FT8 Operating Frequency


Michael WA7SKG
 

Something I just noticed. I fire up the rig, launch WSJT-X on FT8 and start calling CQ. My dial is set (by WSJT-X) to 14.074.00, my TX Frequency is set in WSJT-X to 1175 Hz with Hold TX Freq checked.

After calling CQ for a while and maybe making a couple contacts, I bring up PSKReporter to see how I am doing. Happily, I see dozens of little balloons with reception reports of my signal. Curiously, however, no two of them show the same operating frequency. I would have expected 14.075.175, but I see everything all over like 14.075.169, 14.077.269, 14.075.172, 14.075.126, etc.

Just curious on this disparity. Probably just something I am not understanding on how FT8works.

--
73,
Michael WA7SKG

"Any day you do not learn one new thing is a wasted day."


Dave Garber
 

Guessing it depends on who is receiving and reporting.   They may be off frequency by a couple of Hz...    

sent by my LG phone

On Thu, Jul 9, 2020, 3:04 PM Michael WA7SKG, <wa7skg@...> wrote:
Something I just noticed. I fire up the rig, launch WSJT-X on FT8 and
start calling CQ. My dial is set (by WSJT-X) to 14.074.00, my TX
Frequency is set in WSJT-X to 1175 Hz with Hold TX Freq checked.

After calling CQ for a while and maybe making a couple contacts, I bring
up PSKReporter to see how I am doing. Happily, I see dozens of little
balloons with reception reports of my signal. Curiously, however, no two
of them show the same operating frequency. I would have expected
14.075.175, but I see everything all over like 14.075.169, 14.077.269,
14.075.172, 14.075.126, etc.

Just curious on this disparity. Probably just something I am not
understanding on how FT8works.

--
73,
Michael WA7SKG

"Any day you do not learn one new thing is a wasted day."


d_ziolkowski
 



Vfo freq plus audio freq

Dan kc2sta


On Thu, Jul 9, 2020, 15:13 Dave Garber <ve3wej@...> wrote:
Guessing it depends on who is receiving and reporting.   They may be off frequency by a couple of Hz...    

sent by my LG phone

On Thu, Jul 9, 2020, 3:04 PM Michael WA7SKG, <wa7skg@...> wrote:
Something I just noticed. I fire up the rig, launch WSJT-X on FT8 and
start calling CQ. My dial is set (by WSJT-X) to 14.074.00, my TX
Frequency is set in WSJT-X to 1175 Hz with Hold TX Freq checked.

After calling CQ for a while and maybe making a couple contacts, I bring
up PSKReporter to see how I am doing. Happily, I see dozens of little
balloons with reception reports of my signal. Curiously, however, no two
of them show the same operating frequency. I would have expected
14.075.175, but I see everything all over like 14.075.169, 14.077.269,
14.075.172, 14.075.126, etc.

Just curious on this disparity. Probably just something I am not
understanding on how FT8works.

--
73,
Michael WA7SKG

"Any day you do not learn one new thing is a wasted day."



Kai-KE4PT
 

Hi Michael,
Those differences may be due to the various stations, including yours, being slightly off frequencies, perhaps due to local oscillator (LO) errors or drift (yours too), or the operators set the dial frequency off (like for the 14.077.269). This has NO effect on the decoding, as long as the short term stability of your LO is okay.
Kai, KE4PT

On 7/9/2020 15:04, Michael WA7SKG wrote:
I would have expected 14.075.175, but I see everything all over like 14.075.169, 14.077.269, 14.075.172, 14.075.126, etc.


Mike Rhodes / W8DN
 

Wonder if it might be because some are using CAT and some are using Fake-It ???

Mike / W8DN

On 7/9/2020 4:43 PM, Kai-KE4PT wrote:
Hi Michael,
Those differences may be due to the various stations, including yours, being slightly off frequencies, perhaps due to local oscillator (LO) errors or drift (yours too), or the operators set the dial frequency off (like for the 14.077.269). This has NO effect on the decoding, as long as the short term stability of your LO is okay.
Kai, KE4PT

On 7/9/2020 15:04, Michael WA7SKG wrote:
I would have expected 14.075.175, but I see everything all over like 14.075.169, 14.077.269, 14.075.172, 14.075.126, etc.



    


Gary - AG0N
 

On Jul 9, 2020, at 13:04, Michael WA7SKG <wa7skg@wa7skg.com> wrote:

Just curious on this disparity. Probably just something I am not understanding on how FT8works.
I’d question the calibration of the reporting stations.

Gary - AG0N


Gary - AG0N
 

On Jul 9, 2020, at 19:08, Gary - AG0N <mcduffie@ag0n.net> wrote:



On Jul 9, 2020, at 13:04, Michael WA7SKG <wa7skg@wa7skg.com> wrote:

Just curious on this disparity. Probably just something I am not understanding on how FT8works.
I’d question the calibration of the reporting stations.
Or yours, of course. How’s your comparison to WWV?

Gary - AG0N


Jim Brown
 

There seems to be a fundamental misunderstanding about how WSJT modes like FT8 are transmitted. They are NOT on the dial frequency, they are on the dial frequency PLUS the audio frequency. For example, if the audio frequency is 1500 Hz, the signal is at 14075.5 kHz. If the audio frequency is 1600 Hz, the signal is at 14075.6 kHz. And so on.

WSJT modes are transmitted as upper sideband modulation, and the computer generates the modulated tone stream. If, for example, you were to listen to the FT8 window in CW mode with a relatively narrow IF, you would hear multiple modulated tone streams as you tuned across the "window." Each signal occupies a small part of the "window," which is really the width of a sideband TX filter.

73, Jim K9YC

On 7/9/2020 1:43 PM, Kai-KE4PT wrote:
Hi Michael,
Those differences may be due to the various stations, including yours, being slightly off frequencies, perhaps due to local oscillator (LO) errors or drift (yours too), or the operators set the dial frequency off (like for the 14.077.269). This has NO effect on the decoding, as long as the short term stability of your LO is okay.
Kai, KE4PT
On 7/9/2020 15:04, Michael WA7SKG wrote:
I would have expected 14.075.175, but I see everything all over like 14.075.169, 14.077.269, 14.075.172, 14.075.126, etc.


Jim Shorney
 

Pick any random station on PSK Reporter with lots of report blobs and they will be all over the place in frequency, sometimes even on the wrong band or no band. This is a problem at the receivers. The digital equivalent of the guys in tho old curmudgeon's net arguing about who's digital readout is correct (mine of course, all you other guys are wrong!). I consider PSKR a non-calibrated frequency reference. It can get you in the ballpark and that is about the best you can hope for.

73

-Jim
NU0C

On Thu, 9 Jul 2020 19:51:22 -0700
"Jim Brown" <k9yc@audiosystemsgroup.com> wrote:

There seems to be a fundamental misunderstanding about how WSJT modes
like FT8 are transmitted. They are NOT on the dial frequency, they are
on the dial frequency PLUS the audio frequency. For example, if the
audio frequency is 1500 Hz, the signal is at 14075.5 kHz. If the audio
frequency is 1600 Hz, the signal is at 14075.6 kHz. And so on.

WSJT modes are transmitted as upper sideband modulation, and the
computer generates the modulated tone stream. If, for example, you were
to listen to the FT8 window in CW mode with a relatively narrow IF, you
would hear multiple modulated tone streams as you tuned across the
"window." Each signal occupies a small part of the "window," which is
really the width of a sideband TX filter.

73, Jim K9YC

On 7/9/2020 1:43 PM, Kai-KE4PT wrote:
Hi Michael,
Those differences may be due to the various stations, including yours,
being slightly off frequencies, perhaps due to local oscillator (LO)
errors or drift (yours too), or the operators set the dial frequency off
(like for the 14.077.269). This has NO effect on the decoding, as long
as the short term stability of your LO is okay.
Kai, KE4PT

On 7/9/2020 15:04, Michael WA7SKG wrote:
I would have expected 14.075.175, but I see everything all over like
14.075.169, 14.077.269, 14.075.172, 14.075.126, etc.



Ted
 

Another possibility, I just recently had an issue and had a local ham do some testing with me. He was seeing me on different Freqs every time I transmitted. After some experimentation we discovered, I using HRD to control the IC-7300 had a problem where HRD sometimes put radio in USB-D, and other times put the radio in USB. When transmitting in USB, my microphone was open and changed my tx freq all over the place. After correcting the program, my tx freq was very stable. 

All the above comments are probably correct but there may be other reasons why an FT8 tx freq isn’t as stable as it should be. 

Let me apologize to each and every ham that I may have caused qrm to without knowing I was doing it. Problem is fixed and is now
 history. 

Ted W4YJC

On Fri, Jul 10, 2020 at 01:07 Jim Shorney <jshorney@...> wrote:

Pick any random station on PSK Reporter with lots of report blobs and they will be all over the place in frequency, sometimes even on the wrong band or no band. This is a problem at the receivers. The digital equivalent of the guys in tho old curmudgeon's net arguing about who's digital readout is correct (mine of course, all you other guys are wrong!). I consider PSKR a non-calibrated frequency reference. It can get you in the ballpark and that is about the best you can hope for.

73

-Jim
NU0C

On Thu, 9 Jul 2020 19:51:22 -0700
"Jim Brown" <k9yc@...> wrote:

> There seems to be a fundamental misunderstanding about how WSJT modes
> like FT8 are transmitted. They are NOT on the dial frequency, they are
> on the dial frequency PLUS the audio frequency. For example, if the
> audio frequency is 1500 Hz, the signal is at 14075.5 kHz. If the audio
> frequency is 1600 Hz, the signal is at 14075.6 kHz. And so on.
>
> WSJT modes are transmitted as upper sideband modulation, and the
> computer generates the modulated tone stream. If, for example, you were
> to listen to the FT8 window in CW mode with a relatively narrow IF, you
> would hear multiple modulated tone streams as you tuned across the
> "window." Each signal occupies a small part of the "window," which is
> really the width of a sideband TX filter.
>
> 73, Jim K9YC
>
> On 7/9/2020 1:43 PM, Kai-KE4PT wrote:
> > Hi Michael,
> > Those differences may be due to the various stations, including yours,
> > being slightly off frequencies, perhaps due to local oscillator (LO)
> > errors or drift (yours too), or the operators set the dial frequency off
> > (like for the 14.077.269). This has NO effect on the decoding, as long
> > as the short term stability of your LO is okay.
> > Kai, KE4PT
> >
> > On 7/9/2020 15:04, Michael WA7SKG wrote: 
> >> I would have expected 14.075.175, but I see everything all over like
> >> 14.075.169, 14.077.269, 14.075.172, 14.075.126, etc. 
> >
> >
> >
> >   
>


--
Ted Wirick  
zebra30@...