[Elecraft] 6m Meteor Scatter

[Jim Brown]

On 12/6/2018 12:59 AM, eric norris via Elecraft wrote:
> MSK144 encodes and decodes very differently than FT8.

Lots of great info in this post. I'll expand on this comment. FT8, JT65, 
and JT9 are noise reduction modes -- the transmit the same message 
several times in the message cycle, and they use the entire message 
cycle to do that. They are designed to work on a path that is weak, but 
exists for most of the message cycle.

MSK144, and it's predecessor FSK441, transmit the same message over and 
over again in segments of a few hundred msec. All it takes is for ONE of 
those few-hundred msec transmissions to get through. They are designed 
for a path that may be there for only a few hundred msec or, if we're 
lucky several chunks of a few hundred msec -- that is, when a meteor has 
ionized a region of the atmosphere that reflects our signal to the other 
guy, and, at some later time, the other guys's signal to us. As I 
understand it, MSK144 does SOME noise reduction, but not much.

Another great thing about the implementation of MSK144 is that we can 
choose TX cycles of 5-30 msec. Last I looked, most stations were using 
15 sec.

The most surprising MSK144 QSO I've made was with a guy doing a 6M grid 
expedition through nowhere NV, a path of roughly 400-500 miles, 
mid-afternoon this past summer. The first stages (three, I think) were 
done with him driving down the road transmitting 100W into a vertical. 
He eventually parked and set up a small Yagi for the last two sequences 
to finish the QSO. I worked him to fill in a total of four or five 
nowhere grids, and failed on five others.

Last I looked, K1JT was suggesting that MSK144 be used where we had 
previously used ISCAT, another mode designed for tropo scatter.

To understand these propagation modes, study the ARRL Handbook and  
Antenna Book. It makes very interesting reading, and using those modes 
can be a lot of fun.

Anyone who says that these digital modes and propagation modes are easy 
has never done it. I've been doing it for about five years, and there IS 
a learning curve, and the more you know about the digital modes and the 
propagation modes, the successful you are, and the more fun you have.

I've never tried 2M MS -- I'm in a very dense redwood forest (the trees 
top out around 250 ft and my Yagi is at 125 ft) and those trees are 
increasingly strong absorbers of RF with increasing frequency.

73, Jim K9YC