Digital modes are the topic of this week’s Amateur Extra exam question…. [E8C13]
What is one advantage of using JT-65 coding?
A. Uses only a 65 Hz bandwidth
B. The ability to decode signals which have a very low signal to noise ratio
C. Easily copied by ear if necessary
D. Permits fast-scan TV transmissions over narrow bandwidth
Well, what the heck is JT-65 coding? JT-65 is a digital mode of ham radio. Initially developed for use in EME (Earth-Moon-Earth) VHF contacts, it was discovered that it could be used with great success on HF at low power.
I’ve personally used JT-65 at relatively low power to make QSO’s all over the world.
The great thing about JT-65, is the ability to pull a readable signal from a lot of noise. You may not even be able to hear it with your ears, but the software is able to “see” the signal in the waterfall (the display of the audio frequencies at the top of the image.) This is because of the relatively low amount of information (only 13 characters!) transmitted over a long amount of time (47 seconds!) with plenty of error correction and redundancy built in.
The answer, is, therefore, B. The ability to decode signals which have a very low signal to noise ratio
You should head on over to JT-65.com to get your JT-65 reference card, and stick around, eventually I’ll be releasing a JT-65 mini-course!