31 March 2015

Logs: 28 - 31 (this morning) March

09904.0 ---: unid NATO stn 0725 NATO-75 75Bd/850 messages (29Mar15) (AAI)
10595.0 RKD48: Russian Mil, RUS 0740 F1B 100Bd/500 encrypted (30Mar15) (AAI)
10796.0 RAA: Russian Navy HQ, RUS 0805 CW "VVV RIT RIT RIT DE RAA RAA QSA? K" (30Mar15) (AAI)
13376.0 ---: Russian Diplo/Intel, RUS 0840 Serdolik, MFSK 34-tones 40Bd/40Sh (29Mar15) (AAI)
13394.0 CM1: Algerian AF Blida, ALG 0827 MIL 188-141A LQA REQUEST RESPONSE to CTF (29Mar15) (AAI)
13400.0 HE2: unid asset/network 0652 MIL 188-141A LQA REQUEST RESPONSE to ING (28Mar15) (AAI)
13850.0 ---: North Korean Diplo, KRE 0655 LSB ARQ/FSK 600Bd/600 (31Mar15) (AAI)
14350.0 ---: unid 0705 OFDM 72-tone 30Bd/37.5Sh burst modem, PSK-4 and PSK-8 in channels (31Mar15) (AAI)
14380.0 ---: (not heard, possibly Chinese Air Defense, CHN) 0745 MIL 188-141A clg 215 (29Mar15) (AAI)
14380.0 ---: (not heard, possibly Chinese Air Defense, CHN) 0752 MIL 188-141A clg 228 (29Mar15) (AAI)
14390.0 ---: Russian Mil, RUS 0820 USB CIS-112, OFDM 112-tone modem DQPSK 22.22Br/25.6Sh (30Mar15) (AAI) 
14451.0 CM2OR2: Algerian AF Oran, ALG 0816 MIL 188-141A LQA REQUEST RESPONSE to ESC (29Mar15) (AAI)
14590.0 ---: unid 1430
MAHRS 2400 EADS/RACOMS burst modem (29Mar15) (AAI)
14780.0 ---: Russian Mil, RUS 1330 F1B 53.8BD/500 idling (30Mar15) (AAI)
14828.5 ---: unid 2212 OFDM 72-tone 30Bd/37.5Sh burst modem, PSK-4 and PSK-8 in channels (28Mar15) (AAI)
14830.0 ---: Russian Mil, RUS 1240 F1B 44.6BD/500 idling (30Mar15) (AAI)

28 March 2015

analog SSTV

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

27 March 2015

Logs: 25-27 March

08706.5 ---: unid NATO stn 0740 USB STANAG-4197 OFDM 39-tones 44.44Bd/56.3Sh PSK-4 (27Mar15) (AAI)
12192.0 VQ7: Polish MIL "VQx-Net", POL 0742 USB MIL 188-141A LQA REQUEST RESPONSE to VQ1 (25Mar15) (AAI)
12192.0 VQ3: Polish MIL "VQx-Net", POL 0743 USB MIL 188-141A LQA REQUEST RESPONSE to VQ1 (25Mar15) (AAI)
12201.0 ---: Russian Mil, RUS 1335 CIS-12, MPSK 12-tones PSK-2 120Bd/200 (26Mar15) (AAI)
14259.0 ---: CIS/Russian MIL 0715 "CIS-60" OFDM 60-tones HDR modem QPSK 30Bd/44.44 (25Mar15) (AAI)
14380.0 3232: unid asset/network 0645 USB MIL 188-141A LQA REQUEST RESPONSE to 129 (27Mar15) (AAI) (*)
14575.0 333: Enigma E11 0745 USB J3E 333/32 (26Mar15) (AAI)

(*) possibly Chinese Air Force network


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)
Data segment is sent on 16 channels at 75 Baud and channel separation 112.5 Hz (~112) while; voice segment is sent on 39 channels at 44.44 Baud and channel separation 56 Hz: both formed with 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 

24 March 2015

Logs: 23-24 March

08154.6 ---: unid 0758 USB F1B 250Bd/170 (possible Siemens CHP-200 modem) (23Mar15) (AAI) 08190.0 PAOLINI: GdF patrol boat, I 1511 USB proprietary PSK 2400Bd bursts + MIL 188-141A clg-Twas CAGLIARI (23Mar15) (AAI) 
08190.0 CINI: GdF training vessel, I 1531 USB MIL 188-141A clg-Tis GENOVA (23Mar15) (AAI)
09240.0 3500143: Turkish Civil Defense, TUR 2059 USB MIL 188-141A sndg; others soundings 312018,363018,376013  (23Mar15) (AAI)
14468.0 BSK: ALG Algerian Air Force Biskra, ALG 0814 USB MIL 188-141A Link Quality Response to CM4 (24Mar15) (AAI)
14557.0 ---: unid CIS/Russian Mil 0750 CIS-60, OFDM 60-tones pi/8 DPSK-8 HDR modem 35.5Br/44.44 + voice chat (24Mar15) (AAI)
15870.0 ---: CIS/Russian Mil 0825 USB FSK 53.8Bd/500 ACF 2bit idling (24Mar15) (AAI) 

Here the misuration of the features (FSK 53.8Bd/500 ACF 2bit) related to the signal heard on 15870.0 Khz USB:

Below, the two interesting signals heard on 8190.0 Khz and 8154.6 Khz, both on USB:

GdF proprietary PSK 2400Bd modem

unid, possible Siemens CHP-200 modem

22 March 2015

Logs: 19-22 March

03756.6 ---: S30 "The Pip" 2150 USB (cf) "pips" markers (20Mar15) (AAI)
04618.0 BPLEZS: Bundespolizei Cuxhaven, D 2036 MIL 188-141A clg-Tis BP25 (19Mar15) (AAI)
05684.0 ICZNPR: HF-GCS Sigonella, I 2017 MIL 188-141A clg-Tis DL0001DAT USAF AWACS Boeing (20Mar15) (AAI)
08566.8 ---: unid 1930 F1B 50Bd/850 ACF 21 bit (22Mar15) (AAI)
09068.0 ---: Russian Mil, RUS 0654 T600/BEE 50Bd/200 Message Sync 0x1414bebe952 (20Mar15) (AAI)
10309.0 ---: Russian Mil, RUS 0710 CIS-12, MPSK 12-tones 2-PSK 120Bd/200 (20Mar15) (AAI)
10638.0 EK9: Greek Military, GRC 0617 MIL 188-141A clg-Tis GEF (22Mar15) (AAI)
11032.0 ---: Russian Mil, RUS 0633 CIS-45, OFDM 45-tone modem 2PSK 40Bd/65.5Sh (22Mar15) (AAI)
11111.0 STAT154: Tunisian MOI Net, TUN 1227 MIL 188-141A clg-Tis STAT22 (20Mar15) (AAI)
11111.0 TUD: Tunisian MOI Net, TUN  1228 MIL 188-141A clg-Tis STAT22 (20Mar15) (AAI)
11408.0 ---: Russian Air Force (possibly REA4), RUS 0655 ARQ-FSK 100Bd/1000 reversals (22Mar15) (AAI)
13911.0 870: Enigma M03 1420 CW " 12293 27554 96868 T4962 = = 870/37" (20Mar15) (AAI)
14411.0 RDL: Russian Navy Smolensk,RUS 0655 F1A, FSK-CW (21Mar15) (AAI)
16684.5 OSY: Sailmail node Brugge, BEL 1455 PACTOR-III wkg WDF9923 "WDF9923 de OSY QTC 2 msg 13737 char" (22Mar15) (AAI)

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.

19 March 2015

Logs: 15-18 March

05512.0 4XZ: Israeli Navy, ISR 2205 MIL 188-110 Hybrid Modem messages (17Mar15) (AAI)
08534.0 UM01: Algerian Air Force, ALG 0732 MIL 188-141A clg-Tis QT01 -> MIL 188-110B OFDM 39-tones (16Mar15) (AAI)
08534.0 ER01: Algerian Air Force, ALG 0732 MIL 188-141A clg-Tis KM01 (16Mar15) (AAI)
09050.0 ---: unid 0803 MIL-188-110A/2400bps (16Mar15) (AAI)
09069.0 SPI324: Polish Military, POL 0703 MIL 188-141A clg-Tws LCR154 (18Mar15) (AAI)
10160.0 ---: Turkish Net, TUR 0738 MIL 188-141A AMD "<<[2015]/>A2005 0 6000 -1 1 ESN20359B0B0000 2015" (17Mar15) (AAI)
10370.0 SNB813: Polish Military, POL 0707 MIL 188-141A clg-Tis SPT24 (18Mar15) (AAI)
10658.0 3014 Turkish Civil defence, TUR 0743 clg-Tis 1020 + voice chat (17Mar15) (AAI)
11025.0 ---: Russian Mil, RUS 0745 USB RUS-ARQ/100/500 (16Mar15) (AAI) 
13841.0 ---: Russian Mil, RUS 1420 CIS-45, OFDM 45-tones 40Bd/62.5 HDR modem (18Mar15) (AAI)
19523.7 ---: Egyptian MFA, EGY 0700 USB ARQ/SITOR-A 100Bd/170 clg OOVQ (18Mar15) (AAI) 

17 March 2015

MIL STD-188-110 Appendix B, 39-Tones

"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. 


I messaggi in JT65 sono trasmessi in modalita' MFSK, piu' precisamente 65-FSK, ovvero usa 65 toni (da qui il suffisso "65") dove il tono piu' basso (a frequenza fissa) serve per la “sincronizzazione” fra Rx e Tx  mentre gli altri 64 toni servono per veicolare il messaggio. Dopo la codifica sorgente in 65-MFSK, e la relativa compressione, viene aggiunta la codifica di canale FEC, in maniera tale che un messaggio può essere recuperato con successo anche se alcuni "pezzi" di questo non vengono ricevuti. Con questo principio, i messaggi o vengono decodificati correttamente (con probabilità molto elevata) o non vengono decodificati.
JT65 si presenta in tre varianti: JT65-A, JT65-B e JT65-C che differiscono solo per lo shift fra i 65 toni e di conseguenza per l'ampiezza della banda occupata: e' facile vedere come questi valori quasi "raddoppino" al passare dalla modalita' A a quella C. Le tre varianti hanno comunque in comune la frequenza del tono di riferimento e mantengono costante la velocita' di manipolazione (baudrate) pari a circa 2.69 Hz.

Andiamo a vedere l'analisi dei tre segnali e la tabella riepilogativa dei risultati ottenuti.

misure di frequenza e velocita' di manipolazione del segnale in JT65-A

griglia MFSK, notare il variare dello shift (Delta) fra i 65 toni

misure di frequenza e velocita' di manipolazione del segnale in JT65-B 
griglia MFSK, notare il variare dello shift (Delta) fra i 65 toni

misure di frequenza e velocita' di manipolazione del segnale in JT65-C
griglia MFSK, notare il variare dello shift (Delta) fra i 65 toni

 tabella riepilogativa

Con le modalita' sopra viste, JT65 è stato progettato per consentire la trasmissione di un sufficiente numero di informazioni e il sub-moo JT65-A e' quello usato nelle bande radioamatoriali per scambiarsi brevissimi ma al contempo efficaci QSO con un minimo impiego di banda (~200 Hz): 


Punto di forza, non indifferente, è la possibilità di poter operare con potenze irrisorie, soprattutto sulle HF, dove il normale utilizzo avviene quasi esclusivamente in modalità QRP (2w-5w-10w).
Principio base della trasmissione e della conseguente ricezione in JT65 è che queste sono cadenzate ogni singolo minuto nel quale, però, i primi 46,7 secondi servono ad una stazione per trasmettere un messaggio con una lunghezza massima di 13 caratteri, mentre i restanti servono per completare il periodo con la relativa decodifica. E’ facile comprendere che le modalità di svolgimento di un QSO completo necessitano di alcuni minuti, parte dei quali verranno utilizzati dalla stazione 1 per le proprie trasmissioni (es. minuti dispari) ed i restanti dalla stazione 2 (es. minuti pari).
Per consentire il rispetto degli intervalli di trasmissione e ricezione occorre che i pc dei due corrispondenti (stazione 1 e 2) siano perfettamente sincronizzati con lo stesso orario, a tal riguardo occorrerà aver installato sul proprio PC un software gratuito di regolazione dell’orologio, molti utilizzano DIMENSION 4, reperibile gratuitamente su questo link:

JT65 puo' essere facilmente impiegato (per noi solo in ricezione) grazie all'utilizzo di alcuni software ovviamente specifici per JT65 quali JT65-HF HB9HQX-Edition, versione migliorata di JT65-HF.

screen di ricezione di JH65-HF

JT65 (submodi A,B,C) insieme a JT9, FSK441 e altri, fa' parte della famiglia del protocollo WJST orinariamente sviluppato da Joe Taylor K1JT per lo studio delle comunicazioni via tropo-scatter e EME (Earth-Moon-Earth). JT65 in particolare sfrutta le migliorie apportate a WJST per le comunicazioni in HF, da qui anche il nome JT65-HF solitamente usato per indicare il sub-modo JT65-A.

I due software usati in ambito JT65-HF sono questi qui sotto, a detta di tanti il secondo e' migliore:

sinosoidal OTH-Radar and Sounder

observed during last days on HF:

15 March 2015

Logs: 12-15 March

09052.0 ---: unid 0755 USB (cf) MIL 188-110A single-tone messages (13Mar15) (AAI)
09234.0 ZB01: Algerian Mil, ALG 0735 USB MIL 188-141A clg-Twas PA01 (13Mar15) (AAI)
09234.0 XK01: Algerian Mil, ALG 0738 USB MIL 188-141A clg-Tis PA01 + handshake (13Mar15) (AAI)
09234.0 FUO2: Algerian Mil, ALG 0750 USB MIL 188-141A clg-Tis PA01 + handshake and voice chat (13Mar15) (AAI)
09234.0 JT01: Algerian Mil, ALG 0753 USB MIL 188-141A clg-Tis PA01 (13Mar15) (AAI)
09289.0 X06: Russian Diplo, RUS 0725 MFSK 6-tones selcall aka 'Mazielka', sequence "214653" (13Mar15) (AAI)
09330.0 HM01: Cuban Number Station, CUB 0703 RDFT/AM spanish female + data bursts (13Mar15) (AAI)
09380.0 MV45: Algerian Mil, ALG 0819 USB MIL 188-141A clg-Tis PA50 + handshake and voice chat (13Mar15) (AAI)
10556.2 ---: Russian Mil, RUS 0740 USB CIS-12 link setup (14Mar15) (AAI)
10943.8 ---: unid NATO stn 1540 OFDM 16-tones modem, no Pilot-Tone (ANDVT variant ?) (12Mar15) (AAI)
12736.0 ---: Russian Mil, RUS 1505 USB FSK 100Bd/1000 reversals (14Mar15) (AAI)
20964.0 ---: Russian Mil, 0815 USB CIS-112, OFDM 112-tones modem DQPSK 22.22Bd/25.6 (15Mar15) (AAI) 

20981.0 ---: unid 0840 USB STANAG-4285/1200L crypto (15Mar15) (AAI)

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.

LINK-11 CLEW, conventional waveform

LINK-11 is identical with the US armed forces’ Tactical  Digital  Information Link A, TADIL and is defined by the United States Department of Defense as MIL-STD-6011.
LINK-11 comes in two waveroms: the original Conventional  Link  Eleven  Waveform (CLEW) and Single (serial) tone Link Eleven Waveform (SLEW).

The LINK-11 Conventional Waveform (CLEW) uses 16 tones with a tone spacing of 110 Hz and a doppler tone (on the left), the 14 data tones and then the synchronisation tone.

Number of channels: 14 +1 doppler-tone + 1 syncronization tone
Manipulation in the channels: DQPSK
Step between channels (frequency net/grid): 110 Hz
Manipulation speed: 75
Sampling rate of signals formation: 11025 Hz
Symbols length (LS) with CP, in samplings: 147
Length of defensive interval (LG), in samplings: 47
Symbols length (LU), block size IFFT/FFT, in samplings: 100 

12 March 2015

Logs: 05-11 March

05415.5 ---: Unid NATO stn 2050 NATO-75, FEC 2-FSK 75bd/850 crypto (05Mar15) (AAI)
08588.0 XSL: Japanese Navy  2025 modem 4-PSK 1500Bd aka 'Japanese Slot Machine' (09Mar15) (AAI)
09140.0 ---: unid Russian Mil, RUS 0850 2-FSK 100Bd/500 crypto (10Mar15) (AAI)
10074.0 5CIN2D: unid asset/network 1245 USB MIL-188-141A clg 5CIN1D + handshake
10370.0 SPT24: Polish Mil, POL 1231 USB MIL-188-141A clg-Twas SNB813 (11Mar15) (AAI)
10568.2 IDN: NCSA Naples, I 1430 USB/STANAG 4285/600L/3300 crypto (06Mar15) (AAI)
11000.0 RIW: Russian Navy HQ Moscow, RUS 2205 Cw "QYT 9 QS X 7640 K" (09Mar15) (AAI)
11226.0 233127: C-17 #03-3127, 305AMW McGuire AFB NJ 2054 USB MIL-188-141A clg-Twas CRO (10Mar15) (AAI)
11226.0 170039: C-5 # 87-0039 9th AS/436th AMW Dover AFB DE 2055 USB MIL-188-141A sndg (10Mar15) (AAI)
11226.0 ADW: USAF Andrews MD, USA 2058 USB MIL-188-141A sndg (10Mar15) (AAI)
12165.0 ---: unid Russian Mil, RUS 0805 ARQ 2-FSK 100Bd/500 crypto (10Mar15) (AAI)
12165.0 ---: NATO datalink 1420 USB OFDM 14-tones modem DQPSK aka 'LINK-11/TADIL-A' (11Mar15) (AAI)
18248.7 KWX57: US DoS Emergency & Evacuation network, USA 0847 USB MIL-188-141A sndg + voice check (11Mar15) (AAI)
18248.7 KWX57: US DoS Emergency & Evacuation network, USA 0848 USB MIL-188-141A clg-Twas KWS95 (11Mar15) (AAI)
12580.5 OSY: SailMail Node Brugge, BEL 1802 PacTOR-III DBPSK 2-tones clg Dutch Pleasure Ship REBEL "PF6269 de OSY"
13128.0 TAH: Istanbul Radio, TUR 1005 USB J3E male english "marmara" bulletin (07Mar15) (AAI)

10 March 2015

"The Cuban Lady" (HM01), 8 RDFT tones

HM01 is the Enigma designatore for number station "The Cuban Lady" and it's operated by Cuban Intelligence Directorate (DGI). As its name suggestsd Mixed Mode V02a (voice) + SK01 (RDFT) boadcsated in AM, they use an hybrid mode composed of voice (V02a) in AM modulation and data-transfer in RDTF mode (SK01), where RDTF stands for Redundant Digital File Transfer, a differential phase shift keying mode  that has never become a standard in comunications.

The RDTF portions of the signal are created using the free program DIGTRX, which can be used by anyone to retrieve the contents, which are .TXT files with binary, encrypted data.  Cuban intelligence is currently its only user (as far as we know).


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.