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Author Topic: Finding the DX TX freq on FT8  (Read 4439 times)
KD7HNN
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Posts: 60




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« on: October 24, 2017, 10:30:54 PM »

I see guys calling DX stations split on various frequencies, but how do I find where he is transmitting? Obviously if I can hear him he would show up in my band activity screen, but when it's weak long haul DX he might not, but If I can listen on his TX freq I would get a deeper decode and possibly copy him, no?
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AA2UK
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Posts: 312




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« Reply #1 on: October 25, 2017, 07:22:44 AM »

To answer your question knowing the stations T freq doesn't help you decode in anyway with FT8.
If you see others calling him and if your antenna is directional I'd try pointing at him 1st.
Otherwise the same station you're trying to work decodes the entire bandwidth as well.
73, AA2UK
Bill
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KD7HNN
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« Reply #2 on: October 25, 2017, 07:44:53 AM »

To answer your question knowing the stations T freq doesn't help you decode in anyway with FT8.
If you see others calling him and if your antenna is directional I'd try pointing at him 1st.
Otherwise the same station you're trying to work decodes the entire bandwidth as well.
73, AA2UK
Bill

True, BUT, my understanding is that WSJT does a deeper decode on your rx freq than on the entire segment, which could be enough for me to copy him. Obviously I wouldn't just blindly call him without first hearing him.
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AA2UK
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« Reply #3 on: October 25, 2017, 07:57:54 AM »

I don't know where you got that idea?
I've never heard of that and it shouldn't be confused with enable AP.
Bill
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KD7HNN
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« Reply #4 on: October 25, 2017, 08:19:55 AM »

I don't know where you got that idea?
I've never heard of that and it shouldn't be confused with enable AP.
Bill

I got it from the WSJT operating manual section 6.6

ZL2IFB - "Don’t worry too much about your receive frequency: you can safely ignore the dead green goalpost above the waterfall, leaving WSJT-X to move it around for you. The software is decoding the entire waterfall, all at once, right? Well, yes and no: it focuses on the current receive frequency, decoding first and more deeply there. So you might want to set the receive frequency manually if you are monitoring some juicy DX, waiting for him to complete QSOs so you know when to call. On a busy band, the band activity screen scrolls too fast to ‘read the mail’, whereas the Rx Frequency pane scrolls at a far more sedate pace. Very weak traces may be decoded better if you click them on the waterfall to move the green bar there."
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W1VT
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« Reply #5 on: October 25, 2017, 08:41:36 AM »

Sometimes I can see traces of the DX signal on the waterfall that won't decode.
There are usually stations precisely on the DX station's frequency. 

Zack W1VT
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K0UA
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Posts: 1380




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« Reply #6 on: October 25, 2017, 08:48:14 AM »

In my experience there is no difference in the decode ability whether you are clicked on the actual frequency or not.  I have seen plenty of -24 decodes in the left hand pane on FT8.  I don't see any difference.
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NT6X
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« Reply #7 on: October 25, 2017, 09:32:15 AM »

I've definitely seen a difference. The other day I saw guys working C93PA. I never saw him on the left screen, so I frantically tuned the segment looking at every weak trace I could see. I finally found him. He was -21 so I found a clear tx freq and worked him. He never did show up on the left screen but I copied him for 30 minutes on the right screen.

I also monitored a WSPR freq recently. I saw several really weak traces off my rx freq that I couldn't decode. Once I zero beat them, Bam! solid decode.

I think the OP has a valid question.
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K0UA
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« Reply #8 on: October 25, 2017, 10:08:36 AM »

I've definitely seen a difference. The other day I saw guys working C93PA. I never saw him on the left screen, so I frantically tuned the segment looking at every weak trace I could see. I finally found him. He was -21 so I found a clear tx freq and worked him. He never did show up on the left screen but I copied him for 30 minutes on the right screen.

I also monitored a WSPR freq recently. I saw several really weak traces off my rx freq that I couldn't decode. Once I zero beat them, Bam! solid decode.

I think the OP has a valid question.

Maybe so, but I still have seen plenty of -24 decodes in the left pane, and on FT8, I have never seen anything decode at less than -24.  But it is possible I guess.
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AA2UK
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« Reply #9 on: October 25, 2017, 11:32:30 AM »

I'd like to know what version of WSJTX of the stations reporting enhanced decoding of FT8 by double clicking of weak signals on the wide graph.
I'm running 1.8.0-rc3 revision 8183
Here are the latest release notes from Joe Taylor for 1.8.0-rc3
http://physics.princeton.edu/pulsar/k1jt/Release_Notes_1.8.0.txt
Bill, AA2UK
« Last Edit: October 25, 2017, 11:44:07 AM by AA2UK » Logged
AA2UK
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Posts: 312




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« Reply #10 on: October 25, 2017, 02:54:35 PM »

Running FT8 In Deep and enable AP will buy you an additional -4db.
Here are the recent release notes when using AP.
This is an interesting read.......
https://sourceforge.net/p/wsjt/wsjt/8183/tree//branches/wsjtx/doc/user_guide/en/decoder_notes.adoc
Bill, AA2UK
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AA4PB
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« Reply #11 on: October 25, 2017, 03:20:35 PM »

I asked the question on the WSJT group. The answer I got was that FT8 does indeed do more advanced decoding at or near the Rx frequency, making better use of the available computer processing time. In addition, it decodes near that frequency first in order to provide quicker availability of the QSO data. If you have AP selected then there will be an even better processing of the QSO data when decoded at the Rx frequency.

Given the comment regarding computer processing time I suspect that perhaps slower computers or computers that have other programs running may see more of an improvement by decoding on the Rx frequency.

That reinforces my view that you are better off to call on the CQer's Tx frequency unless you have a specific reason to suspect that there may be many stations calling him on that same frequency. It's really no different than the decision to work split on SSB.
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Bob  AA4PB
Garrisonville, VA
ND6M
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Posts: 555




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« Reply #12 on: October 25, 2017, 04:00:02 PM »

... edit... FT8 does indeed do more advanced decoding at or near the Rx frequency, making better use of the available computer processing time. In addition, it decodes near that frequency first in order to provide quicker availability of the QSO data...

Correct, every released version of WSJT places "priority" (K1JT's term) on Rx signals at or near the Tx freq.  about 4 dB can be gained by listening (and calling) there.

So much for workin "split" as the end all for working DX. Sometimes it better, sometimes it's not.

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K0UA
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Posts: 1380




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« Reply #13 on: October 25, 2017, 04:52:39 PM »

I learned something today... thanks.. !

73 James
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VA3VF
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Posts: 816




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« Reply #14 on: October 25, 2017, 07:46:02 PM »

True, BUT, my understanding is that WSJT does a deeper decode on your rx freq than on the entire segment, which could be enough for me to copy him. Obviously I wouldn't just blindly call him without first hearing him.

I think it was the case with the JT65-HF version, and its derivative by HB9HQX. It may also be the case with JTDX. I don't know if it applies to WSJT-X FT8.

As for the other part of your question, if you don't hear the DX, it does not make any difference to you that others are calling the DX everywhere in the segment. Once you hear the DX, then you select an open spot, and call him/her too.
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