Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1] 2 3 Next   Go Down
  Print  
Author Topic: Can't decode FT8, but can decode JT65 signal  (Read 6230 times)
HS0ZIB
Member

Posts: 598




Ignore
« on: September 16, 2017, 06:06:25 PM »

This is my first attempt to decode an FT8 signal.

I'm running version 1.8.0-rc2 of WSJT-X.  I am receiving a clear FT8 signal on 17 mb.  (I know that it is an FT8 signal because of the 15-second transmit time).

I'm not overrunning the microphone input - I have set input levels at 0dB and in WSJT-X, the input level is always in the green level, at about 35dB.

The signal will not decode!  When the blue decode button flashes just before the end of the 15 seconds, no text is displayed in the text window.

My laptop clock is synchronised using an atomic clock synchronisation application.

If I then tune a few KHz up to a weak JT65 signal, and switch the WSJT-X mode to JT65, the signal is decoded fine!!

What's up?  Why can't I decode the FT-8 signal (or any FT-8 signal, weak or strong, that I've tried)

Any suggestions?  I've tried to reduce the input levels even more, but there is no decode at any level that I've tried.

Logged
K0UA
Member

Posts: 1371




Ignore
« Reply #1 on: September 16, 2017, 06:26:06 PM »

Increase the input level,  Mine runs about 50 to 60 at all times when actually decoding signals.  Resting at about 35 with absolutely no signal.  I suspect you don't enough signal going to the pc.
Logged
HS0ZIB
Member

Posts: 598




Ignore
« Reply #2 on: September 16, 2017, 06:45:31 PM »

I've tried with an increased signal level.  Tested different increases until well into the red.

No decode, nada...

JT65 decode is fine ...
Logged
HS0ZIB
Member

Posts: 598




Ignore
« Reply #3 on: September 16, 2017, 07:36:08 PM »

Wait!  Maybe I have the answer.

From this thread:

http://www.eham.net/ehamforum/smf/index.php/topic,116476.0.html

I read that there is a strange 15-second digital signal on 18102 KHz that is not FT8.  Well, that's the same frequency that I'm receiving this strong 15-second signal.  So maybe I am receiving something that is not FT8......

But the other thread reports that this signal comes from a station in Cuba.  That's the other side of the world from me, seems too strong for that QTH.  So maybe there is someone more local to me (eg Asiatic Russia etc) who has the same problem as the Cuban station.

I will tune around and look for some other 15-second signals and try to decode them as FT8....
Logged
HS0ZIB
Member

Posts: 598




Ignore
« Reply #4 on: September 17, 2017, 03:15:36 AM »

Quote
Wait!  Maybe I have the answer.

Unfortunately, that was not the answer...

I found some more 15-second signals, loud at my QTH.

I can't decode them!  And the JT65 signals can be decoded just fine.

Very frustrating - I can't think what the problem is.  It doesn't endear FT8 to me as an easy mode to decode.
Logged
WB2KSP
Member

Posts: 627




Ignore
« Reply #5 on: September 17, 2017, 04:04:45 AM »

What are you settings?
Logged
AJ8MH
Member

Posts: 253


WWW

Ignore
« Reply #6 on: September 17, 2017, 06:41:14 AM »

You have to be in USB.  I don't think I saw it printed anywhere, but I just tried LSB and couldn't get anything to decode.
Logged
HS0ZIB
Member

Posts: 598




Ignore
« Reply #7 on: September 17, 2017, 06:50:00 AM »

Yes, I'm in USB.

As mentioned, I can't decode FT8, but if I tune 2 KHz up to a JT65 signal and switch to JT65 mode on the software, it decodes fine!

I'm stumped!
Logged
ND6M
Member

Posts: 553




Ignore
« Reply #8 on: September 17, 2017, 07:09:17 AM »

Well, for starters.try deleting the entire WSJT program and then reinstall it.

Good luck
Logged
K0UA
Member

Posts: 1371




Ignore
« Reply #9 on: September 17, 2017, 08:06:26 AM »

Me too..  Yes, try a fresh re install.  Did the older RC1 version decode FT8 for you?  I can't think what this could be, if you can decode JT65 and JT9, then you must have the correct soundcard installed and good connections...  I would have to see this.   Perplexed here in Missouri...
Logged
AJ8MH
Member

Posts: 253


WWW

Ignore
« Reply #10 on: September 17, 2017, 01:15:35 PM »

Is FT-8 timing more critical?  Maybe your clock application isn't working correctly.  Most of the stations I work are within .1 - .4 seconds of my clock.  I'm using Meinberg NTP on 2 computers and it seems to work great.  Had problems with Dimension 4 on one computer, so I changed it out on both.  My sound card is set to DVD quality, but never had a problem with CD quality.

Never used JT65.
Logged
WB2KSP
Member

Posts: 627




Ignore
« Reply #11 on: September 17, 2017, 01:51:37 PM »

Good point. I'm using dimension 4 which is freeware. I have it sync every ten minutes to a local NY server and my clock is always in perfect sync with WWV.
Logged
K0UA
Member

Posts: 1371




Ignore
« Reply #12 on: September 17, 2017, 02:04:00 PM »

I don't think the timing is any more critical. Unfortunately are the only one on the planet having this problem.

How do you feel about posting screen shots (you can use postimage) of all of your settings on WSJT-x.   Let us look them over, and maybe we can come up with something. 
Logged
HS0ZIB
Member

Posts: 598




Ignore
« Reply #13 on: September 17, 2017, 06:20:39 PM »

Quote
Did the older RC1 version decode FT8 for you?

I never used RC1 with FT8.  I decided to download the latest version (RC2) because of all the interest in FT8, and to see what I was 'missing'.  Well, I'm still missing it!

My clock sync program syncs with an external time-server every 5 minutes, so that's not the problem.

I think I'll uninstall the RC2 version, then download RC1 to see if that works.
Logged
K0UA
Member

Posts: 1371




Ignore
« Reply #14 on: September 17, 2017, 07:26:27 PM »

Post some pictures.  Post pictures of the waterfall on 20 meters.  We need to see what is wrong..

What is your radio? what is your interface?  What is your computer.?  What about JT9, can you decode that.  WSPR?  Have you tried to decode WSPR signals?
« Last Edit: September 17, 2017, 07:28:43 PM by K0UA » Logged
Pages: [1] 2 3 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!