CIS MFSK-64 (32+32) 45Bd

I recently had the chance to have a good copy of MFSK-n signal previously reported here as a MFSK 68-tone (34+34). Well, according to my new measurements, I tend to reconsider it as a parallel 64-tone (32+32) signal: this way the shift of 46.9 Hz among the tones is closer or almost the same of  the apparent speed of 47 symbols/sec. 

PSK-8 9000Bd bursts (2 symbol element periods length) are sent each 1 second, possibly acting as sync (Fig. 1):  since the embedded PSK inserts, the signal occupies a bandwidth up to ~10KHz.

Fig. 1

It's worth noting that in the first half of the transfer a 3-tone symbols alphabet is used, while a 5-tone symbols alphabet (the most frequent in this wavefrom) is used in the second half, from time t1 (Fig. 2). In both the cases the speed of 45 symbols/sec remains constant (Fig. 3)

Fig. 2

Fig. 3

The measured 47 symbols/sec from SA likely results from the add of the two symbols due to the PSK-8 inserts.
The 64-tone solution can be easily seen by counting the tones over the -40dB threshold in the upper and lower part of the signal plotted in the FFT spectrum /Fig. 4).

Fig. 4

The number of the used tones remains constant, as well as the speed, for both the two alphabets (Figs 5,6) although the count of the grid in the second half of the signal (5-tones symbols) is more difficult.

Fig. 5

Fig. 6

Often you can see the CIS-3000 PSK-8 3000Bd modem before MFSK-64 as in Fig. 7: it's interesting to note that CIS-3000 and PSK-8 inserts have the same sub-carrier value (~5300 Hz) and it just matches the center of the MFSK-64 FFT spectrum (Fig. 8)

Fig. 7

Fig. 8

MFSK-64 is likely a Russian Intel parallel tones system as well as other MFSK and CIS-3000 could be employed as a sort of selcall. 

https://yadi.sk/d/WMnwnpN034qLZV 

we do not remember the days but the moments. Merry Christmas.

ICAO METARs TAFs sent over MIL 188-141 2G-ALE

This MIL 188-141 2G-ALE session  has been copied today 23 Dec. on 09019.0 KHz/USB starting from 1010 UTC. The ALE addresses are:  XSS, RAF base in Forest Moor UK belonging to DHFCS-net (Defense High Frequency Communication Service) and UKE304, RAF E3D AWACS Aircraft: respectively TAZ and NATO35 callsigns. The Comms  are conveyed by AMD commands which are embedded in 188-141. After the handshake, this is the first message sent by the Awacs, requesting METARs and TAFs (weather informations) for some airports in Cyprus identified by LCRA LCLK, and  LCPH:

LCRA - AKROTIRI 
LCLK - LARNACA/LARNAX 

LCPH - PAPHOS/BAF

TAZ DE NATO35 HELLO WE R RQSTING METARS N TAFS FP LCRA LCLK LCPH TVM

followed by the reply from ground:

DE TAZ WAIT ONE

something like "wait a moment..." then the requested weather informations for LCRA, LCLK, and LCPH are sent by TAZ (XSS)

LCRA 230850Z 14003KT 9999 6000E -SHRA SCT022CB BKN045 13/10 Q1019 BECMG 9999 FEW022CB

TAF LCRA 230732Z 2309/2403 09005KT 9999 BKN050 PROB 303

TEMPO 2309/2403 5000 TSRA SCT022CB

LCLK 230930Z 08007KT 9999 FEW020TCU 15/11 Q1020 NOSIG

TAF LCLK 230530Z 2306/2406 04008KT 9999 SCT020 BKN040 PROB40

TEMPO 2306/2406 5000 SHRA PROB330

TEMPO 2306/2406 VRB20G30KT 2000 TSRA SCT020CB

BECMG 2309/2312 21010KT

BECMG 2316/2319 33007KT

LCPH 230930Z 07006KT 9999 FEW0bkX30TCU SCT050 15/09 Q1019

TAF LCPH 230530Z 2306/2406 07008KT 9999 SCT020 BKN040 PROB40

TEMPO 2306/22406 5000 SHRAPROB30

TEMPO 2306/2406 VRB20G30KT 2000 TSRA SCT020CB

BECMG 2308/2311 24010KT

BECMG 2316/2319 03007KT

Transmission is terminated by:

THATS THE WX COMPLETED K

METAR (METeorological Air Report) is a format for reporting weather information which is predominantly used by pilots in fulfillment of a part of a pre-flight weather briefing, and by meteorologists, who use aggregated METAR information to assist in weather forecasting. METAR is a common format and highly standardized through the International Civil Aviation Organization (ICAO) which allows it to be understood throughout most of the world.
A typical METAR contains data for the temperature, dew point, wind speed and direction, precipitation, cloud cover and heights, visibility, and barometric pressure. A METAR may also contain information on precipitation amounts, lightning, and other information that would be of interest to pilots or meteorologists such as a pilot report or PIREP, colour states and runway visual range (RVR). TAF (Terminal Aerodrome Forecast) complement and use similar encoding to METAR reports.
TAFs are produced by a human forecaster based on the ground. For this reason there are considerably fewer TAF locations than there are airports for which METARs are available. (quoted from Wikipedia)

PSTN V-series modem over a radio link ?

This transmission has been copied on 6421.5 KHz/USB at 0808 UTC and consits of five parts:

1) initial FSK 300Bd call and link negotiation, between the calling and the answering modem;

2) PSK 1200Bd data transfer from the calling modem;

3) FSK 300Bd from the answering modem (a mode switch request ?);

4) PSK 600Bd data transfer from the calling modem;

5) FSK 300bd likely as ACK and link disconnect;

Each FSK/PSK frame is preceeded by a 1500Hz short tone (Fig. 1) and looking at the strength of the PSK frames they seem to be sent by the calling modem.

Fig. 1

The FSK signal initialing the link has a speed of 300Bd and shift of ~170Hz (Fig. 2). Once demodulated,  it exhibits a 10-bit length period and matches the 8N1 format: one start bit, one stop bit, no parity and 8 data bits (Fig. 3).

 

Fig. 2

Fig. 3

Speeds, carriers and PSK constellations related to the PSK frames are shown below in Figs 4,5 (note the amplitude failure in the initial 1200Bd PSK frame that impairs its study):

Fig. 4

Fig. 5

It's interesting to note that the waveforms of the PSK frames match some of the ITU-T V series recommendations for data communication modems over the Public Switched Telephone Network (PSTN):

1200 Baud, 1800 Hz carrier, PSK-4 (2400 bps gross) --> ITU-T V.26

 600 Baud,  1200 Hz carrier, PSK-4 (1200 bps gross) --> ITU-T V.22 (Bell 212A)

(ITU-T recommendations can be read here)

My friend KarapuZ, who pointed me to ITU modems, heard some other V-serie modem on HF: maybe some tests or arrangements as proof-of-practice about the feasibility of such unusual solution (PSTN modem over HF). It's worth noting what seems to be a sort of adaptive solution, the 1200-600 Baud switch, and that the military often use such modems but on VHF repeaters.

Comments are welcome.

https://yadi.sk/d/bLw66QsT33w5Cv 

HARRIS proprietary Autolink-I (1G-ALE)

Very interesting ALE session consisting of HARRIS Autolink-I handshake (a proprietary waveform) followed by a data transfer using MIL 188-110 App.B 39-tone OFDM modem (M39) and link disconnect: since the used technology, 1G-ALE and 39-tone, the session is almost a sort of HF flashback. The transmission has been heard on 12567.0 KHz/USB at 1140 UTC 13 December, most likely from Moroccan Military.

The Harris Autolink-I system was one of the first adatptive and automated HF systems available and was implemented in the Harris RF-7110 controller, then it was upgraded to a RF-7210A Mil Spec Autolink-II. The basic difference between the first and second generation units is in the type of utilized addressing:  call signs in the 1G controllers are limited to numerical digits while 2G controllers can employ up to 15 alphanumerical identifiers.

Fig. 1

Autolink-I employs an FSK waveform modulated at 200 Baud and shift of 200 Hz (Fig. 2). Structure is very similar to Harris RF-3560 Selcall. Preamble is a sequence of reversals and its duration is proportional to the number of channels in use so receivers have a chance to lock on the signal while scanning. Then, info is about 800 ms. and consists of some control words and 4 digits numeric call sign (Fig. 3). In case of group call to test channel conditions, answers are slotted.

Fig. 2

Fig. 3

As said, the data transfer is achieved with MIL 188-110 App.B, a 39-tone OFDM waveform introduced with the first release of 188-110 Standard and not recommended for new systems by the 3rd release (188-110C, September 2011). The modulator output consists of 39 QDPSK data tones which have a constant modulation rate of 44.44 Bd for all standard input data signaling rates from 75 to 2400 bps, plus an unmodulated tone for Doppler correction (Fig. 4).

Fig. 4

 https://yadi.sk/d/ktH1ujcc33R6s4

 https://yadi.sk/d/SPOJ9-x_33R6yv