Hello. Today I will tell how to make a digital communication session with low power.
There is such a digital connection type JT65.
JT65 is an amateur radio QSO communication protocol developed by Joe Taylor, K1JT. JT65 has 3 submodes: JT65A, JT65B, and JT65C. The most popular submode of JT65 is JT65A. JT65 gets ’65’ from the 65 tones it uses.
Each transmission begins at t = 1s after the start of a UTC minute and finishes at t = 47.8 s. Each transmission must begin within the first 4 seconds of the minute to be decoded. Multiple stations transmit on the same carrier using both FDM and TDM methods. Initiating stations choose either the Even or Odd minute to transmit and responding stations transmit on the opposite minute.
A sync (low) tone is to mark the lower boundary of each station’s signal. The synchronizing tone is at 1270.5 Hz. The initiating station is responsible for choosing an offset that does not conflict with another station’s signal. JT65 uses 126 contiguous time intervals, each of length 0.372 s (4096 samples at 11025 samples per second). Within each interval, the waveform is a constant-amplitude sinusoid at one of 65 pre-defined frequencies, and frequency changes between intervals are accomplished in a phase-continuous manner.
In simple words, the transceiver joins a computer or phone with a program that transmits and receives data in an audio format by the protocol JT65. The transceiver is tuned to one of the dedicated frequencies for the JT65.
- 160m: 1838.0 kHz USB
- 80m: 3576.0 kHz USB
- 40m International: 7039.0 kHz USB
- 40m USA: 7076.0 kHz USB
- 30m: 10139.0 kHz USB.
- 20m: 14076.0 kHz USB
- 17m: 18102.0 kHz USB.
- 17m Alternate: 18098.0 kHz USB
- 12m: 24917.0 kHz USB
- 6m EME: 50276 kHz USB
In my case, 14.076 MHz. The transfer starts from the first second and continues until the 47th. After a minute of transfer, the program will listen to the broadcast for the next minute and then transmit for the next minute again. You can choose when to start transferring data during a paired or not even minute. The station, which wants to connect with you, also chooses a minute to get your transmission in the moment when you listening. You can recognize the JT65 by the characteristic sound.
It is possible to transfer 13 characters in one minute. This seems to be not a lot, but this is way the greater sensitivity of this protocol is achieved due to the use of a special protocol for encoding and error correction.
Let’s return to our communication session as called QSO. I’m UR5TLZ I’m having it with the Spanish EA1BUP station
The order of the receipt of messages from the bottom to up. The distance between the correspondents is 2566.42 km. I have a transmission power of 15W and Spaniard ap to 30W. After the communication, radio amateurs exchange postcards as called QSL card
I got this.
And i sent such to Spaniard.
In this case, the service of electronic QSL postcards was used www.eqsl.cc
The another convenient moment of digital communications is that you are able to view propagation of your signal with the help of the service. https://pskreporter.info/
He displays on the map with the clouds who, where and how long ago stations heard your signal.
That’s all good luck 73!