26 April 2015

RTTY BAUDOT 50/450


The original (or "Baudot") radioteletype system is based almost invariably on the Baudot code or ITA-2 5 bit alphabet. The link is based on character asynchronous transmission with 1 start bit and 1, 1.5 or 2 stop bits. Transmitter modulation is normally FSK (F1B). Occasionally, an AFSK signal modulating an RF carrier (A2B, F2B) is used on VHF or UHF frequencies. Standard transmission speeds are 45.45, 50, 75, 100, 150 and 300 baud.
The word Teletype was a trademark of the Teletype Corporation, so the terms "TTY", "RTTY","RATT" and "teleprinter" are usually used to describe a generic device without reference to a particular manufacturer.

Common carrier shifts are 85 Hz (used on LF and VLF frequencies), 170 Hz, 425 Hz, 450 Hz and 850 Hz, although some stations use non-standard shifts. There are variations of the standard Baudot alphabet to cover languages written in Cyrillic, Arabic, Greek etc., using special techniques.


The correct measurement of the baudrate can't be done with the usual methods (ADP or quadrature AM detector) since we obtain a wrong value; as usual, the confirm comes from the raster-scan method. 

wrong manipulation speed from ADP
RTTY is an start-stop transmission (async), and the period is 1.5 stop bits: this is clearly visible  in the scan raster

manipulation speed from the raster

Given the FSK mode we have only two symbols, so baudrate (symbol per second) is equal to the speed in bps (bit per second). Some combinations of speed and shift are standardized for specific services using the original radioteletype system, see:

23 April 2015

Logs: 17-21 April

09089.0 RA8: Polish Mil, POL 0627 MIL 188-141A clg TA7 (17Apr15) (AAI)
09089.0 RA8: Polish Mil, POL 0631 MIL 188-141A clg AS9 (17Apr15) (AAI)
09089.0 RA8: Polish Mil, POL 0634 MIL 188-141A clg MU9 (17Apr15) (AAI)
09089.0 WO4: Polish Mil, POL 0646 MIL 188-141A clg RA8 (17Apr15) (AAI)
09089.0 DY1: Polish Mil, POL 0703 MIL 188-141A clg RA8 (17Apr15) (AAI)
09089.0 AS9: Polish Mil, POL 0706 MIL 188-141A clg RA8 (17Apr15) (AAI)
11032.0 ---: Russian Mil, RUS 0630 CIS-45 OFDM 45-tone (20Apr15) (AAI)
11181.0 CROSPR: USAF Croughton, G 0707 MIL 188-141A clg MOBD01DAT unid aircraft (20Apr15) (AAI)
12129.5 ---: unid (prob. Russian Mil) 0635 FSK 100Bd/2000 (15Apr15) (AAI)
11213.0 MKL: RAF Northwood, G 0907 STANAG-4481 75Bd/850 KG-84C messages (16Apr15) (AAI)
11228.0 ---: unid NATO stn 0840 MIL 188-110A KG-84C messages (16Apr15) (AAI)
12874.0 ---: Unid 0650 CW strings of "VVV" (21Apr15) (AAI)14421.0 CNC: Algerian AF, ALG 0808 MIL 188-141A clg CM3 (19Apr15) (AAI)
16175.0 ---: Russian Mil, RUS 0805 CIS 3x100, VFT 3 channel FSK 100Bd/1400 (16Apr15) (AAI)
16553.5 ---: Japanese Military, J 1840 4 FSK-2 channels 300 Hz shift, 100 Bd (20Apr15) (AAI)
23169.5 ---: unid 1140 2400 Bd serial-tone PSK-8, burst mode (20Apr15) (AAI) [1]
23337.0 JDG: DGA USAF Diego Garcia, DGI 1135 MIL 188-141A sndg (21Apr15) (AAI)
24153.0 D54: Chinese Mil, CHN 1153 MIL 188-141A clg N50 (20Apr15) (AAI)


interesting waveform here:
[1] Acrotel MAHRS 2400 EADS/RACOMS serial  

Arcotel MAHRS-2400 ALE burst (Telefunken Racoms)




Fast bursts sent every 500 msec, spreading about a 2800 Hz bandwidth. Each burst shows a short preamble of 8 un-modulated carriers, symmetrical with respect to the center frequency of the signal, and a short PSK-2 preamble. The data segment is a serial tone carrier at ~ 1800 Hz with a PSK-8 manipulation at 2400 baud.

http://signals.radioscanner.ru/base/signal58/ 

The MAHRS protocol, or better the procedure, was described in WUN-10 newsletter, and here reported:
"For establishing the link between two stations there is a call of one dot each second at a length of 500ms. Most of the time the station calls 62 times then changes back to listening for 60 seconds and then selects a new frequency for calling. The selection of freqs happens according to position of both sender and receiver, actual daytime and actual sunspot numbers. The system calculates a prediction model of propagation and decides which line may be the best. When in contact the called station answers after waiting a maximum of 15 seconds by one dot of 500ms and the both stations give their "handshakes" and then the full transmission starts using a high speed ARQ like transmission system at a speed of 4800 bps" [http://www.udxf.nl/WUN-v10.pdf]

Sometimes you find the MAHRS protocol reported along with the names EADS/RADCOM and Arcotel: the former is the name of the HW producer, TELEFUNKEN Radio Communication Systems - TELEFUNKEN RACOMS (http://www.army-guide.com/eng/firm3787.html) while the latter (Arcotel) is the name of the modem (now indicating the radio processor).
The source should be the German Mil, as reported in the above link to WUN newsletter http://www.udxf.nl/WUN-v10.pdf


21 April 2015

Japanese Military 8 frequencies: 2 FSK channels, cross-schema reduntant

This signal was seen on 16553.5 KHz/USB around 1900z  and - at that same time - on 12384.5 KHz/USB by my friend Mauro IK2GFT from Milano:


It is composed of 8 distinct channels, 300 Hz spaced and 100 Baud as symbol rate. The signal uses about a 2400 Hz bandwidth.
The signal consists of two independent FSK-2 channels which are doubled according to a cross-schema (tones separation too is doubled), so the 4 FSK-2 channels (8 traces) that are visible in the sonogram/spectrum. According to the analysis performed by radioscanner group, all the four channels use the Manchester code and, since the time offset between the first and second channel, they are formed using OFDM technology.

more info here (signals.radioscanner.ru) 



14 April 2015

SITOR-ARQ (SITOR-A)




SITOR-ARQ is a simplex/duplex FSK 100Bd/170 system where both stations transmit alternatel. The CCIR recommendation 476-3 defines a cycle of 450 ms and the two stations are designated as follows:

ISS: information sending station
IRS: information receiving station

The SITOR 7 bit alphabet employs a 3:4 mark-space ratio. The ISS transmits blocks of 210 ms duration each containing 21 bits. In turn the IRS transmits acknowledgement bursts with a duration of 70 ms. If the ISS does not receive an acknowledgement, a block containing the RQ character is sent. In the case of blocks being received in error by the IRS, the last data block sent is repeated.

13 April 2015

Logs: 09-13 Apr

08850.0 H12: unid US Army, KSV 1300 MIL 188-141A clg TSCP (10Apr15) (AAI)
09038.0 TSCP: US Army Aviation Camp Bondsteel, KSV 0724 MIL 188-141A sndg (08Apr15) (AAI)
09125.8 ---: unid NATO 0730 USB STANAG-4197 1800bps crypto (08Apr15) (AAI)
09163.0 ---: X06 Russian Diplo/Intel, RUS 1735 MFSK 6-tone (mazielka) selcall sequence "145632" off 1740 (12Apr15) (AAI)
09219.0 BB3: Israeli Air Force, ISR 2132 MIL 188-141A sndg (09Apr15) (AAI)
09243.0 ---: Russian Intel 1940 CIS MFSK-20 10Bd (09Apr15) (AAI)
09274.0 DD3: Israeli Air Force, ISR 1540 MIL 188-141A sndg (12Apr15) (AAI)
10170.0 A04: Polish Mil, POL 0616 MIL 188-141A clg HARPIA81 (13Apr15) (AAI)
10170.0 HARPIA81: Polish Mil, POL 0614 MIL 188-141A clg AMANIAN04 (13Apr15) (AAI) [1]
10170.0 HARPIA81: Polish Mil, POL 0616 MIL 188-141A clg A04 (13Apr15) (AAI)
10170.0 HARPIA81: Polish Mil, POL 0619 MIL 188-141A clg SR117 (13Apr15) (AAI)
10170.0 ---: [not copied] Polish Mil, POL 0702 MIL 188-141A clg PASKAL (13Apr15) (AAI)
10170.0 P90: Polish Mil, POL 0638 MIL 188-141A clg SR117 (13Apr15) (AAI)
10820.0 99910: MFA Cairo, EGY 1931 CODAN Chirp SELCALL to 11107 Egyptian embassy London (09Apr15) (AAI)
11018.2 ---: Russian Mil, RUS 0635 OFDM 128-tone modem 21Bd/23.5 QAM-4 (08Apr15) (AAI)
11032.0 ---: Russian Mil, RUS 0645 OFDM 45-tone modem 40Bd/62.5 (10Apr15) (AAI)
11106.0 EK9: Greek Military, GRC 1709 MIL 188-141A clg-Tis GEF + voice + clg-Tws (12Apr15) (AAI)
11555.5 HBZ: unid asset/network 0705 MIL 188-141A clg HFC then into MIL 188-110A crypto msgs (10Apr15) (AAI)
13850.0 ---: unid 0610 PACTOR-III "$z$ saeahafeisakajafal" + crypto text (10Apr15) (AAI)
14550.0 X24: Moroccan Military, MRC 0626 MIL 188-141A sndg (08Apr15) (AAI)
16256.5 ---: unid 1240 Système 3000 robust MFSK-8 (12Apr15) (AAI)
16368.2 ---: unid NATO 1235 STANAG-4285/600bps/L encrypted (08Apr15) (AAI)
17435.0 ---: M42 Russian Diplo/Intel, RUS 0735 SERDOLIK (CROWD-36) MFSK 34-tone (08Apr15) (AAI)
18177.0 ---: X06 Russian Diplo/Intel, RUS 0758 MFSK 6-tone (mazielka) selcall sequence "164253" (08Apr15) (AAI)
22548.2 ---: unid NATO stn 1025 STANG-4285/2400L crypto (12Apr15) (AAI) 


10 April 2015

HFDL/ARINC-635


HF Data Link (HFDL) protocols are defined in the ARINC (Aeronautical Radio, Inc.) Specification 635-3, published on December 29, 2000. The development of HF Data Link service builds on the experiences of ACARS (Aircraft Communications Addressing and Reporting System), therefore HFDL is also known as HF-ACARS.
HF Data Link employs M-ary Phase Shift Keying (M-PSK) to modulate a carrier centered at RF+1440 Hz, where RF is the nominal HF carrier frequency and the characteristic single tone pre-key. The carrier is modulated with 1800 symbols per second (Baud). ACF value is 25 mSec.

ACF value
HFDL frame

Although the 1800 Bd speed, the rate at which user data is transmitted can be selected to be 300, 600, 1200 or 1800 bps. 
1800 Bd - BPSK

1800 Bd - QPSK

300 bps user data rate


9 April 2015

SERDOLIK OFDM 61-tone

the signal shows an OFDM part followed by the usual Serdolik MFSK-34: this is one of the several variants of the Russian system SERDOLIK.


As the 35-tone OFDM mode, this variant shows a 40-samples lenght for LG, 35 tones and spreads a about 3000 Hz bandwidth.
This mode has an easily distinguishable pilot tone at the lower channel so the used channels count to 60 and they are PSK-4 manipulated at 40 Hz (aggregate speed 2400 bps). Separation among channels is 50 Hz, since the presence of CP. The other parameters of the correlation triangle are Br-40, Sh-50 and 'magic K' = 1/4.



7 April 2015

short log

08984.0 ND01: Algerian Mil, ALG 0942 MIL 188-141A clg AC01 then into MIL 188-110B OFDM 39-tone/PSK-4 (06Apr15) (AAI)
08984.0 AC01: Algerian Mil, ALG 0945 MIL 188-141A clg XV01 (06Apr15) (AAI)
08984.0 QX01: Algerian Mil, ALG 0947 MIL 188-141A clg XV01 then into MIL 188-110B OFDM 39-tone/PSK-4 (06Apr15) (AAI)
14401.5 ---: Czech embassy in Baghdad, IRQ 0630 PacTOR-III, email subject "connection check" (07Apr15) (AAI) 

14468.0 DJT: Algerian AF Djanet, ALG 0742 MIL 188-141A clg CM4 (07Apr15) (AAI)
14538.0 KO1: Polish Mil, POL 0655 MIL 188-141A clg ME3 then into MIL 188-110A 2400bps (07Apr15) (AAI)


Czech embassy in Baghdad, PacTOR-III

6 April 2015

listening to ACARS in HF (HFDL, Arinc-635)

Ground Station #6 Hat Yai in Thailand (Longitude 100.23.24 E, Latitude 6.56.23  N) working the flight UAE383 over Eastern India, both listened on 13270.0 kHz / USB.
Down in the screenshot, notice the squitters received from the Ground Station.


Below, flight VJ0647, over Vietnam, and flight GA0650, over Sulawesi (between Borneo and the Moluccas), both in traffic with the Ground Station in San Francisco (US). In these two cases, not having received squitters, I heard only aircrafts (freq. 13276.0 KHz/USB).



Notice that Sulawesi is about 11600 Km from my antenna.




Chinese Air Defense


China People's Liberation Army  PLA - PLA Air Force / Air Defense 

The Chinese PLAAF net use a huge amount of IDs/stations and frequencies. The fact that plain Chinese voice traffic was heard with typical aero noise background was heard, and the transmissions in voice after ALE call - ups helped identifying this large net. But none of the information is officially confirmed.
Below a short log of ALE calls and 188-110A traffic heard yesterday on 14380.0 KHz (one of their numerous frequencies): all transmissions heard are in USB: MIL 188-141A, MIL 188-110A serial tone 2400/bps.

14380.0 123: 1629 MIL 188-141A clg 112 then into MIL 188-110A 2400bps (05Apr15) (AAI)
14380.0 126: 1630 MIL 188-141A clg 111 then into MIL 188-110A 2400bps (05Apr15) (AAI)
14380.0 125: 1647 MIL 188-141A clg 123 (05Apr15) (AAI)
14380.0 111: 1649 MIL 188-141A clg 126 (05Apr15) (AAI)
14380.0 120: 1703 MIL 188-141A clg 123 (05Apr15) (AAI)
14380.0 122: 1722 MIL 188-141A clg 111 (05Apr15) (AAI)
14380.0 115: 1737 MIL 188-141A clg 111 (05Apr15) (AAI)
14380.0 130: 1747 MIL 188-141A clg 123 (05Apr15) (AAI)
14380.0 217: 1753 MIL 188-141A clg 128 then into MIL 188-110A 2400bps (05Apr15) (AAI)


more about PLA:

http://en.wikipedia.org/wiki/People%27s_Liberation_Army_Air_Force 


4 April 2015

Logs: 31 Mar - 03 Apr

data
08968.0 ---:
USAF HFGCS SIPRNET-GW 0745 MIL 188-110A 1200/Short encrypted messages (01Apr15) (AAI)
11476.5 ---:
Czech embassy Moscow, RUS 0635 PacTOR-III encrypted message "$pa $x$B $Y" (01Apr15) (AAI)
12857.0 6WW: French Navy Dakar, SEN 1855 STANAG-4285 600L (calling ?) "FS DE 6WW IMI KKKKKKKKKKKK" (31Mar15) (AAI) 
15622.2 ---: Russian Mil, RUS 1335 CIS-128, 128-tone PSK-8 OFDM modem 20.9Br/23.46 (03Apr15) (AAI) 
15812.0 ---: Russian Mil, RUS 0705 CIS-45, 45-tones PSK-2 OFDM modem v1 33.33Bd/62.5 bursts (01Apr15) (AAI)
18046.8 ---: MFA Cairo, EGY 1205 ARQ/SiTOR-A message to Islamabad Embassy (31Mar15) (AAI)

ALE
08759.0 AB1: Navy Malta patrol boat P21, MLT 0558 MIL 188-141A sndg-Twas (02Apr15) (AAI)
09073.0 5CIN2D:
French Navy (OMAR HF NG) 0730 MIL 188-141A clg-Tis 5CIN1D (03Apr15) (AAI)
09073.0 5CI:
French Navy (OMAR HF NG) 0728 MIL 188-141A clg-Tis 5CIN1D then into MIL 188-110A (03Apr15) (AAI)
09200.0 13081: Moroccan Civil Protection, MRC 0620 MIL 188-141A sndg-Tws (01Apr15) (AAI)
09234.0 GW01: Algerian Mil, ALG 2035 MIL 188-141A LQA REQUEST RESPONSE to PY01 (01Apr15) (AAI)
09240.0 3341: Turkish Civil Defence Istanbul, TUR 0629 MIL 188-141A sndg-Tws (01Apr15) (AAI)
09300.0 SNB813: Polish Military, POL 0623 MIL 188-141A LQA REQUEST RESPONSE to SPT424 (01Apr15) (AAI)
09300.0 SPT424: Polish Military, POL 0623 MIL 188-141A LQA REQUEST RESPONSE to SNB813 (01Apr15) (AAI)
14406.0 CENTR3: MFA Bucharest, ROU 1221 MIL 188-141A clg-Tis FOL then into MIL 188-110A (01Apr15) (AAI)
14430.0 CM6: Algerian AF, ALG 0647 MIL 188-141A LQA REQUEST RESPONSE to HE2 (01Apr15) (AAI) 
14550.0 JP1: Moroccan Military, MRC 1243 MIL-188-41A clg-Tis G2 then into MIL 188-110A (03Apr15) (AAI)
14550.0 JP1: Moroccan Military, MRC 1245 MIL-188-41A clg-Tws O5 (03Apr15) (AAI)
15708.0 CAOFEM001: FEMA San Juan, PTR 0657 MIL-188-41A sndg (01Apr15) (AAI)
15880.0 CM2: Algerian AF Oran, ALG 0710 MIL 188-141A LQA REQUEST RESPONSE to COF (01Apr15) (AAI)


1 April 2015

CIS-45 v1 HDR modem 33.33 Bd BPSK bursts


CIS-45 Ch, Russian 45 tones HDR modem, version 1 http://signals.radioscanner.ru/base/signal46/
This is a Russian 45 tones HDR modem, version 1, formed using the principles of OFDM and here running in burst-mode. Most likely it is a lightweight version of the Russian 93 tone modem. The HDR name is just an abbreviation of High Data Rate.
The transmission heard on 15812.0 KHz USB at 0705z, is composed of two bursts, sent at irregular intervals. Looking at its features it corresponds to the version 1 of the well known Russian 45-tones PSK-2 OFDM modem (also known as CIS-45), here running in burst mode at 33.33 Baud.
The pilot tone also acts as a sync tone at the beginning of each burst. The 45 sub-carriers in the trailer are un-modulated and followed by a PSK-2 modulated segmen. The data-block after the preamble shows a PSK-2 modulation in the channels at the speed of  33.33 baud.

Bandwidth: ~ 3000 Hz
Number of channels: 45 + 1 pilot tone (~ 3350 Hertz)
Manipulation in the channels: 2-PSK
Step between channels (frequency net/grid): 62.5 Hz
Manipulation speed (Baud rate): 33.33(aggregate 1800)




THALES TRC-1752 Stanag-4285 FEC


I had this signal on 31 Mar on 12857.0 USB around 1850z. My analysis matches the one by radioscanner.ru shown here:
http://signals.radioscanner.ru/base/signal101/

THALES TRC-1752 STANAG 4285 FEC has all the characteristics inherent STANAG-4285 (serial tone carrier 1800 Hz, speed 2400 baud and modulation PSK-8) except for the phase constellation of the preamble.THALES TRC-1752 uses a 'special' preamble with 5-ary constellation maybe for receivers tuning purposes.

 

I had a bit of luck to (clearly) listen and take the preamble of such transmissions: here the preamble is very short, anyway we can appreciate the 5-ary


Thanks to KarapuZ and ANgazu for their help and comments.
TRC-1752 modem seems to be replaced by the HF Multi Mode modem TRC 177X family.