Gravacions de modes digitals utilitzats pels radioaficionats

Gravacions mp3 d’alguns modes digitals (1) (2) més utilitzats pels radioaficionats.


Recepció de BPSK a 14.070 kHz. amb el programa MixW 3.1.1


PSK31 or “Phase Shift Keying, 31 Baud” is a popular computer soundcard generated radioteletype mode, used primarily by amateur radio operators to conduct real time keyboard-to-keyboard chat, most often using frequencies in the high frequency amateur radio bands (shortwave). PSK31 is distinguished from other digital modes in that it is specifically tuned to have a data rate close to typing speed, and has an extremely narrow bandwidth, allowing many conversations in the same bandwidth as a single voice channel. This narrow bandwidth also concentrates the RF energy in a very narrow bandwidth, allowing relatively low-power equipment (25 watts) to communicate globally using the same skywave propagation used by shortwave radio stations.PSK31 was developed and named by English amateur radio operator Peter Martinez (call sign G3PLX) and introduced to the wider amateur radio community in December 1998.
The 31 baud BPSK modulation system used in PSK31 was introduced by Pawel Jalocha (SP9VRC) in his SLOWBPSK program written for Motorola’s EVM radio. Instead of the traditional frequency-shift keying, the information is transmitted by patterns of polarity-reversals (sometimes called 180-degree phase shifts). PSK31 was enthusiastically received, and its usage grew like wildfire worldwide, lending a new popularity and tone to the on-air conduct of digital communications. Due to the efficiency of the mode, it became, and still remains, especially popular with operators whose circumstances do not permit the erection of large antenna systems, the use of high power, or both.

Radioteletype (RTTY) is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations connected by radio rather than a wired link. These machines were later superseded by personal computers (PC) running software to emulate teleprinters. Radioteletype evolved from earlier landline teleprinter operations that began in the middle1800. The US Navy Department successfully tested printing telegraphy between an airplane and ground radio station in 1922. Later that year, the Radio Corporation of America successfully tested printing telegraphy via their Chatham, Massachusetts, radio station to the R.M.S. Majestic. Commercial RTTY systems were in active service between San Francisco and Honolulu as early as April 1932 and between San Francisco and New York City by 1934. The US military used radioteletype in the 1930 and expanded this usage during World War II. From the 1980s, teleprinters were replaced by computers running teleprinter emulation software.

The term radioteletype is used to describe both the original radioteletype system, sometimes described as “Baudot”, as well as the entire family of systems connecting two or more teleprinters or PC using software to emulate teleprinters, over radio, regardless of alphabet, link system or modulation. In some applications, notably military and government, radioteletype is known by the acronym RATT (Radio Automatic Teletype).

JT65, developed and released in late 2003, is intended for extremely weak but slowly varying signals, such as those found on troposcatter or Earth-Moon-Earth (EME, or “moonbounce”) paths. It can decode signals many decibels below the noise floor in a 2500 Hz band (note that SNR in a 2500 Hz. band is approximately 28 dB lower than SNR in a 4 Hz band, which is closer to the channel bandwidth of an individual JT65 tone), and can often allow amateurs to successfully exchange contact information without signals being audible to the human ear. Like the other modes, multiple-frequency shift keying is employed; unlike the other modes, messages are transmitted as atomic units after being compressed and then encoded with a process known as forward error correction (or “FEC”). The FEC adds redundancy to the data, such that all of a message may be successfully recovered even if some bits are not received by the receiver. (The particular code used for JT65 is Reed-Solomon.) Because of this FEC process, messages are either decoded correctly or not decoded at all, with very high probability. After messages are encoded, they are transmitted using MFSK with 65 tones.
Operators have also begun using the JT65 mode for contacts on the HF bands, often using QRP (very low transmit power); while the mode was not originally intended for such use, its popularity has resulted in several new features being added to JT65-HF-HB9HQX in order to facilitate HF operation.

Hellschreiber (HELL) or Feldhellschreiber (also Hell-Schreiber named after its inventor Rudolf Hell) is a facsimile-based teleprinter invented by Rudolf Hell. Compared to contemporary teleprinters that were based on typewriter systems and were mechanically complex and expensive, the Hellschreiber was much simpler and more robust, with only two moving parts. It has the added advantage of being capable of providing intelligible communication even over very poor quality radio or cable links, where voice or other teledata would be unintelligible.
The device was first developed in the late 1920, and saw use starting in the 1930, chiefly being used for land-line press services. During WW2 it was sometimes used by the German military in conjunction with the Enigma encryption system. In the post-war era, it became increasingly common among newswire services, and was used in this role well into the 1980. In modern times Hellschreiber is used as a communication mode by amateur radio operators using computers and sound cards; the resulting mode is referred to as Hellschreiber, Feld-Hell, or simply Hell.

FT8 (Franke-Taylor design, FSK8 modulation) was created by Joe Taylor, K1JT and Steve Franke, K9AN. It is described as being designed for “multi-hop ES where signals may be weak and fading, openings may be short, and you want fast completion of reliable confirmable QSO’s”. Compared to the so called “slow modes” (JT9, JT65, QRA64), FT8 is a few decibels less sensitive, but allows completion of QSOs four times faster. Bandwidth is greater than JT9, but about one-quarter of JT65A and less than one-half of QRA64. Compared with the “fast modes” (JT9E-H), FT8 is significantly more sensitive, has much narrower bandwidth, uses the vertical waterfall, and offers multi-decoding over the full displayed passband. Features not yet implemented include signal subtraction, two-pass decoding, and use of a priori (already known) information as it accumulates during a QSO.

Demostració del mode digital FT8 a càrrec d’EB3DKE

La Federació Catalana de Radioaficionats farà una demostració de la modalitat digital FT8 dins del congrés anual de les associacions que en formen part. La demostració es farà el dissabte 24 de novembre de 2018 a 2/4 de 10 del matí a la seu del Ràdio Club del Vallès, EA3RCH, a càrrec d’en Joan Ramon, EB3DKE.

El mode FT8 és un sistema digital desenvolupat pel radioaficionat Joe Taylor, K1JT i incorporat al programa WSJT-X tot i que la majoria de radioaficionats utilitzen el programa JTDX del radioaficionat rus UA3DJY, Igor Chernikov. El JTDX que és un derivat de l’original WSJT-X i funciona més bé, ja que ofereix una sensibilitat de recepció molt més alta. En Joe és també l’inventor d’altres modes digitals, el JT9, QRA64, JT65 i altres, pensats per a senyals molt febles, amb rebot múltiple, obertures curtes i amb molt esvaïment del senyal on els comunicats s’han de completar amb molta rapidesa.

Nou reemissor DMR+ connectat al reflector català 4714

Des d’avui ja està disponible el nou reemissor en la modalitat DMR+ connectat al reflector català 4714. Aquestes són les dades:

  • Indicatiu: ED3YAB
  • Freqüència: 439.412,5 MHz. (-7,6 MHz.)
  • Modalitat: DMR+ | Slot 2 | Color 1 | TG9
  • Cobertura: Anoia, Bages, Berguedà, Baix Llobregat i Vallès Occidental.

El reflector català DMR+ 4714 forma part de la Xarxa Digital Catalana DMR+ gestionada des del servidor IPSC2 Catalunya. Per tant, deixem d’utilitzar totalment els servidors espanyols DMR+_EA-MASTER-CAT i DMR+_IPSC2-SPAIN

Configuració bàsica del programa JTDX per al mode digital FT8

Des de fa un temps han adquirit molta popularitat l’ús dels modes digitals a les bandes d’HF especialment el JT65, JT9 i recentment l’FT8 i el T10. Aquests modes es caracteritzen per permetre fer comunicats mundials a llarga distància amb potències molt baixes i antenes modestes.

Per a emetre en aquests modes digitals hem d’utilitzar una interfície com el Sound Card adapter 3002 (molt econòmic) o bé el RigExpert TI-5000. La configuració és extremadament fàcil. La primera vegada que es connecta a l’ordinador (Windows 7, 8 o 10) el sistema operatiu instal·la automàticament els “drivers” i crea un port sèrie (COM) que s’utilitzarà per al control del PTT de l’emissora, és a dir, per commutar l’emissió i la recepció (TX/RX).

RigExpert TI-5000

Per als modes digitals JT65, JT9, T10 i FT8 hem d’instal·lar el programa JTDX desenvolupat per UA3DJY (Igor Chernikov) i el seu equip de col·laboradors. Descarreguem el programa JTDX i procedim a la seva instal·lació.

Iniciem el programa i prement la tecla F2 (o també el menú “File” i després “Settings”) i entrem a la configuració “General”. Introduïm el nostre indicatiu i el QTH locator i repassem les configuracions marcades en color vermell.

Menú “General”


Anem al menú “Ràdio” i configurem el control del PTT marcant l’opció RTS i el número de port COM corresponent de la nostra interfície. (El número del port COM el podem veure a l’administrador de dispositius del tauler de control del Windows).

Menú “Ràdio”


Anem al menú “Àudio” i configurarem l’entrada i la sortida d’àudio. En el menú desplegable veurem les targetes de so que tenim instal·lades, la pròpia de l’ordinador i la que tenim connectada a l’USB, sigui el Sound Card Adapter 3002 o el RigExpert TI-5000. Seleccionarem la corresponent, és a dir, la que està connectada a l’ordinador a través de l’USB que, generalment, porta per nom “USB Àudio Codec“.

Menú “Àudio”


A partir d’aquest moment si seleccionem el mode FT8 en el programa JTDX i tenim l’equip connectat i sintonitzat en una freqüència d’FT8, per exemple, 14.074 USB, (USB, Banda Lateral Superior) començarem a rebre els senyals. És imprescindible que tinguem el rellotge de l’ordinador a l’hora exacta, minuts i segons.

També és important habilitar el menú “Enable automatic logging of QSO”, ja que d’aquesta forma tots els comunicats es desaran de forma totalment automàtica.

Menú “Reporting”


És important repassar els menús indicats amb la fletxa. Aquests menús han d’estar habilitats, quedant de color verd. Amb les tecles AutoSeq i AutoTX habilitades, el programa realitzarà el comunicat de forma automàtica sense que l’operador hagi d’intervenir.

Ara ja podem gaudir de l’FT8, un revolucionari mode digital amb el qual es poden contactar tots els països del món amb poca potència i molta rapidesa i comoditat.

Trobada de radioaficionats, dinar i lliurament de premis del concurs Comarques Catalanes

El pròxim 17 de novembre de 2018 l’Associació de Radioaficionats de Catalunya (ARCAT) convoca la trobada de radioaficionats, dinar i lliurament de premis del concurs Comarques Catalanes dels anys 2017 i 2018 al restaurant Solers de Santpedor (Bages). | Menú: 26 €

Primer plat:

  • Torradetes de pa amb tomàquet i pernil de gla
  • Amanides amb formatge fresc i fruits secs
  • Broquetes de pollastre a la milanesa
  • Coques de pasta de full amb escalivada
  • Cuetes de llagostins arrebossades
  • Mini pizzes de tonyina

Segon plat a triar:

  • Opció 1: Bacallà amb samfaina
  • Opció 2: Fricandó de vedella amb xampinyons
  • Opció 3: Cuixes de pollastre desossades amb prunes i pinyons
  • Opció 4: Mero amb crema d’ametlles

Postres a triar.