Help Decoding Digital Modes (Using FLDigi)

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Murphy625

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I'm using an ICOM746 hooked to a laptop through a USB sound card.

For several nights now, I've been trying to decode various digital signals on the 40 meter band..

I'm using FLDigi and starting to get a handle on the controls.. My problem is that with the exception of a few successful CW attempts, I'm not having much luck.

Could I have a radio setting that is incorrect? A filter set incorrectly that would prevent the software from doing its thing? A tone setting or some other non-newbie-obvious setting that is a common mistake?

I'm finding that most of the CW signals I'm finding are on LSB.. and yet my radio has a button for CW/RTTY but it would seem that it degrades the signal, not help it.

A lot of the signals I'm hearing sound like CW but are way faster than a human could achieve.. These are CW done by software right?

Thanks
 

ka3jjz

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And a great many digital modes, too.

And since we're talking digital modes in the amateur radio service, that's where this will go. Onward...

Mike
 
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ka3jjz

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You should also know that while FLDigi covers a lot of modes, there are several that it doesn't - for example, ALE (MultiPSK does), FT8 ( a newer weak signal mode) and various forms of PACTOR (MultiPSK only handles PACTOR 1)

Our Digital Decoding FAQ has links for descriptions (and where known, sonograms and software) for almost all of these and a lot more.

I would suggest learning to copy 1 mode at a time - don't try to do everything at once. It will overwhelm you. Learn how to do CW first, since I think that was your mode of interest, then move over to something that's popular - say PSK31. Then move onto something else once you've learned that

Mike
 

ka3jjz

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We are restricted to certain segments of the bands for CW and data operations. This page gives you a good summation, so you have something of a guide for tuning...

Frequency Allocations

Mike
 

Murphy625

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And did you check this out - there's a beginners' guide, sonograms of the various modes, and more...

start [fldigi-wiki]
I don't think I went to that exact page, but yes, I downloaded the manual and even downloaded the entire directory with all the waterfall and sound examples so I can click on them without waiting for my internet to load a sound file. In other words, the website is loaded on my laptop but I don't have to connect to the internet to browse it.
I've spent several days now reading and learning.. I am not licensed to transmit.. I just want to learn to listen.
 

Murphy625

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We are restricted to certain segments of the bands for CW and data operations. This page gives you a good summation, so you have something of a guide for tuning...

Frequency Allocations

Mike

Yup, I have that information as well.. its my little "cheat sheet".. Mine looks different, but its the same information.
 

Murphy625

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Ok.. a bit of a breakthrough tonight.. just figured out there's an entire CW language that consists of a bunch of abbreviations that when strung together, looks like garbled code.

Seems as though FLDigi has been doing its job and that CW is closer to a secretary's shorthand or court reporter than it is the English language.

Wow.. the CW folks make the kids texting on their cell phones look like amateurs.. heck, they even put the military guys to shame.. and military folks love their abbreviations.
 

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K4EET

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Ok.. a bit of a breakthrough tonight.. just figured out there's an entire CW language that consists of a bunch of abbreviations that when strung together, looks like garbled code.

Seems as though FLDigi has been doing its job and that CW is closer to a secretary's shorthand or court reporter than it is the English language.

Wow.. the CW folks make the kids texting on their cell phones look like amateurs.. heck, they even put the military guys to shame.. and military folks love their abbreviations.

I got a chuckle out of your post and I'm still giggling. Yup, CW ops have their own shorthand to keep actual words per minute (WPM) higher. Keep at it and you'll be an expert in no time.

FLDigi is a good program. You might also be interested in WSJT-X (https://physics.princeton.edu/pulsar/k1jt/wsjtx.html) by Joe Taylor, K1JT, who developed FT-8 among other protocols like JT9 and JT65. While those modes are not really complete conversations like CW, RTTY and PSK31 would be, they are known for getting a minimal amount of information through quickly in a narrow bandwidth under less than optimal radio frequency (RF) conditions.

But like what was said before, focus on a single mode and perfect identifying and copying that mode before moving on to the next. Be sure to look up some of the history and technical aspects of the mode while you are at it to give you a well-rounded understanding of each mode (why it was first developed, what/when it is best used for, etc.).

Enjoy your travels and don't hesitate to ask questions if needed. There are no dumb questions when you are truly trying to learn something.

73 (best wishes in ham lingo), Dave K4EET
 

ka3jjz

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Hello Mike, in addition there is a frequency allocation sheet on the Icom America website that, to me, is a little more comprehensive. Take a look, its pdf, first download...

https://www.icomamerica.com/en/downloads/default.aspx?Category=352

Appreciate the link, Barry, but there have been some changes since this was published. It fails to mention that the FCC has opened up the 60m channels to data operations, not just CW. I also think the 2200 and 630 meter ops are now allowed, as long as you register with the Utility council first and there's a power limit if you are closer than 469 miles (???) to the Russian border

What I would really like to see - and it would be useful for the wiki's page on the subject - is a breakdown of which modes are used on which frequencies. .It's not a free for all - there is something of a 'gentleman's agreement' on where you should run PSK31, Olivia, etc.

Mike
 

Murphy625

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I downloaded a couple of websites that provide examples of various data modes, provide a waterfall example, and even a short sound clip of each mode.

Last night, somewhere on the lower side of the 40 meter band, I think I found an MFSK signal that sounded almost exactly like what is demonstrated on this website:
DigitalModes
It kind of sounded like one of the higher bandwidth modes like MFSK16 but the trace was only around 60hz wide like a BPSK31.
There seemed to be some kind of conversation going on as I sometimes had 3 or 4 traces on the waterfall at once and all at different frequencies. Some were higher pitched on the right side of the waterfall, some at a lower pitch on the left side.. and the one in the middle seemed to do most of the transmitting. Sometimes, there were three or four simultaneously.

I did everything I could do to decode these and never even came close.. Tried the MultiPSK and FLDigi, and every protocol I could find.. Obviously I knew some protocols wouldn't work as the signal wasn't even close.. But after reviewing all the samples, I think it was the MFSK.. I just can't figure out why I'm not able to decode them.

I must have some setting incorrect somewhere.. are there specific radio filtering settings that must be used?
 

Murphy625

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I got a chuckle out of your post and I'm still giggling. Yup, CW ops have their own shorthand to keep actual words per minute (WPM) higher. Keep at it and you'll be an expert in no time.

FLDigi is a good program. You might also be interested in WSJT-X (https://physics.princeton.edu/pulsar/k1jt/wsjtx.html) by Joe Taylor, K1JT, who developed FT-8 among other protocols like JT9 and JT65. While those modes are not really complete conversations like CW, RTTY and PSK31 would be, they are known for getting a minimal amount of information through quickly in a narrow bandwidth under less than optimal radio frequency (RF) conditions.

But like what was said before, focus on a single mode and perfect identifying and copying that mode before moving on to the next. Be sure to look up some of the history and technical aspects of the mode while you are at it to give you a well-rounded understanding of each mode (why it was first developed, what/when it is best used for, etc.).

Enjoy your travels and don't hesitate to ask questions if needed. There are no dumb questions when you are truly trying to learn something.

73 (best wishes in ham lingo), Dave K4EET

Oh well that's just dandy! So I have the CW Decoding software, (thanks to some seriously dedicated ham operator folks who make it free), and now what I need is decoding software to translate the decoded CW...

Does it end somewhere? LOL I'm going to have to print out a cheat sheet for all their abbreviations.. Still trying to figure out what 5NN is for.

Seriously though, when trying to lock onto a (non CW) data mode signal, in what order are things done? For instance, the first would be to tune the radio to get as strong a signal as I can get.. Then fire up the digital modes software and check out the waterfall.. How much bandwidth is the signal using? Is it taking up 50 or 60 hz? Or is it spread out over 200 or 300 hz? Is it a single trace, or is the signal composed of more than one trace?
Then, I reference the website page that has all the audio samples to find something that sounds similar and a waterfall that looks somewhat the same. From there, I try to match the protocol with the bandwidth..

What am I missing? It must be something but I'm not getting anywhere.
 

K4EET

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<snip> Seriously though, when trying to lock onto a (non CW) data mode signal, in what order are things done? For instance, the first would be to tune the radio to get as strong a signal as I can get.. Then fire up the digital modes software and check out the waterfall.. How much bandwidth is the signal using? Is it taking up 50 or 60 hz? Or is it spread out over 200 or 300 hz? Is it a single trace, or is the signal composed of more than one trace?
Then, I reference the website page that has all the audio samples to find something that sounds similar and a waterfall that looks somewhat the same. From there, I try to match the protocol with the bandwidth..

What am I missing? It must be something but I'm not getting anywhere.

I wish a ham with an Icom 746 transceiver like yours would chime in and help us out here. I'm going to download the manual and also check out any Icom 746 threads that talk about digital signal reception. My first question would be what MODE is your receiver in when receiving these signals? Data transmissions on my transceiver are received on DIGITAL UPPER (upper sideband) regardless of band.

In your next post, when you reference a signal that you are trying to decode, tell us exactly what frequency you are on and what mode you have the transceiver set to.

By the time you post again, I hope to have had time to see what your manual has to say about receiving digital signals. I'll also post any links I find to posts that discuss setting your transceiver up to receive a digital signal.

Hang in there. When I first got started in the digital realm, it took me some time before I could identify a signal and easily decode the signal with the right settings in the software and on my transceiver. But you WILL succeed! Just don't give up!

73, Dave K4EET
 

K4EET

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I'm using an ICOM746 hooked to a laptop through a USB sound card.

For several nights now, I've been trying to decode various digital signals on the 40 meter band..

I'm using FLDigi and starting to get a handle on the controls.. My problem is that with the exception of a few successful CW attempts, I'm not having much luck.

<snip>

A couple of questions...
  1. You have an Icom 746; not the Icom 746 PRO - right?
  2. What Data Modem are you using; SignalLink, RigBlaster, etc.?
  3. Do you know what your Sound Card's Manufacturer and Model Number is?
Also, if you could give us a wiring diagram of how you have everything wired up would be beneficial too. You may not have the hookup quite correct. I want to start from the beginning and work through everything to be sure we are not overlooking something obvious.

Looking forward to your response.

73, Dave K4EET
 

Murphy625

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I just have a 3.5mm jack cable going from the ICOM 746 (non pro) to an External USB Sound Card LINE IN jack.

I had my first breakthroughs today!

This evening, using MultiPSK set to BPSK31, I was able to decode a signal I found at around 9pm.. something about the activity of the sun... sun spots and solar wind or something. The signal came in rather well and the message was easy to read.

Then again at around midnight, I found another BPSK31 signal and was able to decode it also.. this time it was some guy talking about his fishing trip.. but I was only able to decode one side of the conversation.

My radio has SSB and a button for CW and RTTY (forward and reverse).. But every time I hear data signals coming in, they seem much stronger in the lower side band on 40 meters.. Usually around 7.1xx Mhz and up.. When I hear morse code and go to the CW function on the radio, the signal degrades quickly. Heck, sometimes I'm not even sure if I'm on the correct frequency.. I just wiggle around were the signal seems strongest and set it there.

I'm spending a lot of time on Youtube right now learning.. Seems to be a very steep curve to decoding anything beyond CW..

Because I'm not transmitting, I'm not using any of the Signalink or Rig blaster gizmos. And my USB Sound card is just a $12 ebay special:
https://www.ebay.com/itm/USB-5-1-Ch...m=232771329837&_trksid=p2047675.c100005.m1851

The next time I dig into the radio, I'll see if I can maybe record the signal and post it.. Can I do that here? Will the forum let up upload a sound file?

I'm beginning to wonder if my real problem is noise.. I was watching youtube and some of these guys have their waterfall's almost entirely blacked out with just the signal showing. Not sure if that's the result of how they set their decoder interface or how they set the filters on their radios.. My waterfall is all static.. but the signals seem strong themselves.

Oh, and one other thing.. The BPSK31 waterfall signal didn't look anything like what was shown on this website:
DigitalModes
In fact, it didn't really look like any of them listed there...
 

AK9R

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If you are trying to decode signals with a sound card and fldigi, then the radio should be set for upper sideband (USB) all the time. Do not change it. Then use the tuning knob and the tuning adjustment on fldigi's waterfall display to narrow in on the signal.

When you switch to CW or RTTY on the radio, you are dramatically narrowing the bandwidth of the audio signal coming from the radio. On CW, your bandwidth will be around 1 kHz and it will be centered around 700 Hz. CW signals are very narrow, so the radio adjusts these parameters to make it easier for CW operators to copy in their heads. On RTTY, your bandwidth will also be around 1 kHz and it will be centered around 2100 Hz. This is because most RTTY is sent at 2125 Hz with a shift of 170 Hz. By comparison, if you leave the radio on USB, the bandwidth will be 2.4 to 3.0 kHz and will be centered around 1200-1500 Hz. fldigi can work with this and let you see all of the signals that might exist within that bandwidth. Then, you use the tools in fldigi to select the signal you want to decode.

For example, if you want to decode BPSK31 signals on the 20m band, set the radio to 20m USB and tune to 14.070 MHz. Then, look at your fldigi waterfall. Depending on propagation and the time of day, you should see several BPSK31 streams on the waterfall. Click on one of them to see if you can decode it.
 
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