28 March 2015

analog SSTV

analysis and visual decode of analogic HAM SSTV on 14030.0 KHz USB

27 March 2015


STANAG-4197 is  a NATO standard agreement indicated as "Modulation And Coding Characteristics That Must Be Common To Assure Interoperability Of 2400 Bps Linear Predictive Encoded Digital Speech Transmitted Over Hf Radio Facilities".
A description of the STANAG-4197 waveform can be found in radioscanner.ru, below a self-explanatory picture about the four parts of this signal:   

STANAG-4197 waveform (courtesy radioscanner.ru)
The S-4197 modem generates two separate signal formats based on two tone libraries: the 16-tone library is used for the system preamble and the 39-tone library is used for digital voice data. The initial preamble (modem preamble) is used in the receive modem for the detection of signal present, the correction of doppler, and the identification of the beginning of the system preamble. Modem preamble consists of four unmodulated tones followed by three tones simultaneously phase modulated.   
The modem preamble segment is sent on 16 channels at 75 Baud and channel separation 112.5 Hz (~112),  encoded voice (LPC) segment is sent on 39 channels at 44.44 Baud and channel separation 56 Hz: both the segments are formed using OFDM technology. 

This waveform is used in Advanced Narrowband Digital Voice Terminal (ANDVT or AN/DVT) modems that transmit encrypted digital voice over HF, these modems include the ANDVT MINTERM KY-99A modem. Sometimes you may found this signal under the ANDVT name, but it's wrong since STANAG-4187 is the waveform while ANDVT is the modem.

OFDM 16-tone data segment
OFDM 39-tones voice segment

26 March 2015

CIS-45 v2 HDR modem 40 Bd BPSK

CIS-45 Ch, Russian 45 tones HDR modem, version 2 http://signals.radioscanner.ru/base/signal230/
CIS-45 version 2 shows a reduced CP and manipulation speed increased to 40 Hz so the maximum operating speed is increased to 1800 bps. In general, the signal is the same as CIS-45 HDR modem version 1.

Bandwidth: ~ 3200 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): 40

45 tone and pilot tone (spectrum)

Here is another CIS-45 reception (25 mar) that shows a better signal quality in the upper channels:

25 March 2015

CIS-60 HDR modem 30 Bd, π/4-DQPSK

heard this morning on 14259.0 USB at 0720z, this is the second mode of the so-called "CIS-60" family: a CIS/Russian  OFDM HDR modem 60-tones + 1 pilot. 
Unlike the transmission heard yesterday, and reported in another post, the manipulation speed is 30 Baud per channel and modulation in channels is π/4-DQPSK; the channel separations remains at 44.44 hertz. I just would remember that the CIS-60 first mode is a π/8-DQPSK-8, 35.5 Baud mode.

Bandwidth: ~ 3000 Hz
Number of channels: 60 + 1 pilot tone (~ 3300 Hertz)
Manipulation in the channels: π/4-DQPSK
Step between channels (frequency net/grid): 44.44 Hz
Manipulation speed (Baud rate): 30 

21 March 2015

FSK-CW (or FSK/Morse)

FSK-CW, also known as SFK/Morse, means Frequency Shift Keying CW and is a variant of QRSS (extreme slow speed CW, from Q-code QRS) that instead of activate/deactivate the carrier, the carrier is always activated as long as the transmission lasts. During pauses between dots, dashes or characters the frequency is shifted downwards. Whilst the upper trace shown on the screen contains the Morse information the lower trace is drawn during signal pauses. 
The advantage of this mode is its redundancy. If, for instance, a dash is falling into pieces caused by QRM there's still a chance to determine subsequently by checking the lower trace if the signal really had contained that dash or rather several dots. 

The copies in figures are from Russian Navy.

17 March 2015

MIL STD-188-110 Appendix B, 39-Tones (M-39)

"MIL-STD-188-110 39 Tone is a non-mandatory part of the MIL-STD-188-110 military standard for use by all departments and agencies of the Department of Defense. 
The modulation technique used in this mode consists of differential quadrature phase shift keying (QDPSK) of 39 orthogonal sub carriers in the range from 675Hz to 2812.5 Hz, and an additional unmodulated Doppler reference tone at 393.75Hz. The modulation speed (symbol rate) is always 44.44 baud. Through the transmission of redundant information on certain tones, different user data rates can be achieved within a range of 75 to 2400 bps.
This mode uses FEC and interleaving to combat the effects of fading, frequency shift, multipath, and burst noise.

The user data is transmitted using a continuous frame structure with a variable block length (number of symbols), depending on user data rate and message type. Each transmission starts with a preamble, consisting of three phases, followed by block synchronization and data segments. The data block immediately follows the next block synchronization segment defining again the start of the next data block. This repeated frame structure enables synchronization of the demodulator at any time of transmission.
The end of transmission is determined by an EOM sequence".

Radioscanner.ru reports analysis of the 188-110 App.B waveform at this page: 
although the sample has some problems of digitization (maybe due to PC sound card) and wrong sampling rate. According to http://www.radioscanner.ru/info/article538/ MIL 39-tones has a native sampling of multiple of 3600 hertz so I resampled my recording obtaining the right K = 17/64 along with the expected values for baudrate and channel separation. 

sinosoidal OTH-Radar and Sounder

observed during last days on HF:

15 March 2015

CIS-12: an example of link-setup

heard (or better.. "seen") on 14 March at 10556.0 USB (10558.0 cf) 0740z. I posted the log and a short recording within a short analysis to UDXF list and below the interesting comments  by Trond Jacobsen - Hvaler archipelago, SE Norway (59.0333N 11.0333E JO59MA).

"The initial part of the opchat could have been very short. Most likely they migrated from another frequency and already had agreed on using CIS-12 (QYT4), - and just sendt a "qrv?" and got "qrv" in return. This was then followed up by a "qnj" (can you copy me), the op replies and they set up the crypto link.
Note that some Russian units key the second (in this case the third) tone of the CIS-12 in Morse to send opchat, in preference to using a separate Morse net like the navy does.

 1) the op told the other end of the link that "I copy you well" (QNJ3):

 2) and that they are ready to use "special equipment" (QJB3):

Interesting that they used "qnj" instead of "qrj" (QNJ has a wider range of response (1-5) then QNJ (1-3)) and that they used the additional QJB3 prior to the use of the CIS-12 as CIS-12 in itself is "special equipment" and is arranged used with the qyt4.
Drill or excersise maybe ??

Thanks to Trond for the his interesting commets.

5 March 2015

RTCE Sounders

The key to achieving significant benefits in the way that an operator or automated HF radio system controller uses the propagation medium for communication is to ensure that an adequate supply of  real-time data is available for decision-making purposes. Off-line propagation analysis is the older time-proven method for getting this information. More recently automated and adaptive systems have turned to real-time collection of information to be used in propagation analyses.
Sounding belongs to a general class of channel estimation or evaluation techniques (RTCE real-time-channel evaluation).
Sounding is the process of monitoring or testing the transmission medium for real-time propagation information. Soundings provide up-to-date indications of propagation characteristics over vertical (directly overhead) paths and oblique paths (along the actual communication route direction). It is not practical to sound all possible paths in a large communication network, but some benefits from sounding may still be achieved if selected paths are probed and the results are extrapolated to geographically nearby paths. 

Sounding can be divided into three subgroups for purposes of distinguishing the significance of each type. The subgroups consist of ionospheric pulse sounding, linear sweep sounding, and channel evaluation sounding

Ionospheric pulse sounding
Ionospheric pulse sounding is used to test the propagation medium caracteristics for such things as channel unit impulse response, signal propagation delay, and signal amplitude. Pulse sounding consists of emitting a pulse sweep over a portion or all of the HF band for a period of a few seconds to several minutes. The received signal is then analysed. The results of a frequency sweep of a sounder will indicate to the user, or automatically to the equipment the range of frequencies that will propagate. Vertical-incidence-sounder (VIS) where the soundings are emitted vertically and the reflected returns are received by a nearby receiver and oblique incidence backscatter sounding where the soundings are emitted in the direction of the actual communication, and the returns scattered from a distance are gathered by a co-located receiver very near the transmitter, are general techniques which require interpretation before being of direct use to an adaptive link.
Oblique-incidence-sounder (OIS), where the sounding is emitted in the direction of the actual communications path, and the receiver is located at the remote location, is of more direct application, subject to the antennas and system parameters in use

continuous-sweep sounder leaving a gap between (more ore less) 16170 and 16200 KHz
Linear swept frequency sounding (i.e. chirp sounding)
Linear FM modulation or chirp sounding consists of sending at low power 2-30 MHz. This method can be linear FM/CW test signal over the communication path used over either a vertical or an oblique path. The data received from the chirp sounding equipment is similar to the pulse sounding equipment, but has the advantage of causing less interference to nearby equipment.
Oblique incidence sounding technology offers benefits for adaptive HF communications systems using the 2-30 MHz bands. In addition, the frequency modulated continuous wave (FMCW) swept-frequency “chirp” method is shown to offer adaptive HF system engineers with more options in the design of HF networks. Moreover, it is found that FMCW “chirp” sounding provides the communicator with a relatively unobtrusive waveform for establishing optimum network connectivities, if the sounding is carried out in near-real time and the network consists of frequency-adaptive radio.
Recommendation ITU-R F.1337 outlines the case for frequency management of adaptive HF radio systems and networks using FMCW oblique incidence sounding. Specifically it recommends that automatic and adaptive management schemes beconsidered for adaptive HF networks to include dynamic selection of optimum frequencies, the sharing of frequencies within a network, and adaptive selection of alternate network paths; that FMCW “chirp” sounding be considered for use in dynamic frequency management schemes including:
- as a real-time input data source for updating resource management and propagation prediction programmes;
- as a means for updating the frequency scan lists of adaptive HF systems;
- for modification and enhancement of the link quality analysis (LQA) matrices for adaptive HF systems;
- as a complement to the exclusive use of in-band channel sounding, thereby increasing network communication capacity and reducing interference introduced by channel sounding.
Channel evaluation sounding
Channel evaluation sounding consists of probing only frequencies that are allocated to this system, rather than a broadband approach of the other two methods. Channel evaluation provides information used in evaluation of signal-to-noise performance such as: data error rate, speech intelligibility, and noise levels.

Something about sounder-tech products may be looked at here:
but, as usual, Google is your friend...

Below a single-sweep sounder, up-chirped, observed around 18 Mhz (you may observe these sweeps several times in just one hour or so):

FHSS, Frequency-Hopping spread Spectrum

Frequency-hopping Spread Spectrum (FHSS) is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver.

The spread-spectrum transmission offers three main advantages over a fixed-frequency transmission:

    1) Spread-spectrum signals are highly resistant to narrowband interference. The process of re-collecting a spread signal spreads out the interfering signal, causing it to recede into the background.

    2) Spread-spectrum signals are difficult to intercept. A spread-spectrum signal may simply appear as an increase in the background noise to a narrowband receiver. An eavesdropper may have difficulty intercepting a transmission in real time if the pseudorandom sequence is not known.

    3) Spread-spectrum transmissions can share a frequency band with many types of conventional transmissions with minimal interference. The spread-spectrum signals add minimal noise to the narrow-frequency communications, and vice versa. As a result, bandwidth can be used more efficiently.

Spread-spectrum signals are highly resistant to deliberate jamming, unless the adversary has knowledge of the spreading characteristics. Military radios use cryptographic techniques to generate the channel sequence under the control of a secret Transmission Security Key (TRANSEC) that the sender and receiver share in advance.

4 March 2015

just another HF sounder

10984.0 HF sounder, mode: FMCW, bw: 3300 Hz (less ore more), sweep-rate: 4 sps up-chirped

1 March 2015

OTH radar: sweep-rate switching

This is the same OTH radar, maybe the UK PLUTO from Cyprus, heard in two conscutive times: as you may see it changes its sweep-rate according to the needed range and target.

running at 25 sweeps/sec

now running at 50 sweeps/sec