NBEMS Narrow Band Emergency Messaging System

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 Developers

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 The Support Team

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-31OliviaMFSK-16 Low Power - never need to run over 50 watts, 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 time frequency Color == Amplitude Blue = low amplitude Yellow = medium amplitude Red = high amplitude Is a visual representation of time, frequency and 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! GoodA 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 method

Sound Card Calibration using CheckSR CheckSR is a free program that makes the calculation for your sound card offset error. Run the CheckSR application for your sound card native sampling rate. Let the program run for about 5 minutes, then click stop and record the numbers. Enter these values into the fldigi PPM controls Output Input

NBEMS Preferred Modes DominoEX-11 MFSK-16 Olivia 16/500 MT

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 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 ModeSpeedDuty CycleBandwidthLinear Path DominoEX-1180 wpm100 %262 HzNO (1) MFSK-1658 wpm100 %316 HzNO (1) Olivia 16/ wpm100 %500 HzYes (2) MT wpm80 %1000 HzYes (3) MT WPM80 %2000 HzYes (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: WPA NBEMS Site: CheckSR Sound Card Calibration Application: Fldigi on-line help: Fldigi on-line mode identification – sight and sound NBEMS official list: