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Digital Modes. RTTY, PSK31 , Packet, Pactor, Clover, Hellschreiber, MFSK, G-TOR, MT-63, Throb, Q15X25. PSK 31. Cousin of RTTY Excellent weak-signal performance Not error free. History. Created by Peter Martinez, G3PLX At first, not very popular because special DSP hardware was needed.

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digital modes

Digital Modes

RTTY, PSK31, Packet, Pactor, Clover, Hellschreiber, MFSK, G-TOR, MT-63, Throb, Q15X25

psk 31
PSK 31
  • Cousin of RTTY
  • Excellent weak-signal performance
  • Not error free
history
History
  • Created by Peter Martinez, G3PLX
  • At first, not very popular because special DSP hardware was needed.
  • 1999 - Peter designed a version of PSK31 that needed nothing more than a common computer sound card.
history1
History
  • Simple piece of software that ran under Windows.
  • Software available free on Internet
  • Uses soundcard interface to the transceiver.
history2
History
  • PSK31 exploded in the HF digital community.
  • Most popular mode for casual QSO’s.
  • PSK63 appeared in 2003 and is used by contesters.
what is psk31
What is PSK31?
  • PSK = Phase Shift Keying
  • 31 = bit rate (31.25 baud)

===========================

  • Compare to CW
    • Simple binary code
      • Short pulses (Dits)
      • Long pulses (Dahs)
      • Communicate the whole English language by combining strings of dits and dahs.
      • Gaps separate characters and words.
slide7
Compared to RTTY
    • Still binary
      • Instead of on/off (CW), shift frequencies (FSK)
      • 5 bits plus start and stop pulses.
  • PSK uses Varicode
    • Varying number of bits representing each character.
      • Shorter for often used characters
      • Longer for less often used characters
slide8
The letter “e” is used most often and gets a Varicode of 11, whereas, “E” gets a Varicode of 1110111
  • “z” gets very little use so it has a Varicode of 111010101; “Z” gets 1010101101
  • Gaps represented by “00”
  • Two zeros never get used in characters
a digital station
A Digital Station
  • What is needed?
    • Transceiver – most already have one.
    • Modem – many have them in the form of a computer soundcard.
    • Software – converts binary data from computer to modulated audio tones.
a digital station1
A Digital Station
  • Interface – the connection between the computer soundcard and the transceiver.
    • Audio from soundcard to transceiver
    • Audio from transceiver to soundcard
    • PTT
interface
Interface
  • Numerous available on the market
    • Rigblaster
interface1
Interface
  • RigExpert

SD

Standard

Plus

interface2
Interface
  • Tigertronics SignaLink

SL-1+

USB

interface3
Interface
  • Buxcomm Rascal GLX
interface4
Interface
  • Homebrew
interface5
Interface
  • NUE-PSK Digital Modem
      • A digital modem for PSK31 field operation ... without using a PC!
          • The NUE-PSK Digital Modem comes fully assembled and tested... just plug in your keyboard and SSB transceiver, and start operating!
      • www.amqrp.org
slide17
How do we generate BPSK signal and transmit Varicode over the airwaves?
    • Use DSP capabilities of soundcard
      • Create audio signal that shifts phase angle 180 degrees in sync with 31.25 bps data stream
      • “0” bit generates phase shift
      • “1” bit does not
      • Hence, Binary Phase-Shift Keying
slide18
When the BPSK audio signal is applied to an SSB transceiver we get BPSK modulated RF.
  • Only 31.25 Hz wide, narrower than CW.
  • Concentrating RF into narrow bandwidth produces good reception.
  • Receiving station must sync with transmitting station (Software)
  • Phase transitions are mathematically predictable due to the structure of Varicode.
psk31 software
PSK31 Software
  • Download off Internet:
  • Many are freeware or shareware with a requested donation.
  • Popular programs:
    • HRD/DM780 (IMHO, the best)
    • MixW
    • Digipan
    • MultiPSK
    • Others
psk31 setup
PSK31 Setup
  • Receiving (You should be hearing a PSK warbling sound. If not, check your sound card volume)
  • Panoramic display – waterfall
    • With no IF or AF filtering the bandwidth on the waterfall is about 3000Hz.
    • Bandwidth of BPSK signal is 31Hz.
    • Many PSK signal can fit in that spectrum
    • Vertical lines of varying color/intensity will be seen on the waterfall
    • Bright = strong, faint = weaker
slide21

ACTIVITY

  • PSK31 activity found on:
    • 160M 1807 kHz (USA)

1838 kHz (Europe)

    • 80M 3580 kHz
    • 40M 7070 kHz (USA)

7035 kHz (Europe)

7028 kHz (Japan)

    • 30M 10138-10142 kHz(Digital Only)
    • 20M 14070 kHz – most activity
    • 17M 18100 kHz
    • 15M 21070 kHz
    • 12M 24920 kHz
    • 10M 28120 kHz
    • 6M 50290 kHz (USA)

50250 kHz (Europe)

  • Let’s get started…
slide22
Park radio on frequency of your choice.
  • Frequency displayed is Suppressed Carrier Frequency (SCF)
  • USB – range is 2-3 kHz above SCF.
  • LSB – range is 2-3 kHz below SCF.
  • Example: Radio showing 14070 kHz USB
    • Receiving everything from 14070 to 14073 kHz.
    • Place cursor on vertical signal line and click.
    • Software selects and decodes the signal.
    • When you transmit, the software will generate a tone (warble) corresponding to the frequency of the selected tone.
slide23
Transmitting
    • Tone selected creates an RF signal on the correct frequency.
    • PSK31 is a 80-100% duty cycle mode.
    • Most operators run a 20-40% of maximum output.
    • Power level is adjusted by the level of the audio signal being fed to the input.
    • Most accepted procedure:
      • Set Power to max. (100W for most TRX)
      • Apply signal to audio input
      • Adjust level to 20-40% (20-40W)
    • Overdriving will cause splatter making your signal much wider than 31 Hz.
slide24
Overdriving
    • Indications
      • ALC will show activity. There should be no ALC indications.
      • Goal is to stay in the linear portion of the operating curve.
        • Some radios will become non-linear at 50% max.
        • This is not as noticeable with SSB voice signals
        • Shows up as splatter in PSK31 mode.
      • Use IMD (Intermodulation Distortion) meter
        • Good signal shows IMD of <-20 db
        • Ideally, <-23
    • Overdriving can alsoburn out you final transistors
digital signal reporting
Digital Signal Reporting
  • RSQ Reporting
    • Readability
    • Strength
    • Quality
    • Although not yet accepted in Region 2, it has been in Regions 1 & 3 and it is being used by some stations in the US.
    • It more accurately indicates the quality, as well as, strength of the PSK signal.
    • Go to www.rsq-info.net for more informaiton.
slide27
Readability
    • R5 95%+ Perfectly readable
    • R4 80% Practically no difficulty, occasional missed characters
    • R3 40% Considerable difficulty, many missed characters
    • R2 20% Occasional words distinguishable
    • R1 0% Undecipherable
  • Strength
    • S9 Very strong trace
    • S7 Strong trace
    • S5 Moderate trace
    • S3 Weak trace
    • S1 Barely perceptible trace
  • Quality
    • Q9 Clean signal – no visible unwanted sidebar pairs
    • Q7 One barely visible pair
    • Q5 One easily visible pair
    • Q3 Multiple visible pairs
    • Q1 Splatter over much of the spectrum
resources
Resources
  • ARRL’s HF Digital Handbook, Third Edition by Steve Ford, WA8IMY
  • Websites:
    • www.westmountainradio.com
    • www.rigexpert.com
    • www.tigertronics.com
    • www.buxcomm.com
    • www.geocities.com/n2uhc/interface.html
    • http://forums.ham-radio.ch/ (HRD)