NBEMS

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NBEMS Narrow Band Emergency Messaging System
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The Developers
W1HKJ Dave, licensed for 52 years Retired
USCG, MSEE, 40 years in software dev. Expert in
nothing, but works hard in digital mode
code M0GLD Stelios, licensed 8 years MSCE,
doctoral candidate Expert in cross platform
development 30 years old KH6TY Skip, licensed
56 years Electronics entrepreneur inventor of
WX alert radio Developer of Digipan Human
interface design WA5ZNU Leigh, licensed since
1968 (7 years old) Expert in all things
xml F8CFE Stephane Originator and principal
developer of hamlib
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The Support Team
W3NR Ed, Extra Class CW / RTTY digital modes
op Retired USPS New Installs RigCAT Hamlib
support Patience of an angel supporting users
since version 1.0 WA4SXZ Rich licensed since
1965 elmer for XP/Vista/Linux installations,
esp' Yaesu rigs KB3FXI Dave NBEMS support W3YJ
Harry NBEMS support Many others who help in
specific areas
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NBEMS Narrow Band Emergency Messaging System Is
software
Fldigi digital modem program Flarq automated
repeat request program Wrap file encapsulation
program
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Which Runs on - Xp
Lenovo Netbook
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Which Runs on - Vista
Compaq Notebook
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Which Runs on - Linux
Acer Aspire / Ubuntu 9.04
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Which Runs on Puppy Linux
Compaq Notebook thumb drive boot
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Which Runs on OS X
Apple
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Hardware

• Windows, Linux or Mac OSX Computer

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Hardware Sound Card Interface Transceiver
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Sound Card Interface

• Connects computer sound card to the radio
• Provides RF isolation
• Provides ground loop isolation (transformer
  coupling)
• Can automate the PTT when you transmit.

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Hardware
Sound Card Interface
Geeks.com 5 USB audio-codec
SignaLink SL-1
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A Homebrew Interface
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For homebrewing, a blank PCB is available for
5.00 and a SASEfrom Skip, KH6TY
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Hardware

• Windows, Linux or Mac OSX Computer
• Transceiver
• Sound Card Interface
• Or, maybe just a 8 computer microphone

To start playing around... all you need is an
inexpensive computer microphone! Just plug a mic
into your sound card mic input and place the mic
element somewhere near your radio speaker.
Listen and watch your display and practice
differentiating the various modes.
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Why Use Digital Modes
PSK-31
Olivia
MFSK-16

• Low Power - never need to run over 50 watts,
  5 -30 watts is almost always sufficient
• Reliable communications succeeds even when CW
  fails some modes work below -8 dB s/n
• Many modes - choose your mode depending on
  conditions
• Bottom of the solar cycle - works well, even
  under very poor conditions where phone QSOs
  would be impossible!
• Emergency Communications
• You already have 99 of the equipment nothing
  expensive to buy
• Its FUN

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Digital Waterfall
Is a visual representation of time, frequency and
amplitude
frequency
time

• Color Amplitude
• Blue low amplitude
• Yellow medium amplitude
• Red high amplitude

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Recommended Digital Modes for EmComm with the
NBEMS Software Suite

• DominoEX-11 fast turn around time, good for
  moderate to severe HF conditions and non-mission
  critical messaging, impervious to transceiver
  tuning
• MFSK-16 moderate speed, works under severe HF
  conditions, requires accurate and stable
  transceiver tuning.
• Olivia 16/500 slow but very accurate under poor
  HF conditions
• MT63 1k/long interleave relatively fast and
  best suited for detailed situation reports and
  formal messages under moderate to good HF
  conditions
• MT63 2k/long interleave very fast and extremely
  effective on VHF/UHF FM

Accuracy, speed and audio bandwidth all come into
play and various modes all have their advantages
and disadvantages!
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Audio Level SettingsTurn that thing down!
Distortion and non-linear operation (splatter) is
caused by overdriving your sound card audio into
your radio and it causes severe interference to
other stations within theaudio passband of the
receiving stations!
Good
A bad neighbor
Overdrive also increases the error rate at the
receiving station
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Audio Level Adjustment

• Set your radio RF output to it's maximum power
  level
• Adjust your sound card mixer master volume to
  minimum
• Set your radio meter to ALC (automatic level
  control)
• Click the Tune button on fldigi
• Increase your mixer volume control until the ALC
  meter begins to register
• Back off until no ALC
• Reduce the audio drive (or the transceiver power
  level) for the desired output level
• You will have just about a perfect transmit
  signal for ALL modes that fldigi produces

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Audio Level Adjustment
Turn off the tune signal and try sendinga PSK-31
idle signal (no keyboard input) You should see
your power meter fluctuate. As you send text the
fluctuation will increase.
This is your goal IMD -30 dB
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Sound Card Calibration

• Sound card accuracy is most critical on MFSK,
  Olivia and MT63.
• The errors between your sound card transmit and
  receive clock and an externalstandard is
  measured in parts per million (PPM) based on a
  given sample rate.
• If there is a discrepancy between your Tx and the
  receiving ends Rx sample rate, the result is
  the person on the other end of the QSO may not
  properly decode your transmitted text
• If there is a substantial difference between your
  Rx and Tx sample rates the otherstation may have
  to tune your signal after every exchange.
• Two ways to calibrate
• By receiving WWV - best
• By using a third party software which calibrates
  sound card to computer clock (OK if your
  computer clock is very accurate)

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Sound Card Calibration WWV method
Select the WWV operating mode and tune the
radioto WWV at 5, 10 or 15 MHz.Use USB or AM
mode on the radio
The waterfall looks like
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Sound Card Calibration WWV time tick
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NBEMS Preferred Modes
DominoEX-11
MFSK-16
Olivia 16/500
MT63-1000
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DominoEX11
DominoEX11 provides excellent keyboard to
keyboard communications. It is excellent on
HFwhen conditions are poor to good. This mode
provides a reliable means of sending and
receiving short messages. Tuning is not
critical.
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MFSK-16
MFSK16 is a multi-frequency shift keyed. It has
low symbol rate and a single carrierof constant
amplitude which is stepped between 16 tones. As
a result, no unwanted sidebands are generated,
and no special amplifier linearity requirements
are necessary. This is one of the few modes
that you can overdrive without fear of
splatter. This mode uses full-time Forward Error
Correction, so it is very robust. Tuning must be
very accurate, and the software will not tolerate
differences between transmit and receive
frequency. The mode was designed for long path
HF DX, and due to its great sensitivity is one
of the best for long distance QSOs and schedules.
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Olivia 16/500
Olivia 16 tones, 500 Hz mode is good for formal
short message handling. Although the mode is
relatively slow (about writing speed), it is very
accurate, even under extremely poor
conditions.Accurate decoding can occur when the
signal can be neither seen nor heard. A large
amount of forward error correction is utilized in
this mode, making it suitable for mission
critical messaging when used by properly trained
operators. Sound card calibration is critical,
but once the proper calibration procedures are
performed, the settings are saved and accuracy is
retained without the need for further
adjustments, unless the sound card is replaced.
See the QST article in the December 2008 issue
for a very good explanation of just how well this
mode performs under even the worst HF conditions.
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MT63 1k, Long Interleave

• MT63 1k long is ideal for portable, mobile and
  fixed station operations on HF and for use with
• VHF/UHF ssb. It provides good decoding under
  moderate to good s/n conditions. It can be
  useddetailed situation reports and database
  transmissions on VHF for the following reasons
• Very effective under moderate to good RF
  conditions
• Extremely accurate decoding (major duplication of
  data and forward error corrected)
• Works extremely well under QRM and QRN
  conditions
• Can be used with audio coupling but direct
  interfacing is recommended for all digital HF
  operations
• Tuning procedures and sound card calibration are
  critical with MT63 on HF, so the mode requires
  some training and practice. But once the use of
  the mode is mastered, it is extremely efficient.
  The speed at which MT63 1k long operates, makes
  it possible to send detailed reports that would
  not be practical using voice transmissions at
  writing speed.
• This mode required a very linear transmit /
  receive transmission path.

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MT63 2k, Long Interleave

• MT63 2k long is an excellent choice for local
  portable, mobile and fixed station operations on
  FM channels (repeater or simplex). It is
  extremely well suited for detailed situation
  reports and database transmissions for the
  following reasons
• Can be used very effectively without a sound
  card interface (audio coupling)
• Extremely effective, even under very poor
  simplex RF conditions
• Extremely accurate decoding (major duplication
  of data and forward error corrected)
• Very forgiving on sound levels and requires no
  tuning when used on FM
• Excellent for sending larger situation reports
  or databases
• MT63 2k long has been in use in Western
  Pennsylvania in several drills and public service
  events since 2005. The mode performs extremely
  well even under very adverse conditions. The
  fact that all one needs is a hand held
  transceiver and a computer (no need for sound
  card interface or any other hardware) makes the
  widespread adoption of this mode, for use on FM
  simplex and repeaters, a very attainable goal.
• This mode requires a very linear transmit /
  receive transmission path.

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Mode Comparison
Mode Speed Duty Cycle Bandwidth Linear Path
DominoEX-11 80 wpm 100 262 Hz NO (1)
MFSK-16 58 wpm 100 316 Hz NO (1)
Olivia 16/500 19.5 wpm 100 500 Hz Yes (2)
MT63-1000 100 wpm 80 1000 Hz Yes (3)
MT63-2000 200 WPM 80 2000 Hz Yes (3)
(1) a non-linear amplifier can be used for these
modes (2) required to maintain corrected phase
transitions between tones (3) required to
maintain correct amplitude/phase in signal
MT63 is essentially 64 simultaneous PSK signals
spread across the bandwidth of the signal.
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Automated Repeat Request
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Flarq

• Ancillary program acts as a client to the modem
  program
• Transfers blocks of data with checksums
• Blocks are automatically repeated if not
  confirmed
• Sending and receiving stations are locked in a
  handshaking mode during the entire transfer.
• Does NOT compensate for s/n ARQ requires a good
  to excellent signal path.
• It does provide absolute confirmation of receipt.
• Cannot be used for broadcast type transmissions.
• Requires either fldigi or MultiPsk for the modem
  transport layer

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Wrap

• File encapsulation for broadcast transmissions.
• A single application both wraps and unwraps
  transmitted files
• Allows for unattended reception of broadcast
• Ideal for transferring columnar data such as a
  spreadsheet
• Enables the transfer of plain text, image and
  binary files
• Verification of accuracy occurs at each receiving
  station
• Very simple to use drag and drop files for wrap
  / unwrap
• Can be used with any digital modem program
  program must not alter the ASCII characters
• Fldigi can automatically capture and save
  wrapped files asthey are received.

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Here are some useful links to sites with more
information on NBEMS Official NBEMS
Site http//www.w1hkj.com WPA NBEMS
Site http//www.pa-sitrep.com/NBEMS CheckSR
Sound Card Calibration Application http//www.pa-
sitrep.com/checksr/CheckSR.exe Fldigi on-line
help http//www.w1hkj/FldigiHelp Fldigi on-line
mode identification sight and
sound http//www.w1hkj.com/FldigiHelp/Modes NBEMS
official email list http//groups.yahoo.com/grou
p/NBEMSham/