Many years ago in a Galaxy not far away….

• DOD decided MARS volunteers must exclusively use a digital mode that military radios are capable of.

• Choices were RTTY, M110A single tone, M110A Appendix B 39 Tone modem.

• The decision was for M110A using free software. And the capability of MARS volunteers to pass traffic was degraded.

• Far more retransmissions were needed, and sometimes even after many retransmissions the message could not be passed. This despite the stations hearing each other well via SSB Voice.

What is a communications failure?

• In the distant past when two stations could not pass traffic by voice, they used the first digital mode called Morse Code.

• Later computer based digital modes were developed which are far superior to Morse Code.

• When two stations can communicate well by SSB Voice, yet can not pass a message digitally, this is a communications failure. The digital mode’s performance is worse than Morse Code, and worse than SSB Voice.

• MARS nets have frequent communications failures due to the mandatory use of M110A with the free software.

What are the M110A problems

• Most amateur radios do not have compatible Transmit and Receive bandwidths – discussed later.

• The Free Software has problems – discussed later.

The M110A bandwidth problem

• M110A at all its speeds, transmits 2400 symbols per second. Is not legal on the US HF amateur bands.

• Academic sources say it should operate in a 2400 HZ bandwidth if ideal theoretical infinite raised cosine filters are used.

• My DSP expert: “You need about 1.3 x the symbol rate. If you restrict the bandwidth the eye closes and the BER will increase for a given S/N eventually would won't be able to decode anything.” 2400 x 1.3 = 3120 HZ bandwidth.

• M110C C.5.1.4 “A square root of raised cosine filter is recommended with a roll off factor (excess bandwidth) of 35%. 2400 * 1.35 = 3240 HZ bandwidth.

Square Root Raised Cosine Filter

• https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120008631.pdf

• The rolloff factor is a measure of the excess bandwidth of the filter, i.e., the bandwidth occupied beyond the Nyquist bandwidth of 1/2T, where 1/T is symbol rate.

• As rolloff increases eye in the eye diagram opens up. This means that if there were no bandwidth restrictions it would be easier on the receiver if one used a large rolloff. (However, for bandwidth efficiency rolloff should be smaller.)

M110A bandwidth 300 to 3300 HZ?

• Amateur Radio digital modes are centered at 1500 HZ. M110A is centered at 1800 HZ.

• M110A needs 3000 HZ of bandwidth. • Centered at 1500 HZ, that is 0 to 3000 HZ. • Centered at 1800 HZ, that is 300 to 3300 HZ. • How many amateur radio models can transmit and receive

from 300 to 3300 HZ? • I only know that the expensive Flex and F8101 radios can

do it. • The F8101 overheats & shutdown - needs optional fan.

Noisy fan needs remote mounting kit & separation cable.

Bandwidth problems on our Nets

• Amateur Radio filters are centered at 1500 HZ in the radio hardware. This can not be changed.

• There are many MARS members using radios with a TX and RX bandwidth of 2900 HZ. 50 to 2950 HZ.

• There are many MARS members using radios with a TX and RX bandwidth of 2700 HZ. 150 to 2850 HZ.

• There are many MARS members using radios with a TX and RX bandwidth of 2400 HZ. 300 to 2700 HZ.

• They think their equipment is great – because they can pass traffic “some of the time” or maybe “most of the time” under good conditions.

• Even during ideal conditions, we are using M110A’s FEC to get any traffic passed. During worse conditions we fail.

Do military radios filter 300-3050?

• I have found on the internet some references to military radio filters limiting bandwidth 300-3050 which is 2750 HZ of bandwidth, centered 1675.

• Stanag 4538 “in a nominal 3 kHz bandwidth.(300 - 3050 Hz).”

• http://wireless.nmsu.edu/hf/papers/WBHF.pdf “the passband provided by current military radios extends from 300 to 3050 Hz. ”

• If true, then a 2.7Khz bandwidth amateur radio when using M110A centered at 1500 hz should perform nearly as well as a military radio.

• However, M110 itself uses 3240 HZ bandwidth.

Why will unacceptable radios work?

• Unacceptable radio works – some of the time.

• M110A 2400bps and lower speeds have FEC and repeating of data bits, which make it sometimes work with our inferior amateur radios’ bandwidth.

• But, often it will not work at all.

• It is unreliable.

What’s wrong with the free s/w

• I am not going to list everything wrong with the free s/w. • The biggest problem is its author has no knowledge of

how to write real-time software. • The shorter the message the more likely it will get passed

properly. • The faster the speed used, the more likely it will get passed

properly. • Station Manager added “send by page” because the free

software can not send medium sized messages – will always fails.

• The free software randomly crashes/dies. • Even after a decade of development, these characteristics

of the free software are INSANE.

Stuck with M110A, how can we make things better?

• Use TheModem software - written by a s/w professional with ample real-time programming experience.

• Center the modem software at 1500 HZ – Military stations will need to lower their frequency by 300 HZ to receive Mars’ M110 traffic.

• This adds 300 HZ of bandwidth to all amateur radios. Still most radios will not be 0 to 3000 HZ, but this will help.

• The vast majority of our amateur radios are not suitable for M110A. All we can do is try to make things better.

• Since DOD was not going to buy us military radios and hardware modems, the M110A decision degraded operations.

• Most members can not afford Flex or F8101 radios.

How my Kenwood TS590 does it

• Set my RX to 0 to 3400 HZ (0 to 3300 HZ RX not an option) • Set my TX to 10 to 3000 HZ (widest TX supported) • Set TheModem to center M110A at 1500 HZ. • Enable TheModem’s +/- 375 frequency offset which allows

reception of M110A centered at either 1500 or 1800 HZ. • When transmitting M110A, Enable radio’s XIT at +300 HZ. • Even though TX is centered at 1500, the +300 HZ XIT makes

it look like it is centered at 1800 to the receiving stations. • Turn 300 HZ XIT off during SSB voice transmissions. • Turn 300 HZ XIT on during M110A transmissions. • Not very helpful because all stations I communicate with

are not capable of 300 to 3300 HZ bandwidth.

TheModem’s author

• Has 5 years of real-time programming experience writing command/telemetry processing software for the $100,000,000 TDRS satellite.

• Has 8 years of real-time programming experience in process control – controlling Bethlehem Steel productions lines which produced $10,000 to $30,000 of profit per hour.

• Worked with BDM Corporation building the ROCS control system for the Washington DC’s WMATA subway system.

TheModem Features

• Provides MT63 500/1000/2000 and its own MT63 2700 true 8-bit mode.

• Provides MT63 “Sync Lock” which eliminates almost all false garbage character detection and printing.

• Provides Olivia 2000-32, 1000-32, and 500-32 modes. • Provides M110A 75bps to 4800 bps short or long interleave. • Tolerates maximum frequency offset of +/-375 HZ. (M110

spec is +/- 75 HZ) • Supports MARS encryption via interfacing to Station

Manager, V3, and MultiTerm. • Automatic software updates over internet. • Superb Runon protection.

TheModem Features

• Visual feedback for correct Input Audio Level – The Black/Green/Yellow/Red Diamond.

• Uses Harris modem algorithm for calculating Average SNR for choosing best bps.

• No virtual COM ports used.

• Uses 2 TCP/IP sockets. One for Data, and one for remote control & information.

• Provides EOT signal via second socket which Terminal programs (in the future) can use instead of timeout.

• Supports 64 bit Windows 7, 8, 8.1, and 10.

M110A-2700 mode

• TheModem has a second M110A mode called M110A-2700 which is a modified M110A.

• M110A uses 2400 symbols/sec – M110A-2700 was slowed down to 2000 symbols/sec.

• Ideally uses 2700 hz of rx and tx bandwidth.

• Should work decently at 2400 hz bandwidth.

• Compatible with all modern amateur radios.

• Is incompatible with existing M110A hw modems

• I do not expect wide acceptance.

STANAG 4285 mode

• Used in Europe by NATO • I can pick up and decode French transmissions on 6348.0

and 13031.2 USB. Requires not checking “WaitForSOM” “StopAtEOM”, and checking “5N1 ITA2”

• Very similar to M110A, yet has differences. • Uses 2400 symbols per second, so should require identical

TX and RX bandwidth. • My DSP expert says S4285 performs better than M110A

due to repeating preamble and shorter frames. • It appears to me that S4285 and S4529 modes do not

Runon at the receiving station when EOM is missed. • Do all current US Military radio modem include S4285?

TheModem – S4285 selected

STANAG 4529

• S4529 is something I am working on. Also adding a custom auto-baud for the speed/interleave.

• S4529 is 1200 symbols/second. 1200x1.35=1620 HZ bandwidth needed. Spec says 1240 HZ bandwidth.

• Should work with all modern amateur radios.

• User selectable center 800 to 2400 HZ in 100 HZ steps.

• Speeds 75, 150, 300, 600, 1200 bps, Short/Long Interleave. Long=20 seconds; Short=1.7 sec.

• Speed 1800 bps has no FEC (Uncoded) no interleave.

• Do all current US Military radio modem include S4529?

STANAG 4529 – negatives

• M110A Long Interleave 4.8 sec, Short 0.6 sec

• S4285 Long Interleave 10.48 sec, Short 0.853 sec.

• S4529 Long Interleave 20.48 sec, Short 1.706

• Doubling the Interleave duration gives a 2 or 3 dB improvement for fading.

• The frequency offset tolerance is lower for S4529. I have increased max freq offset to +/-375 HZ for M110, S4285, and S4529.

• At any given speed, S4529 has fewer FEC bits compared to S4285, gives 2 or 3 dB SNR reduction.

TheModem – M110, STANAG 4285, STANAG 4529, MT63, and Olivia

• Green diamond audio input volume level

SNR TABLE

•

The Modem FFT graph

TheModem Settings

TheModem Settings - PTT

TheModem Settings -PTT

TheModem Settings - Advanced

TheModem – Automatic Updates

Special One-time version of Station Manager used during TheModem Beta

Testing. Do not use nor distribute.

Configuration timeout M110A 3000, MT63 5000ms, Olivia 7000ms.

Station Manger V2 configuration. No Virtual Com Ports. COM16 not used.

Station Manager V4

Bob Baker’s MultiTerm (AAA6R6)

MultiTerm settings Tab

MultiTerm features

• Simple user interface • Displays decrypted characters as they arrive rather

than after the entire message is received • Terminal and crypto functions • Interfaces to software and commercial modems via

serial or TCP/IP ports • Received and Autosend folders for Message Machine

streams • Built-in help with optional mouse hover tips • Optional chat, checksum validation and Message

Machine commands

V3 – RMI (Radio Modem Interface)

V3 – RMI Settings

V3 - Terminal

Bob Baker’s MultiTerm is impressive

• TheModem can be connected with up to 10 Terminal Programs simultaneously. Sends the same decrypted data to all 10 Terminals.

• In this case Station Manager and MultiTerm had “Checksum Failed”. Station Manager showed garbage, and MultiTerm shows periods for the nonprintable characters after “AAR3GI”.

• MultiTerm provides a separate Message Editor program to help the user construct messages and sends them via Multiterm.

• MultiTerm decrypts as the message arrives without waiting for the end of the message – displaying the message much faster.

• MultiTerm is in use by Army MARS Region 6. • Station Manager has the most features. Mitch Winkle did an

excellent job. • TheModem works with all these Terminal programs.

TheModem BETA testing

• Almost every BETA tester owned a hardware modem and F8101 radio.

• Tested against RapidM and Harris hardware modems.

• Hardware Modem owners were very impressed with TheModem’s performance.

• Passed encrypted traffic via M110A, MT63.

• Olivia was not yet added to TheModem.

TheModem

• Even if DOD purchased every volunteer a hardware modem – or TheModem software… Still the volunteers’ radios are inadequate.

• Will not perform as well as a military radio with modem.

• Nevertheless, TheModem software provides a large M110A communications reliability improvement for MARS and SHARES volunteers.

Army Mars Regional Training Officer:

• “Well, I was in the computer field and did a lot of programming and systems design. I’ve been complaining about MS-DMT from the first time I used it. Aside from it being incredibly unfriendly, it was also crashing or hanging constantly. Also, as the Training Officer, I was all the trouble people had with it. Using virtual COM ports to link the programs was another crazy way of doing things when you could use tcpip like you have done. I’m using your software on my secondary station as I’m using an RM2 modem on my primary MARS station using Datapoint software. I got so sick of DMT that I just bought a hardware modem over a year ago. “

MARS Regional Exercise Coordinator

• “I want to congratulate you on your Modem. I have been able to compare it side by side with MS-DMT, running two programs at once and your modem performs equally well if not better with out crashing than MS-DMT, and using TCP instead of virtual comports is great! I'm going to send for two licenses so I can run it on two different computers.”

Mars Regional Exercise Coordinator Continued

• “First a programmer should get something for all their coding. But the main reason is MS-DMT crashes when you least expect it. Yours doesn't The virtual com ports are a issue at times. No virtual com ports needed. TCP Ports make it easier to run V2 Station Manager and V3 programs at the same time. Like that it switches to same speed received in transmit. Auto updates. Just a few reasons why I believe $xx was worth it.”

From an Army MARS state director:

• “I have a Harris RF MIL-STD Modem and did a side by side comparison between The Modem and Harris RF Modem. Every test from 75 to 2400 The Modem was as clean and compliant as the Harris RF setup ( it actually beat the Harris at 1200 and 2400). The Harris is disciplined to a Rubidium / GPSDO 10 MhZ Frequency Standard along with the Flex 6500 that I use for most of my MARS Operations.”

How to get TheModem

• Free one month trial license for all MARS and SHARES volunteers.

• Paid yearly licenses tied to a single computer. • Will lose license if Windows is reinstalled or hw

changed. • Large discount for Mars/Shares volunteers

installing on their personally owned computers. • Competitive price for Government, Corporations,

NGOs, and paid Mars/Shares members (e.g. Chief Army Mars, Chief Air Force Mars, MARS contractors).

Contact Information

• Everyone should start with a trial license to make sure he/she is fully satisfied before purchasing a yearly license.

• If you want TheModem on two computers, must buy two licenses.

• Email AFA3ZH@gmail.com or NNH3BI@gmail.com for trial license