Topics

fldigi and sound card calibration

Mike Stansberry
 

Well, I'm stuck again. I'm trying to do a sound card calibration and what I'm seeing
on screen isn't matching what I read in the on line guide.  The only thing I know
is it "used" to work some years ago.

Any advise?

73, Mike, K0TER

Mike Stansberry
 

On Sat, Jul 4, 2020 at 02:06 PM, Mike Stansberry wrote:
Well, I'm stuck again. I'm trying to do a sound card calibration and what I'm seeing
on screen isn't matching what I read in the on line guide.  The only thing I know
is it "used" to work some years ago.

Any advise?

73, Mike, K0TER

Ed W3NR
 

On 7/6/20 2:27 PM, Mike Stansberry wrote:
On Sat, Jul 4, 2020 at 02:06 PM, Mike Stansberry wrote:
Well, I'm stuck again. I'm trying to do a sound card calibration and what I'm seeing
on screen isn't matching what I read in the on line guide.  The only thing I know
is it "used" to work some years ago.

Any advise?

73, Mike, K0TER
_._,_._,_

Same here, wonder what changed ?

Ed W3NR

Dave
 

WWV @ 10 MHz

What are you seeing that is different ?

David

On 7/6/20 2:49 PM, Ed W3NR wrote:
On 7/6/20 2:27 PM, Mike Stansberry wrote:
On Sat, Jul 4, 2020 at 02:06 PM, Mike Stansberry wrote:
Well, I'm stuck again. I'm trying to do a sound card calibration and what I'm seeing
on screen isn't matching what I read in the on line guide.  The only thing I know
is it "used" to work some years ago.

Any advise?

73, Mike, K0TER

Ed W3NR
 

On 7/6/20 4:13 PM, Dave wrote:

WWV @ 10 MHz

What are you seeing that is different ?

David

Not even close as to what is shown in the manual.

Ed W3NR

Dave
 

K3eui
 

Ed  W3NR

There is the "sound card" calibration itself
And
There is the HF radio's  USB  VFO  calibration.

These are two completely different items. Don't confuse them.
Usually modern sound cards don't need much tweaking (in ppm).

SOUND CARD itself
To check the sound card, there are quite a few ways to do this.
Easy way  -  tune to  WWV  on  AM  mode  (no BFO) on 10 or 15 MHz
Every minute there is either a  500 Hz  tone or a  600 Hz tone. They alternate. You can see how close you are on your waterfall  (expand 4x) to those "standard" audio pitch tones from WWV.  You will see the line of audio either close to  500  Hz  or close to  600 Hz.
Typically a sound card will be within  1 Hz  (or far better).
I've also used a standard  440 Hz musical tuning fork and a mic to check my sound card's accuracy.

You can also do the more elaborate  WWV  Calibration technique which allows you to change the  'sample rate' in FLDIGI.  That takes a few minutes, and some patience.  BTW ... use  native rate.  The instructions are pretty straight forward in the FLDIGI help menus.

=======================================

Radio's  VFO  dial calibration (in USB mode)  -  usually more serious !!
This one is a bit trickier, but can be done in a minute or two.
Tune your radio to  1.000 kHz  below the standard  10 or 15 MHz WWV but be sure your mode is now  Upper Sideband.  So now your VFO dial reads  9999.000  kHz   (9.999000  MHz).  If you were to tune your radio's VFO  right on 10.000  or  15.000 MHz  you would hear a tone at  ZERO Hz, so don't try that.

The  WWV  CARRIER  (at  10 or 15 MHz)  will "beat with your radio's  BFO" and you should see (and hear) a STEADY  tone around 1000 Hz on your FLDIGI Waterfall.  Be sure you are not in LSB  or  CW  mode.
Ignore the beeps now at  1500 Hz or  1600 Hz  caused by the audio tones going ON/OFF.  Listen for the STEADY tone close to 1000 Hz on the FLDIGI waterfall.

Thus, you can see how far your VFO dial calibration is off (in Hz).
If the STEADY tone  (not the beeping sounds) is less than 10 Hz in error  on the AUDIO  waterfall  (990 Hz  or  1010 Hz) it is probably not worth trying to correct your radio's  BFO for upper sideband.   Some of the newer rigs actually have a readout (resolution) to the nearest whole Hz.
And some rigs actually allow you to calibrate the radio's VFO dial internally  (Icom 7610)  by ear using  WWV  standard carrier.

Just make a note of how far above/below 1000 Hz  the VFO dial calibration is from "true".  Or, you can tune the VFO dial to  2.000 kHz below  10 or 15 MHz  (9998.000 kHz) and thus the "beat" note will be at  2000 Hz (audio) on the FLDIGI waterfall.

I wrote up something for QST about sound card and VFO calibration in USB mode which is in the publication line somewhere with more details and screen shots.

GL

Barry  k3eui


On Jul 6, 2020, at 5:00 PM, Ed W3NR <autek@...> wrote:

On 7/6/20 4:13 PM, Dave wrote:

WWV @ 10 MHz

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What are you seeing that is different ?

David

Not even close as to what is shown in the manual.

Ed W3NR