Topics

Airspy Mini calibrate #hardware


Dave C aka Dave3825us
 

Can anyone who calibrated their airspy please post directions? Unitrunker has been sounding like crap lately and I ran sdr# on some of the 800MHz freqs and it seems to be off. At 162.475, it seems dead on. On 477.8875 it seems dead on. When getting into the 700's, its not dead on.

Any help or advise would be greatly appreciated.

Thanks


David J Taylor
 

From: Dave C aka Dave3825us via Groups.Io

Can anyone who calibrated their airspy please post directions? Unitrunker has been sounding like crap lately and I ran sdr# on some of the 800MHz freqs and it seems to be off. At 162.475, it seems dead on. On 477.8875 it seems dead on. When getting into the 700's, its not dead on.

Any help or advise would be greatly appreciated.

Thanks
===================================

Dave,

Have you used the calibration program you can download? What reference frequency do you have available? Perhaps get a GPS-locked one such as:

http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=301

Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv


prog
 

On Wed, Nov 15, 2017 at 03:54 am, David J Taylor wrote:
From: Dave C aka Dave3825us via Groups.Io

Can anyone who calibrated their airspy please post directions? Unitrunker has been sounding like crap lately and I ran sdr# on some of the 800MHz freqs and it seems to be off. At 162.475, it seems dead on. On 477.8875 it seems dead on. When getting into the 700's, its not dead on.

Any help or advise would be greatly appreciated.

Thanks
===================================

Dave,

Have you used the calibration program you can download? What reference frequency do you have available? Perhaps get a GPS-locked one such as:

http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=301

Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@...
Twitter:@gm8arv
Before attempting any recalibration, make sure your system doesn't drop samples.


Dave C aka Dave3825us
 

   After dongle was on for 2 hours, this is what she puts out.


David J Taylor
 

From: Dave C aka Dave3825us via Groups.Io

After dongle was on for 2 hours, this is what she puts out.
============================

Looks good to me, Dave. I recall there being an average at the bottom, though.

Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv


Dave C aka Dave3825us
 



Lol.  I knew I forgot something.



Dave C aka Dave3825us
 

For what its worth I get the same results on my laptop also. Fine in the lower but starts to wander in the 500mhz and up. Can my mini be defective?


prog
 

On Mon, Nov 20, 2017 at 08:24 am, Dave C aka Dave3825us wrote:
For what its worth I get the same results on my laptop also. Fine in the lower but starts to wander in the 500mhz and up. Can my mini be defective?
What frequency did you calibrate your unit at? And what is the source signal?


jdow
 

On 2017-11-20 08:33, prog wrote:
On Mon, Nov 20, 2017 at 08:24 am, Dave C aka Dave3825us wrote:
For what its worth I get the same results on my laptop also. Fine in the
lower but starts to wander in the 500mhz and up. Can my mini be defective?
What frequency did you calibrate your unit at? And what is the source signal?
In the US GSM signals are about the only relatively easy signals to use for calibration. The rtlsdr.com website has some articles about it. Aside from GPS any other signal you find is going to be at best "modestly accurate" by NTIA and FCC regulations. Even FM broadcast has a rather large frequency tolerance. Also note that the rtlsdr dongle DLLs adjust frequency to plus or minus 1 ppm. That means at 500 MHz you will be within 500 Hz of correct. Then note that the cheapest rtlsdr dongles have floor sweepings as their frequency control crystals. They can require considerably adjustment to get them on frequency using the "ppm" setting. The rtlsdr dongles are not precision instruments. They are, however, amazing for what you can get for a very nominal price.

{^_^}


Joe M.
 

ATSC pilot signals are very accurate, too, correct?
They are on very specific odd frequencies, though.

Nearly anyone should have access to one or more of those.

Joe M.

On 11/20/2017 4:58 PM, jdow wrote:
On 2017-11-20 08:33, prog wrote:
On Mon, Nov 20, 2017 at 08:24 am, Dave C aka Dave3825us wrote:

For what its worth I get the same results on my laptop also. Fine
in the
lower but starts to wander in the 500mhz and up. Can my mini be
defective?

What frequency did you calibrate your unit at? And what is the source
signal?
In the US GSM signals are about the only relatively easy signals to use
for calibration. The rtlsdr.com website has some articles about it.
Aside from GPS any other signal you find is going to be at best
"modestly accurate" by NTIA and FCC regulations. Even FM broadcast has a
rather large frequency tolerance. Also note that the rtlsdr dongle DLLs
adjust frequency to plus or minus 1 ppm. That means at 500 MHz you will
be within 500 Hz of correct. Then note that the cheapest rtlsdr dongles
have floor sweepings as their frequency control crystals. They can
require considerably adjustment to get them on frequency using the "ppm"
setting. The rtlsdr dongles are not precision instruments. They are,
however, amazing for what you can get for a very nominal price.

{^_^}



---
This email has been checked for viruses by AVG.
http://www.avg.com


Dave C aka Dave3825us
 

It was 462.something. I used a cobra walkie talkie . Tried from 5 feet away to 1 foot away. Get like 3.xx something ppm, then -1.04 ppm and after 4 or 5 tries its now at 0.06. 


Airspy US
 

Are you aware that the ppm display is not showing the ppm error, but the delta of the oscillator to get to 0 ppm error? You don't want to get it as close to 0 as possible - you want it to be the correct factor for the unit which is virtually never "0".

Also, the accuracy of the Cobra HT is far worse than the accuracy of the Airspy units, so your HT likely threw the calibration off - perhaps by as much as 5 ppm.

You should only calibrate it to an accurate source. That means *no* HTs. In fact, no mobiles or bases either.

If the unit came from us, it was calibrated to a GPS clock before shipment and should not need recalibrated. Doing so would make it less accurate unless calibrated to a source of similar accuracy.

---------
Airspy.US
Your USA source for quality SDR products!
www.Airspy.US

NOTE! This email address is not routinely monitored.
If you have an issue, please contact us at airspy@airspy.us

On 11/21/2017 8:47 AM, Dave C aka Dave3825us via Groups.Io wrote:
It was 462.something. I used a cobra walkie talkie . Tried from 5 feet away to 1 foot away. Get like 3.xx something ppm, then -1.04 ppm and after 4 or 5 tries its now at 0.06.


Denny
 

As Joe mentioned, yes the modern DTV pilot carriers are very accurate and widely available in the US. Here is a link that in great detail describes the pilot carrier frequencies used, including co-channel issues that at that time were of concern:   . http://earthsignals.com/add_CGC/RF_Column_77_Jul_98.pdf

Denny - K0LGI -


prog
 
Edited

On Tue, Nov 21, 2017 at 05:47 am, Dave C aka Dave3825us wrote:
It was 462.something. I used a cobra walkie talkie . Tried from 5 feet away to 1 foot away. Get like 3.xx something ppm, then -1.04 ppm and after 4 or 5 tries its now at 0.06. 
Do you really believe a cobra walkie talkie is a good source for stable carrier? The signal is *frequency* modulated in function of your ambient audio. ie. completely random. Plus even without modulation, these talkies have worse frequency accuracy and stability than the Airspies.
I suggest you send it to Joe at airspy.us for proper calibration.


jdow
 

There is a suggestion on the web that the pilot carriers for US DTV are worth using. I tuned one earlier to day on a GPS stabilized AirSpy R1 and figure they are good for 1ppm level, at least. I am not sure what the digits beyond the XXX.310 MHz should be I saw about 400 Hz low. But that may be that the correct frequency really is slightly below XXX.310 MHz. At the very least it is more accurate than most cheap handheld equipment.

{^_^}

On 2017-11-21 12:32, prog wrote:
[Edited Message Follows]
On Tue, Nov 21, 2017 at 05:47 am, Dave C aka Dave3825us wrote:
It was 462.something. I used a cobra walkie talkie . Tried from 5 feet away
to 1 foot away. Get like 3.xx something ppm, then -1.04 ppm and after 4 or 5
tries its now at 0.06. Do you really believe a cobra walkie talkie is a good source for stable carrier? The signal is **frequency** modulated in function of your ambient audio. ie. completely random. Plus even without modulation, these talkies have worse frequency accuracy and stability than the Airspies.
I suggest you send it to Joe at airspy.us for proper calibration.


Airspy US
 

From the lower edge of the channel the standard ATSC pilot is at 309.440559 kHz.

So, if the lower edge of the channel is 500 MHz, the pilot would be at 500.309440559 MHz, and no you cannot tune with that accuracy in any SDR program AFAWK, but even if you tune to 500.309441 MHz you would be within 1 Hz.

Obviously with a specification in the milliHertz class, the accuracy would have to be very tight. This will not yield GPS accuracy, but is the best free source for the general public.

---------
Airspy.US
Your USA source for quality SDR products!
www.Airspy.US

NOTE! This email address is not routinely monitored.
If you have an issue, please contact us at airspy@airspy.us

On 11/22/2017 3:10 AM, jdow wrote:
There is a suggestion on the web that the pilot carriers for US DTV are worth using. I tuned one earlier to day on a GPS stabilized AirSpy R1 and figure they are good for 1ppm level, at least. I am not sure what the digits beyond the XXX.310 MHz should be I saw about 400 Hz low. But that may be that the correct frequency really is slightly below XXX.310 MHz. At the very least it is more accurate than most cheap handheld equipment.

{^_^}

On 2017-11-21 12:32, prog wrote:
[Edited Message Follows]

On Tue, Nov 21, 2017 at 05:47 am, Dave C aka Dave3825us wrote:

It was 462.something. I used a cobra walkie talkie . Tried from 5 feet away
to 1 foot away. Get like 3.xx something ppm, then -1.04 ppm and after 4 or 5
tries its now at 0.06.
Do you really believe a cobra walkie talkie is a good source for stable carrier? The signal is **frequency** modulated in function of your ambient audio. ie. completely random. Plus even without modulation, these talkies have worse frequency accuracy and stability than the Airspies.
I suggest you send it to Joe at airspy.us for proper calibration.



---
This email has been checked for viruses by AVG.
http://www.avg.com


jdow
 

Um, lemme see, 1 Hz at 500 MHz is about 2 ppb. That's plenty accurate for most people's calibration needs. I don't think the SDRSharp/AirSpy allow ppt tuning adjustments.

Thanks for saving me the time to look up the exact number. That correlates very nicely with what I was seeing. (And the fan on my motherboard's IO Hub (5520)chip gave up the ghost and the heatsink's plastic mounting tabs melted off. I had to rig up a risky substitute arrangement. SIGH!)

{^_-}

On 2017-11-22 00:46, Airspy US via Groups.Io wrote:
From the lower edge of the channel the standard ATSC pilot is at 309.440559 kHz.
So, if the lower edge of the channel is 500 MHz, the pilot would be at 500.309440559 MHz, and no you cannot tune with that accuracy in any SDR program AFAWK, but even if you tune to 500.309441 MHz you would be within 1 Hz.
Obviously with a specification in the milliHertz class, the accuracy would have to be very tight. This will not yield GPS accuracy, but is the best free source for the general public.
---------
Airspy.US
Your USA source for quality SDR products!
www.Airspy.US
NOTE! This email address is not routinely monitored.
If you have an issue, please contact us at airspy@airspy.us
On 11/22/2017 3:10 AM, jdow wrote:
There is a suggestion on the web that the pilot carriers for US DTV are worth using. I tuned one earlier to day on a GPS stabilized AirSpy R1 and figure they are good for 1ppm level, at least. I am not sure what the digits beyond the XXX.310 MHz should be I saw about 400 Hz low. But that may be that the correct frequency really is slightly below XXX.310 MHz. At the very least it is more accurate than most cheap handheld equipment.

{^_^}

On 2017-11-21 12:32, prog wrote:
[Edited Message Follows]

On Tue, Nov 21, 2017 at 05:47 am, Dave C aka Dave3825us wrote:

    It was 462.something. I used a cobra walkie talkie . Tried from 5 feet away
    to 1 foot away. Get like 3.xx something ppm, then -1.04 ppm and after 4 or 5
    tries its now at 0.06.
Do you really believe a cobra walkie talkie is a good source for stable carrier? The signal is **frequency** modulated in function of your ambient audio. ie. completely random. Plus even without modulation, these talkies have worse frequency accuracy and stability than the Airspies.
I suggest you send it to Joe at airspy.us for proper calibration.




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This email has been checked for viruses by AVG.
http://www.avg.com


Chris Spacone <cspacone@...>
 

I think the larger takeaway might be at least two fold, and probably many more fold:

1 - Don't mess with something that is working.
2 - Understand the thing you are messing with.

Where 'mess' is replaced with a four letter Anglo-Saxon derivative many of us old Navy guys are familiar with...

-Chris


---- jdow <jdow@earthlink.net> wrote:

There is a suggestion on the web that the pilot carriers for US DTV are worth
using. I tuned one earlier to day on a GPS stabilized AirSpy R1 and figure they
are good for 1ppm level, at least. I am not sure what the digits beyond the
XXX.310 MHz should be I saw about 400 Hz low. But that may be that the correct
frequency really is slightly below XXX.310 MHz. At the very least it is more
accurate than most cheap handheld equipment.

{^_^}

On 2017-11-21 12:32, prog wrote:
[Edited Message Follows]

On Tue, Nov 21, 2017 at 05:47 am, Dave C aka Dave3825us wrote:

It was 462.something. I used a cobra walkie talkie . Tried from 5 feet away
to 1 foot away. Get like 3.xx something ppm, then -1.04 ppm and after 4 or 5
tries its now at 0.06.

Do you really believe a cobra walkie talkie is a good source for stable carrier?
The signal is **frequency** modulated in function of your ambient audio. ie.
completely random. Plus even without modulation, these talkies have worse
frequency accuracy and stability than the Airspies.
I suggest you send it to Joe at airspy.us for proper calibration.



Shirley Dulcey KE1L
 

The required frequency accuracy for TV broadcasters is 500 Hz. That's
a bit better than 1ppm for stations in the UHF band. The worst case is
low VHF stations, where it can be in the 5-10ppm range.

NOAA weather broadcasts are another useful reference. They're supposed
to be accurate to 1.5ppm. The standards for AM and FM radio
broadcasters are much looser.

Some broadcasters pride themselves on technical excellence and
considerably exceed the minimum requirements. Here in Boston, for
example, you should be able to get a very accurate reference by using
WGBH. Big network stations are likely to be more accurate than second
and third tier broadcasters. SDR# only lets you set the correction in
increments of 1ppm in any case, so there are limits to how accurately
you can set your receiver.

On Wed, Nov 22, 2017 at 11:25 AM, Chris Spacone <cspacone@socal.rr.com> wrote:
I think the larger takeaway might be at least two fold, and probably many more fold:

1 - Don't mess with something that is working.
2 - Understand the thing you are messing with.

Where 'mess' is replaced with a four letter Anglo-Saxon derivative many of us old Navy guys are familiar with...

-Chris


---- jdow <jdow@earthlink.net> wrote:
There is a suggestion on the web that the pilot carriers for US DTV are worth
using. I tuned one earlier to day on a GPS stabilized AirSpy R1 and figure they
are good for 1ppm level, at least. I am not sure what the digits beyond the
XXX.310 MHz should be I saw about 400 Hz low. But that may be that the correct
frequency really is slightly below XXX.310 MHz. At the very least it is more
accurate than most cheap handheld equipment.

{^_^}

On 2017-11-21 12:32, prog wrote:
[Edited Message Follows]

On Tue, Nov 21, 2017 at 05:47 am, Dave C aka Dave3825us wrote:

It was 462.something. I used a cobra walkie talkie . Tried from 5 feet away
to 1 foot away. Get like 3.xx something ppm, then -1.04 ppm and after 4 or 5
tries its now at 0.06.

Do you really believe a cobra walkie talkie is a good source for stable carrier?
The signal is **frequency** modulated in function of your ambient audio. ie.
completely random. Plus even without modulation, these talkies have worse
frequency accuracy and stability than the Airspies.
I suggest you send it to Joe at airspy.us for proper calibration.





jdow
 

Hm, I'll have to get the real rules and take a look. Some documentation I found from about the period of the transition away from NTSC is that the DTV stations had to have very precise frequency control RELATIVE to adjacent channel NTSC transmitters. They were required to be within something like 3 Hz. With the ubiquity of GPS locked standards these days any decent size station should have precise frequency control with the possibility of (precisely) 10 kHz offsets to minimize co-channel interference. The FCC rules are a serious maze. And no enforcement happens unless somebody who knows the rules notices an error and complains. Then the FCC "might" act.
{^_^}

On 2017-11-22 08:49, Shirley Dulcey KE1L wrote:
The required frequency accuracy for TV broadcasters is 500 Hz. That's
a bit better than 1ppm for stations in the UHF band. The worst case is
low VHF stations, where it can be in the 5-10ppm range.
NOAA weather broadcasts are another useful reference. They're supposed
to be accurate to 1.5ppm. The standards for AM and FM radio
broadcasters are much looser.
Some broadcasters pride themselves on technical excellence and
considerably exceed the minimum requirements. Here in Boston, for
example, you should be able to get a very accurate reference by using
WGBH. Big network stations are likely to be more accurate than second
and third tier broadcasters. SDR# only lets you set the correction in
increments of 1ppm in any case, so there are limits to how accurately
you can set your receiver.
On Wed, Nov 22, 2017 at 11:25 AM, Chris Spacone <cspacone@socal.rr.com> wrote:
I think the larger takeaway might be at least two fold, and probably many more fold:

1 - Don't mess with something that is working.
2 - Understand the thing you are messing with.

Where 'mess' is replaced with a four letter Anglo-Saxon derivative many of us old Navy guys are familiar with...

-Chris


---- jdow <jdow@earthlink.net> wrote:
There is a suggestion on the web that the pilot carriers for US DTV are worth
using. I tuned one earlier to day on a GPS stabilized AirSpy R1 and figure they
are good for 1ppm level, at least. I am not sure what the digits beyond the
XXX.310 MHz should be I saw about 400 Hz low. But that may be that the correct
frequency really is slightly below XXX.310 MHz. At the very least it is more
accurate than most cheap handheld equipment.

{^_^}

On 2017-11-21 12:32, prog wrote:
[Edited Message Follows]

On Tue, Nov 21, 2017 at 05:47 am, Dave C aka Dave3825us wrote:

It was 462.something. I used a cobra walkie talkie . Tried from 5 feet away
to 1 foot away. Get like 3.xx something ppm, then -1.04 ppm and after 4 or 5
tries its now at 0.06.

Do you really believe a cobra walkie talkie is a good source for stable carrier?
The signal is **frequency** modulated in function of your ambient audio. ie.
completely random. Plus even without modulation, these talkies have worse
frequency accuracy and stability than the Airspies.
I suggest you send it to Joe at airspy.us for proper calibration.