Digital Communications - JT-65

Digital communications can go farther than phone (voice) communications with less power and with some digital protocols you can make more contacts.  Digital communications, in its simplest form is CW - continuous wave radio transmissions using Morse code.

For more complex digital communications you need some gear.   Computers can be interfaced to Ham Radio equipment where the serial or USB port can control the transmitter and the audio sound card sends and receives encrypted signals.   Systems currently supported are Windows PC and Linux.   Mac users may have to figure it out and wing it with the help emulation software.

The easiest interface that I have experience with is the Rigblaster by West Mountain Radio.    It is simply a box where you connect the audio out  and the USB or Serial Port of your computer to the microphone input of your radio.   The Rigblaster may be ordered in different configurations depending on your radio.

Information for the Rigblaster Plus 2 can be seen at:
http://www.westmountainradio.com/product_info.php?products_id=rigblaster_plus2


Most HF radios have a VOX switch and if you do not want to use the USB or Serial Port to trigger the transmitter just set the VOX but disconnect the microphone.

That is pretty much the hardware needed the only other thing you need is a tool for the decryption of the signals, which are performed by computer software.

How it works:

JT-65 is one digital protocol where an average conversation over Ham Radio (QSO) can take about 6 to 7 minutes, signals travel a long distance with low power and a Ham can easily contact other Hams in all 50 states as well all over the world.   I learned about JT-65 last January and in a few months logged in over 200 contacts.  Once you get the hang of JT-65 it can be a lot of fun.

The JT-65 signal begins at 2 seconds past the minute and sends a 13 character message for 45 seconds.   The software on the receiving end decodes the message and gives the receiver the option of answering the sender.   The frequency set aside for most operations is at the top of the band and near .076 past the top.
Two bands frequently used in the U.S. are 40 meter  @ 7.076Mhz and 20 meter @ 14.076Mhz.

Where to get it:

A guide to the bands and frequencies for JT-65 can be found at:
 http://hflink.com/jt65/

 JT-65 is time sensitive and you must coordinate the minutest and seconds of your computer clock to ZULU or Greenwich Mean Time.    A great resource for setting your clocks to Zulu is at:
http://zulutime.net/

The software for JT-65 is available free on the Internet at various sites.
I personally use the software found on the Sourceforge site:
http://sourceforge.net/projects/jt65-hf/

Another software package can be found on the Princeton University site:  http://physics.princeton.edu/pulsar/K1JT/index.html


I found some great videos on YouTube demonstrating JT-65:

There is a website where you can check your propagation called PSK REPORTER.   You can enter your call letters, protocol and send a low powered CQ.  In about 20 seconds you will be able to determine if you are using enough power to get to where you want to contact.    The site is at:
http://pskreporter.info/pskmap.html 

This is where my 30wt signal went on a morning with poor propagation:

On better days:

The photo above shows the signal report for my Icom IC-740 with a simple dipole antenna.  This was a 30 wt  JT-65 transmission that reached all over the US as well as a station in New Zealand.