Transcript No Slide Title

NBEMS
Narrow Band Emergency Messaging System
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
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
NBEMS
Narrow Band Emergency Messaging System
Is software
Fldigi – digital modem program
Flarq – automated repeat request program
Wrap – file encapsulation program
Which Runs on - Xp
Lenovo Netbook
Which Runs on - Vista
Compaq Notebook
Which Runs on - Linux
Acer Aspire / Ubuntu 9.04
Which Runs on – Puppy Linux
Compaq Notebook – thumb drive boot
Which Runs on – OS X
Apple
Hardware
•Windows, Linux or Mac OSX Computer
Hardware
Sound Card Interface & Transceiver
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.
Hardware
Sound Card Interface
SignaLink SL-1+
Geeks.com $5
USB audio-codec
A Homebrew Interface
For homebrewing, a blank PCB is
available for $5.00 and a SASE
from Skip, KH6TY
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.
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 QSO’s would be impossible!
 Emergency Communications
 You already have 99 % of the equipment – nothing expensive to buy
 It’s FUN

Digital Waterfall
Is a visual representation of time, frequency and amplitude
frequency
time
Color == Amplitude
•Blue = low amplitude
•Yellow = medium amplitude
•Red = high amplitude
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!
Audio Level Settings
Turn 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 the
audio passband of the receiving stations!
Good
A bad neighbor
Overdrive also increases the error rate at the receiving station
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
Audio Level Adjustment
Turn off the tune signal and try sending
a 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
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 external
standard 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 other
station 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)
Sound Card Calibration
WWV method
Select the WWV operating mode and tune the radio
to WWV at 5, 10 or 15 MHz.
Use USB or AM mode on the radio
The waterfall looks like
Sound Card Calibration
WWV time tick
NBEMS
DominoEX-11
Preferred
MFSK-16
Modes
Olivia 16/500
MT63-1000
DominoEX11
DominoEX11 provides excellent keyboard to keyboard communications. It is excellent on HF
when conditions are poor to good. This mode provides a reliable means of sending and receiving
short messages. Tuning is not critical.
MFSK-16
MFSK16 is a multi-frequency shift keyed. It has low symbol rate and a single carrier
of 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.
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.
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 used
detailed 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.
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.
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.
Automated Repeat Request
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
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 as
they are received.
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/group/NBEMSham/