Topband: Testing FST4 on 160m

[Jim Brown]

On 2/8/2021 9:43 PM, James Wolf wrote:
> I'm not understanding the time setting on FST4.
> Does the station calling CQ set the time duration of FST4 and the receiving
> station automatically detect that time setting and mimic it, or do both
> stations need to start with the correct setting?
> I'm not seeing this information in the documentation.

Hi Jim,

The guys writing both the code and doc are super smart and excellent 
writers, but they fail to realize how little the rest of us know. :)

I know the answer because I asked on their email reflector -- each time 
duration is structurally different, so if I'm set for 60 sec (which I 
am), I'll see 15 and 30 sec signals on the spectrum display, but I won't 
decode them, and those stations won't decode me. The reason that's true 
is that each time duration also uses different tone spacing. And signal 
to noise ratio improves by 3 dB per doubling of time.

I've chosen 60 sec because I'm trying to work either 1) SC and VT to 
finish QRP WAS or 2) at full power, new EU countries. At this point, 
very few have adopted the mode. Most of the time I call CQ at 5W, but as 
the evening wears on I turn on the amp and crank it up to 1 kW. Even 
running power, I've been decoded by fewer than ten stations in an evening.

It's a great mode though, almost 20 dB advantage over CW with great ops 
on both ends.

73, Jim K9YC