broadcasts much fewer in less
  metropolitan areas
• Far better potential for open, unused
  frequencies
• Down Side
• Most were still fixed frequency systems
• Switchable channel systems were still very
  expensive

12
The Promised Land

• UHF Systems become the standard
• Plus Side
• Huge bandwidth potential
• Finding an open frequency is like shooting ducks
  in a barrel
• High S/N ratio technology becomes affordable
• High AF bandwidth technology becomes affordable
• Switchable frequency system technology becomes
  affordable
• Frequency agility becomes the industry catch
  phrase
• Multiple system operation becomes a standard
• Life is swell

13
Until DTV

• Advancements in Television Technology go Digital
• Worldwide television standard shall be digital
  by 2006
• A change like this cant take place overnight
• A 10 year plan is put into effect
• Based on life cycle of TV broadcast and receiving
  equipment
• All TV broadcasts shall be digital by 2006
• Meanwhile, all TV broadcasters are assigned a
  co-channel to begin transmitting their digital
  signals on
• Effectively doubling the occupied UHF channels

14
What DTV has done to your local RF environment
15

• LOS ANGELES
• VHF TV
• WWW.100000WATTS.COM

16

• LOS ANGELES
• UHF TV

17
LOS ANGELES UHF TV in the UHF SPECTRUM
18
ANATOMY OF A DIGITAL TV SIGNAL example channel 19
Lower Edge 500.000 MHz
Upper Edge 506.000 MHz
0 amplitude
Video, Color and Audio Carrier Signals Are
Scattered Throughout the Bandwidth at FULL
Amplitude
19

• MULTIPLE-SYSTEM OPERATION
• Coordinating your systems
• for simultaneous use
• Whether youre shooting sound on a film set,
  touring with rock act, staging a theatrical
  production, or installing a wireless system in a
  venue, chances are that your wireless system will
  include more than one unit.

20

• TV Broadcast signals
• Since you cant beat em Avoid em
• FREQUENCY AGILITY
• The most important element in having the hardware
  to do the job.
• Frequency-agile systems give the user the ability
  to change the carrier frequency that a system
  operates on.
• The only effective line of defense in dodging
  active UHF signals

21

• FREQUENCY COMPATIBILITY

22

• A Functional Multi-Channel RF System Is Like A
  Really Good Neighborhood Living In Harmony

• Active Frequencies that Live Together Must Agree
• Mathematical elements may clash (conflicts)
• Center Frequency Must Agree
• No Common Exponential Convergence
• Harmonic Content Must Agree
• No Common Exponential Convergence
• Intermodulation
• Second, Third and Fifth order harmonics clash
• Harmonic content must be in agreement

23

• Good Rules of Thumb
• Know your local RF Environment
• Collect all available info on UHF frequency
  occupation
• UHF TV broadcasts within a 75 mile radius
• FCC Web site
• 100000watts.com
• Local US Post Offices should have a listing
• Determine other sources of RF signals in
  operation and what carrier frequencies are in use
• Other wireless microphone and monitoring systems
• Walkie-Talkies
• Short wave communications
• Plan your frequency allocations according to that
  info
• Draw a map of the RF scale using TV channel lines
  of demarcation
• Disqualify occupied TV channel choices with an X
• Plan your frequency targets by good or no
  good TV channels
• Follow the manufacturers frequency grouping
• Theyve done the math Take their word for it

24

• Good Rules of Thumb (cont)
• If you Ad Lib your frequency schemes
• you must know what youre doing.
• Its all about interval logic
• An interval is the distance between two points in
  time or space
• Never choose an interval thats less than 400 KHz
• Commonly called minimum spacing
• Never repeat an interval
• Causes common (repetitive) mathematical elements
• Use the manufacturers published intervals as a
  guide or template
• Allows a logical scheme that can be shifted up,
  or down the frequency spectrum
• Chances are that these choices will prove
  effective

25

• Example of Shifting the Intervals

26
8 Compatible Frequencies within ONE TV
Channel Given that TV Channel 23 (524 530 MHz)
is Target A
27
16 Compatible Frequencies within TWO TV
Channels Given that TV Channel 23 (524 530 MHz)
is Target A And TV Channel 42 (638 644 MHz) is
Target B
28
Fitting 3 frequencies inside an active NTSC
Channel example channel 19
Formula f1 edge 3.2 MHz, f2 edge 3.6
MHz, f3 edge 4.3 MHz All 3 are intermod
free and compatible with other carriers
f1
f2
f3
Lower Edge 500.000 MHz
Upper Edge 506.000 MHz
0 amplitude
Video Carrier 501.250 MHz
Color Carrier 504.830 MHz
Audio Carrier 505.750 MHz
29
PART 2Optimizing your Hardware
30
Transmitters
31

• A transmitters job is quite simple
• Converts incoming audio source signal into a
  radio signal
• 2) Sends it out into open space via its antenna

32

• Wireless Microphone Transmission
• Audio Source
• Microphone Diaphragm
• Handheld Transmitter with Microphone Capsule
• Lavalier Microphone
• Suitable Line Signal Source
• Pre-Emphasis Circuit
• Compander (Compression/Expansion) (Noise
  Reduction)
• 21 Compressor
• Limiter
• Oscillator
• RF Output Amplifier

33

• Two main variable components of a transmitter
  that will directly affect its performance
• Input sensitivity control
• A variable gain amplifier (pad) that determines
  the signal gain presented to the front end of the
  transmitter.
• Antenna
• Its condition determines the electrical
  conductivity
• Its positioning determines its ability to
  effectively radiate electro-magnetic energy
• Beware of grounding it to the body

34

• TRANSMITTER TYPES
• Handheld
• Integrated Microphone Capsule
• Dynamic
• Condenser
• Integrated Antenna

Integrated Capsule
Integrated Antenna
35

• TRANSMITTER TYPES (cont)
• Bodypack
• Complementary Input Device
• Lavalier or Headworn Microphone
• Line Input Cable
• Complementary Antenna
• Whip
• Helical

36

• Something New!

SK5012 Ultra-Miniature Transmitter
37

• TRANSMITTER TYPES (Cont)
• Plug-On Module
• Couples to Suitable Handheld Microphone
• Converts any handheld microphone into wireless
• Antenna is integrated into the chassis of the
  microphone
• XLR pin 1 (ground) carries antenna signal to mic
  chassis

38

• TRANSMITTER TYPES (Cont)
• Rack-Mountable
• IEM System Transmitter
• Transmits Complex Stereophonic Signal
• Generally uses
• Whip Antenna
• Paddle-style Log Periodic Antenna (remote mounted)

39

• Receivers

40

• RECEIVERS
• Receives, demodulates, processes, and outputs
  audio signal
• Front-End Filtering
• Selects the specific frequency range of the
  system
• Local Oscillator
• Facilitates separation of carrier signal from
  audio
• Expander
• 12 ratio
• Re-Establishes original dynamic range
• De-Emphasis
• Undoes the frequency-specific coding of the audio
  signal
• Audio output amp
• Line level
• Mic level

41

• Two main variable components of a receiver that
  will directly affect its performance
• Squelch
• A variable gain amplifier that determines the
  presence or absence of audio signal processed by
  the receiver.
• Basically an audio path noise gate that is
  triggered by the signal strength (amplitude) of
  the RF carrier
• May play a significant role in system range
• Antenna
• Its orientation to physical and ethereal elements
  makes it function like the eyes of the receiver
• Its positioning determines its ability to
  effectively collect electro-magnetic energy

42

• RECEIVERS TYPES
• Rack Mountable or Fixed Location
• Used in stage and studio production
• AC Powered via
• Integrated internal power supply
• Remote Wall Wart AC-to-DC converter power supply

2 EW EMs can sit side-by-side in a 19 rack space
Without or With Headphone Monitoring
43

• EM550

• Dual Channel Receiver
• Integrated Active Antenna Splitter
• Integrated Power Supply

44

• RECEIVERS TYPES (cont)
• Portable or Camera-Mountable
• Used in field production for video and film
• IEM (In-Ear Monitor) Stereo Receivers
• DC powered

ENG
IEM
45

• QP3041 Quadpack

46

• RECEIVERS (cont)
• Non-Diversity
• Uses single antenna and receiving circuit
• Can be adversely affected by multi-path
  information
• True Diversity
• Uses dual antennas and receiving circuits
• Comparator circuit
• Analyzes incoming signals
• Chooses the strongest (most integrity) in
  microseconds
• Throughputs the chosen signal for processing
• Best defense for multi-path dropouts

47

• ANTENNAS
• and
• Antenna Accessories

48

• ANTENNAS
• Wideband
• Capable of capturing and conveying wide bandwidth
  UHF
• Must be followed by bandwidth filter
• Omnidirectional
• Directional
• Passive or
• Active
• Narrowband
• Cut to length to adequately convey desired
  bandwidth
• Receivers usually have filtering post-antenna
  anyway
• Omnidirectional
• Directional
• Passive or
• Active

49

• ANTENNAS
• Placement
• Out in the open if at all possible
• Avoid proximity to large reflective surfaces
• Probable source of multi-path information
• Directional
• Passive or
• Active
• Stock, telescoping whip type
• Mounts to receiver chassis
• Ground plane principal
• Orient at 90 degrees to one another for best
  performance
• Specific operating principal antennas for remote
  mounting
• Away from the receiver
• Paddle-Style, Log-Periodic, or Yagi- Style
• Improves performance
• Reduces the transmitter-to-receiver differential

50

• ANTENNA TYPES
• Log Periodic Paddle-Style

51

• ANTENNA TYPES (cont)
• Ground Plane

52

• ANTENNA TYPES (cont)
• Yagi

53

• Antenna Boosters
• Frequency-selective active gain stage (10 to 18
  dB) to compensate for signal loss that occurs in
  a long antenna co-ax run
• Filtered for the specific desired bandwidth
• A very helpful device when using a splitter
  down-stream
• Antenna Splitters
• Allows RF from one pair of antennas to feed
  multiple receivers
• Makes for clean and efficient system performance
• Multiple splitters may be required for multiple
  frequency-range receiver systems

54
ANTENNA
ANTENNA
RF
A
B
A RF INPUTS B ANTENNA SIGNAL
SPLITTER A RF OUTPUTS B
A RECEIVER 1 B
A RECEIVER 2 B
A RECEIVER 3 B
A RECEIVER 4 B