SSTV

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SSTV

• Patrick Innes W4TQI

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What is SSTV?

• Slow Scan Television
• Method of sending still images by radio

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SSTVs Many Modes

• SSTV is actually many different modes that all
  do about the same thing
• Scottie 1 / 2 / DX
• Martin 1 / 2
• Robot 24 / 36 / 72
• BW 8 / 12
• Digital SSTV not really related

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Sample Pictures

• Quality of received picture depends on mode used,
  signal strength, and band conditions

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• What sorts of images are sent via SSTV?

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Pictures of Hams
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Their Gear
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Their Families
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Scenery
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Where They Live
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Cartoons
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Space
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Other Hobbies
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Almost Anything!
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Most Practical Application

• Emergency Services Damage Assessment

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A Bit Of History

• Early SSTV hardware was scratchbuilt, using
  long-presistence radar CRTs
• Pictures generated live with flying-spot
  scanners or vidicon tubes

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Hardware-based SSTV

• Eventually, commercial hardware became available
• Specialized
• Expensive
• Only a few modes
• per unit

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Recent Hardware

• 1990s Kenwood released the VC-H1
• Replaced mic on Kenwood radios
• Complete SSTV station in one
• compact unit
• Digital camera
• LCD screen
• Hand mic/speaker
• Supported several
• popular modes

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Todays SSTV Hardware

• 100 MHz computer
• Windows 95 or later
• 32 MB of RAM
• 16-bit sound card
• Transceiver
• Some sort of interface
• (optional)

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SSTV Software

• Several shareware and freeware packages available
• Most use sound cards DSP features to process the
  audio signal
• Most software allows operation of many different
  modes

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Available Software

• MMSSTV
• Freeware
• Most popular
• MixW
• Shareware (50)
• Many digital modes
• ChromaPix (120)
• Linux QSSTV
• Mac MultiMode

MMSSTV MixW
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Possible SSTV Problems

• Slant
• Phase
• Tearing
• Doubling
• QRM
• D.O.M.S.

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Slant

• Results in slanted or skewed image
• Caused by one or both stations being improperly
  calibrated
• Most software is easy to calibrate to WWV
• One properly calibrated computer can be used to
  calibrate another if no time standard signal is
  available
• Software can compensate for some slant, but its
  best to be calibrated

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Slanted Pictures
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Phase / Tearing

• Caused by a stall or interruption of the transfer
  process
• Often originates in the sending machine, but can
  be caused on the receiving end
• Most common causes
• Other programs running at the same time
• Not enough RAM or processor to handle the load

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Torn Pictures
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Doubling
Doubling

• Two or more stations transmitting at the same
  time
• SSTV is timing-critical, and two signals will
  never be exactly in sync with each other
• Result depends on relative signal strengths
• From starting over with the stronger signal to
  unreadable images

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Doubled Images
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QRM

• Disrupts SSTV just as much as it does other forms
  of communication
• Tune-ups on frequency
• Calling CQ on the SSTV frequencies
• Contests
• Accidental transmissions

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QRMed SSTV Images
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D.O.M.S.

• Dirty Old Man Syndrome
• Never know who will be watching
• Public Demos
• School Stations
• Scout Troops
• Just as with other modes/bands, some people dont
  play well with others
• Result Cheesecake Pictures

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D.O.M.S.
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D.O.M.S.

• Problem isnt too widespread
• Most hams will refrain if asked nicely
• Usually just a handful of operators
• Remember

Every time you transmit, you are representing
amateur radio to the public!
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So Wheres the SSTV?

• Many frequencies allocated, but most activity is
  on 20 meters at 14.230 MHz

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SSTV on 2 meter FM

• Most SSTV activity happens on HF SSB, but it will
  work on any technology that can transmit 1200
  2300 Hz tones
• Telephone
• Open air
• Tin cans and string
• 2 meter FM

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SSTV on 2 meter FM

• Last year, we experimented with 2m simplex SSTV
• Excellent results
• Stronger signals with less fading than SSB

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SSTV on 2 Meter FM

• Simplex usually found around 145.500 MHz
• SSTV nets operate on voice repeaters
• Dedicated repeater activity within normal voice
  repeater frequencies