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Author Topic: FT8 digital comms mode  (Read 2512 times)

NCGunDude

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FT8 digital comms mode
« on: October 31, 2017, 12:55:16 PM »
I've been using PSK-31 for a couple of years, and tried JT-9 and JT-65. Last weekend updated WSJT-X on my linux box and started making contacts.

FT8 supports up to 28 characters in 15 second send/receive intervals. It's necessary to keep your clock synced within 1 second of UTC. According to the documentation, FT8 is not as sensitive as the JT protocols, but is much faster.

While it's a fun, fast paced protocol, I can see it's usefulness in a grid down situation for sending abbreviated messages.

The time syncing issue has me thinking how would one accomplish syncing their computer without an internet connection?

Anyone else trying FT8 and what do you think?

gil

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Re: FT8 digital comms mode
« Reply #1 on: October 31, 2017, 01:04:19 PM »
There are much better modes for chat than FT8.
Those "chatless," time-dependent modes are useless for prepping.
FSQ or Olivia come to mind, much better. I should be testing them soon.

Gil.

RadioRay

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Re: FT8 digital comms mode
« Reply #2 on: November 01, 2017, 10:37:36 PM »
For communication, I've found that CONTESTIA 4/250 has a very good resilience -vs- speed and bandwidth. For communication, you rarely if even need the full ASCII set.  Using only uppercase, nimbers and most punctuation, CONTESTIA has a shorter data set (bits per letter) and so sends fewer bits for the same letters. It uses a STRONG FEC like OLIVIA and works well into the noise.  Unlike the 2-way beacon modes, which at first seem great for prepping, there is no timebase needed.  Most of the 'low power' beacon modes use internet clocks or GPS slaving - both of which are questionable in a SHTF situation. I did a full evaluation and the time synch is a major problem - after all, if we HAVE the internet, we'd use the internet.

My 0.02 Euros worth - please adjust for currency devaluation, Brexit & etc.

 de RadioRay ..._  ._

Ps. Remember, for digital QRP,  include the COMPUTER power drain in the power budget calculations. Morse uses no computer, other than the brain.
« Last Edit: November 01, 2017, 10:40:07 PM by RadioRay »
"When we cannot do the good we would, we must be ready to do the good we can."  ~ Matthew Henry

gil

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Re: FT8 digital comms mode
« Reply #3 on: November 02, 2017, 04:16:36 AM »
Quote
I've found that CONTESTIA 4/250 has a very good resilience -vs- speed and bandwidth.

Thanks Ray, I remember you mentioned it before. I'll test it as well. What an awful name though :o

Gil.

RadioRay

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Re: FT8 digital comms mode
« Reply #4 on: November 03, 2017, 10:00:12 PM »
"What an awful name though" :o

Mooooo- ha ha ha ha!  True

of course, a REAL CONTESTERS mode would just be hardwired to send "5NN" and maybe their call - 20 KHz high - of course.

"When we cannot do the good we would, we must be ready to do the good we can."  ~ Matthew Henry

gil

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Re: FT8 digital comms mode
« Reply #5 on: November 04, 2017, 04:01:43 AM »
Quote
of course, a REAL CONTESTERS mode would just be hardwired to send "5NN" and maybe their call - 20 KHz high - of course.

I think the software would be locked on QRP calling frequencies and 14300. Time between calls would also be hardcoded to 0.1 second. Minimum power 500 Watts.

Gil.

Mr. White

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Re: FT8 digital comms mode
« Reply #6 on: February 28, 2018, 09:43:30 PM »
I have been operating Olivia for years and it is robust and easy. I have seen it copy when I cant see it in the water fall. It can be pretty slow, but it passes clear correct traffic. A mode that can be used in a round table.

But really CW is still King. I can carry the radio in my shirt pocket, run it from my small solar panel. Without the need of a computer. 

gil

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Re: FT8 digital comms mode
« Reply #7 on: March 01, 2018, 05:06:58 AM »
What's needed in a prepping digital mode is something that can be left unattended and save messages... Winlink does that, but unfortunately only exists on Window$. It is also not that simple to use. I don't know of any other mode that could do the same.

Gil.

Andywragg

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Re: FT8 digital comms mode
« Reply #8 on: April 10, 2018, 05:41:37 AM »
Now I've proven my QTH installation after several days of successful FT-8 operation I'm going to have a go at one of the live chat modes.  I found FT-8 very useful in being able to spot the landfall of my signals (using PSFKReporter), using a couple of bands at different times of day. And in establishing contact with other stations but as you say we need to be able to pass more information than location and signal reports.

Rather than ruling out any 1 mode I think using a combination of (for instance) FT-8 to establish a net  (probably to a prearranged sched) followed by a period of time passing live traffic using a live chat mode, would work to some degree.
Once a 'STAB in the Dark'
M6UAW

gil

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Re: FT8 digital comms mode
« Reply #9 on: April 10, 2018, 05:48:18 AM »
APRS Messenger might be worth a try for unattended messaging. Julian has a video on it. I no longer have Window$ so not sure if it will run in Linux/Wine.

Gil.

Andywragg

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Re: FT8 digital comms mode
« Reply #10 on: April 10, 2018, 06:06:38 AM »
Hi Gil,

It's installed I have yet to try it out though (APRS Messenger). BTW, all of my observed landfall so far has been well past your QTH, I only just got France in the log last night but that was JN23WD. I'm not finished testing the shorter bands (17m and up) so hopefully that might yield some shorter contacts. 

Finland on the other hand is well within my sights and I've already worked an OH station, just not the RIGHT OH station.....
Once a 'STAB in the Dark'
M6UAW

gil

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Re: FT8 digital comms mode
« Reply #11 on: April 10, 2018, 06:22:01 AM »
Yep, when I lived in Florida I rarely got Western Europe... Often Russia and Eastern-block countries... It probably has to do with the length of the skips, refraction angle.

Gil.

vwflyer

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Re: FT8 digital comms mode
« Reply #12 on: April 15, 2018, 11:35:54 AM »
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What's needed in a prepping digital mode is something that can be left unattended and save messages...
Here's my limited understanding of store and forward systems. If somebody wants to correct me or expound, I'm anxious to learn.
Every store and forward needs a running radio connected to a server. Most of them these days use servers on the internet so when the internet goes down so does the server. Some have local servers, like many Packet radio repeaters designed to work without the grid or internet. Winlink and APRS can use local servers as well but to my knowledge, most use internet servers. In any case a grid down situation is going to require a powered radio with a local server that can run without grid power. Having someone else do that for you can be convenient in that you don't have to leave your computer and radio running all the time. But then the success of you getting the message depends on someone else's setup working.
For keeping messages locally at my own QTH, using my own radio and computer, I would currently go with FSQ. It's designed for this. Messages can be sent directly to you and give you an alert when someone tries to contact you. The messages are stored so long as the software is running.