Date
1 - 20 of 21
GPSDO Kiwi frequency accuracy
Rob Robinett
As we further refine the use of the Kiwi, at KFS I have been comparing frequencies and spreading reported by Bodnar-fed Kiwis with frequencies reported by standard GPS-aided Kiwis at KFS and nearby WD sites.
That investigation led me to realize that the .1 Hz frequency correction added by default to spot frequencies reported by a GPS-aided Kiwi should not be applied to GPSDO (e.g. Bodnar) Kiwis fed with 66.660000 Mhz. So if you are using a Kiwi modified to use an external GPSDO, set it to 66.6600, enter that value on the Kiwi's Admin->Config-> External clock frequency field, and suppress WD's correction by adding this line to your WD.conf file:
That investigation led me to realize that the .1 Hz frequency correction added by default to spot frequencies reported by a GPS-aided Kiwi should not be applied to GPSDO (e.g. Bodnar) Kiwis fed with 66.660000 Mhz. So if you are using a Kiwi modified to use an external GPSDO, set it to 66.6600, enter that value on the Kiwi's Admin->Config-> External clock frequency field, and suppress WD's correction by adding this line to your WD.conf file:
SPOT_FREQ_ADJ_HZ=+0.0
As reported in other threads on this forum. a standard GPS-aided Kiwi is accurate to better than .1 Hz on 20M, and spreading appears to be worse than a GSPDO Kiwi by only 30-50 mHz. So as long as your Kiwi reports 8+ good satellites on its Admon->GPS page, I don't see much need for a GPSDO.
I think it is truly remarkable that the standard Kiwi is so frequency accurate and as a result so useful in radio science studies.
I think it is truly remarkable that the standard Kiwi is so frequency accurate and as a result so useful in radio science studies.
Glenn Elmore
I'm a little unclear about the precise frequency hard coded ito the Kiwi. I've been using 66.66 MHz as that number though I've recently seen some cause for thinking it may acturally be 66.666 or 66.666666 MHz. The difference between that and 66.66 MHz has little effect in the baseband offset being corrected but maybe somebody here can tell me/us what the 'real' number for zero offset is. Maybe just an academic question.
On 11/15/22 11:28, Rob Robinett wrote:
As we further refine the use of the Kiwi, at KFS I have been comparing frequencies and spreading reported by Bodnar-fed Kiwis with frequencies reported by standard GPS-aided Kiwis at KFS and nearby WD sites.
That investigation led me to realize that the .1 Hz frequency correction added by default to spot frequencies reported by a GPS-aided Kiwi should not be applied to GPSDO (e.g. Bodnar) Kiwis fed with 66.660000 Mhz. So if you are using a Kiwi modified to use an external GPSDO, set it to 66.6600, enter that value on the Kiwi's Admin->Config-> External clock frequency field, and suppress WD's correction by adding this line to your WD.conf file:
SPOT_FREQ_ADJ_HZ=+0.0
As reported in other threads on this forum. a standard GPS-aided Kiwi is accurate to better than .1 Hz on 20M, and spreading appears to be worse than a GSPDO Kiwi by only 30-50 mHz. So as long as your Kiwi reports 8+ good satellites on its Admon->GPS page, I don't see much need for a GPSDO.
I think it is truly remarkable that the standard Kiwi is so frequency accurate and as a result so useful in radio science studies.
Gwyn Griffiths
Hello Rob
Having added the line to my wsprdaemon.conf:
SPOT_FREQ_ADJ_HZ=+0.0
I then realised that it applies to all of the receivers that wd handles. Here it handles one Kiwi with a mini-Bodnar and one standard aided (primarily so I can monitor the behaviour of both clock sources), and so, in my case, a global value is unfortunately not appropriate? In mixed cases like mine, does the value need to be set for each receiver named in the list in the conf file?
regards and thanks as always
Gwyn G3ZIL
Having added the line to my wsprdaemon.conf:
SPOT_FREQ_ADJ_HZ=+0.0
I then realised that it applies to all of the receivers that wd handles. Here it handles one Kiwi with a mini-Bodnar and one standard aided (primarily so I can monitor the behaviour of both clock sources), and so, in my case, a global value is unfortunately not appropriate? In mixed cases like mine, does the value need to be set for each receiver named in the list in the conf file?
regards and thanks as always
Gwyn G3ZIL
Rob Robinett
I have the same condition at KFS where only 2 of the 6 Kiwis are fed by the Bodnar.
So I have checked in code which allows one to configure WD to selectively suppress frequency adjustments.
To do so, add a line like this to your conf file.
GPS_KIWIS="KIWI_Omni_C KIWI_Omni_D" ### At KFS these Kiwis are driven by a 66.66 MHz Bodnar, so they don't need frequency connection
I have also added a description of the use of GPS_KIWIS to wd_template.conf to the descriptions of how to use other such 'hidden' configuration variables:
### At WD sites which have a mixture of standard GPS-aided Kiwis which require 0.1 Hz to be added to spot frequencies, and GPSDO-fed Kiwis which
### report accurate spots frequencies and thus doen't require that adjustment, one can suppress the application of SPOT_FREQ_ADJ_HZ by adding
### those GPSDO Kiwis to this space-separated list
# GPS_KIWIS="KIWI_1 KIWI_2" ### Change these to the name(s) you have given your Kiwis
### report accurate spots frequencies and thus doen't require that adjustment, one can suppress the application of SPOT_FREQ_ADJ_HZ by adding
### those GPSDO Kiwis to this space-separated list
# GPS_KIWIS="KIWI_1 KIWI_2" ### Change these to the name(s) you have given your Kiwis
On Wed, Nov 16, 2022 at 1:00 AM Gwyn Griffiths via groups.io <gxgriffiths=virginmedia.com@groups.io> wrote:
Hello Rob
Having added the line to my wsprdaemon.conf:
SPOT_FREQ_ADJ_HZ=+0.0
I then realised that it applies to all of the receivers that wd handles. Here it handles one Kiwi with a mini-Bodnar and one standard aided (primarily so I can monitor the behaviour of both clock sources), and so, in my case, a global value is unfortunately not appropriate? In mixed cases like mine, does the value need to be set for each receiver named in the list in the conf file?
regards and thanks as always
Gwyn G3ZIL
--
Glenn Elmore
I defer to Gwyn here but I think the baseband processing has 66.66 MHz hardcoded into its processing and does not use whatever value the user enters for the External ADC clock and the rest of the Kiwi. Thus the RF frequency can be moved around (over/under clocking is possible) but a baseband offset will be introduced if that external clock is not 66.66 MHz. I think that offsert amounts to about 1.4 Hz if/when the external clock and its setting is 66.60 rather than 66.66 MHz. But I may be wrong about this...
On 11/16/22 09:48, Erwin - PE3ES -
F4VTQ via groups.io wrote:
Does this mean the info on the Kiwi itself is wrong ?
Set when external 66.666600 MHz (nominal)
clock connected to J5 connector/pad.
External ADC clock?YesNoSet when external 66.666600 MHz (nominal)
clock connected to J5 connector/pad.
Gwyn Griffiths
Glenn's explanation is essentially correct, and is a summary of the explanation set out by John Seamons at
forum.kiwisdr.com/index.php?p=/discussion/comment/14977#Comment_14977
but two of Glenn's numbers are not quite right (the 1.4 Hz should be 0.14 Hz at 1500 Hz baseband frequency, and the 66.60 should be 66.666600).
If you enter 66.666600 MHz as the external clock frequency and set your clock to the same value you will be emulating the nominal crystal clock frequency in the Kiwi itself. The RF section will produce the correct frequency - so the carrier frequency will be correct.
However, the original choice of 66.666600 MHz for the crystal in the Kiwi was an approximation to the required frequency of 66.660000 MHz for the baseband processing to produce audio at an exact rate of 12000 Hz. The difference amounts to 0.14 Hz at 1500 Hz, the centre of interest for this community. This did not matter a hoot when only 1 Hz frequency resolution was available, but with 0.1 Hz resolution available in the wsprdaemon extended spots database, and the improvements since v1.557 in the Kiwi's own GPS-aided frequency stability when used without a browser the difference of 0.14 Hz became visible when compared with a Kiwi using an external clock set to 66.660000 MHz that provides spot-on audio frequencies.
As Rob wrote, the frequency stability of the standard aided Kiwi is now good enough to see phenomena such as the morning fall in the height of the ionosphere by observing the order 1 Hz Doppler shift. Following the advice in this post ensures that there is no offset between standard aided and GPSDO Kiwis thereby helping those investigations.
Gwyn G3ZIL
forum.kiwisdr.com/index.php?p=/discussion/comment/14977#Comment_14977
but two of Glenn's numbers are not quite right (the 1.4 Hz should be 0.14 Hz at 1500 Hz baseband frequency, and the 66.60 should be 66.666600).
If you enter 66.666600 MHz as the external clock frequency and set your clock to the same value you will be emulating the nominal crystal clock frequency in the Kiwi itself. The RF section will produce the correct frequency - so the carrier frequency will be correct.
However, the original choice of 66.666600 MHz for the crystal in the Kiwi was an approximation to the required frequency of 66.660000 MHz for the baseband processing to produce audio at an exact rate of 12000 Hz. The difference amounts to 0.14 Hz at 1500 Hz, the centre of interest for this community. This did not matter a hoot when only 1 Hz frequency resolution was available, but with 0.1 Hz resolution available in the wsprdaemon extended spots database, and the improvements since v1.557 in the Kiwi's own GPS-aided frequency stability when used without a browser the difference of 0.14 Hz became visible when compared with a Kiwi using an external clock set to 66.660000 MHz that provides spot-on audio frequencies.
As Rob wrote, the frequency stability of the standard aided Kiwi is now good enough to see phenomena such as the morning fall in the height of the ionosphere by observing the order 1 Hz Doppler shift. Following the advice in this post ensures that there is no offset between standard aided and GPSDO Kiwis thereby helping those investigations.
Gwyn G3ZIL
Erwin - PE3ES - F4VTQ
I love these clear explanations ! Thank you all.
So look at the below graph, see the 1 Hz jump/drop. My KiwiSDr is now on 66.66 since a day or so, the site of LX1DQ has 4 Kiwi's with slightly different effects compared to my spots. This one has the smallest frequency difference.
Can the 1 Hz morning fall be seen when comparing 2 different stations in this way ? Or is sunshine falling on one of the Kiwi's creating a quick change in the frequency ?
So look at the below graph, see the 1 Hz jump/drop. My KiwiSDr is now on 66.66 since a day or so, the site of LX1DQ has 4 Kiwi's with slightly different effects compared to my spots. This one has the smallest frequency difference.
Can the 1 Hz morning fall be seen when comparing 2 different stations in this way ? Or is sunshine falling on one of the Kiwi's creating a quick change in the frequency ?
Gwyn Griffiths
The remaining small offset in your graph is down to the settings at LX1DQ. If you run the same graph against G3ZIL and receiver G3ZIL_4 that has a mini-Bodnar on 20 m then I am seeing no more than +/-0.1 Hz difference this morning.
As for the morning fall. You can probably see it between two receivers for spots from the same transmitter, but I have not looked at that case yet, just the whole population of spots received at two receivers. I've added a slide with the relevant plots and an extended caption to show the observations so far.
What needs to be done with this example is to turn the Doppler shift of the JA-> California spots into velocity, integrate to get distance, and see if the result is anywhere near the distance the ionosphere has descended in those three hours with the rise then fall in the Doppler.
Gwyn G3ZIL
As for the morning fall. You can probably see it between two receivers for spots from the same transmitter, but I have not looked at that case yet, just the whole population of spots received at two receivers. I've added a slide with the relevant plots and an extended caption to show the observations so far.
What needs to be done with this example is to turn the Doppler shift of the JA-> California spots into velocity, integrate to get distance, and see if the result is anywhere near the distance the ionosphere has descended in those three hours with the rise then fall in the Doppler.
Gwyn G3ZIL
Gwyn Griffiths
Hello Alan
The frequency you are seeing is correct (the '00' being a typo for '0').
From experience, the Kiwi G3ZIL_4 here with the mini-Bodnar external clock, shows the same frequency as the transmit station has entered.
From the 0.1 Hz resolution data in wsprdaemon_spots_s table, the frequencies for OZ0RF here this morning were as below.
Gwyn G3ZIL
The frequency you are seeing is correct (the '00' being a typo for '0').
From experience, the Kiwi G3ZIL_4 here with the mini-Bodnar external clock, shows the same frequency as the transmit station has entered.
From the 0.1 Hz resolution data in wsprdaemon_spots_s table, the frequencies for OZ0RF here this morning were as below.
Gwyn G3ZIL
time | freq
---------------------+------------
2022-11-18 12:25:00 | 14.0971550
2022-11-18 12:15:00 | 14.0971551
2022-11-18 12:05:00 | 14.0971552
2022-11-18 11:55:00 | 14.0971549
2022-11-18 11:45:00 | 14.0971556
2022-11-18 11:35:00 | 14.0971552
2022-11-18 11:25:00 | 14.0971557
2022-11-18 11:15:00 | 14.0971554
2022-11-18 11:05:00 | 14.0971551
2022-11-18 10:55:00 | 14.0971552
2022-11-18 10:45:00 | 14.0971556
2022-11-18 10:35:00 | 14.0971552
2022-11-18 10:25:00 | 14.0971552
2022-11-18 10:15:00 | 14.0971552
2022-11-18 10:05:00 | 14.0971553
2022-11-18 09:55:00 | 14.0971550
2022-11-18 09:25:00 | 14.0971551
2022-11-18 09:15:00 | 14.0971555
2022-11-18 09:05:00 | 14.0971554
2022-11-18 08:55:00 | 14.0971555
2022-11-18 08:45:00 | 14.0971554
Hello
The RFzero WSPR frequency is correct in the library since release 0.8.6 from 2019-12-03. This follows an investigation done by Warren, WA8TOD, and response from Steven, K9AN, forwarding an email from Joe, K1JT, saying in short:
"The case for WSPR is rather different, though. The four tones are closely spaced and have equal weighting. It doesn't make much sense to use one convention for the frequency of received signals (the center of the four tones) and another convention for the transmitted signal (that of the lowest tone). It seems that I should move the transmitted tones lower by 1.5*12000/8192 = 2.197 Hz. I will do so."
However, if FST4W uses the same way, I don't know, but I have implemented it in the same way.
While we speak of RFzero the last of the missing component is to arrive next week. So I am still confident that units will be produced in the beginning of December.
Bo
www.rudius.net/oz2m :: www.rfzero.net
The RFzero WSPR frequency is correct in the library since release 0.8.6 from 2019-12-03. This follows an investigation done by Warren, WA8TOD, and response from Steven, K9AN, forwarding an email from Joe, K1JT, saying in short:
"The case for WSPR is rather different, though. The four tones are closely spaced and have equal weighting. It doesn't make much sense to use one convention for the frequency of received signals (the center of the four tones) and another convention for the transmitted signal (that of the lowest tone). It seems that I should move the transmitted tones lower by 1.5*12000/8192 = 2.197 Hz. I will do so."
However, if FST4W uses the same way, I don't know, but I have implemented it in the same way.
While we speak of RFzero the last of the missing component is to arrive next week. So I am still confident that units will be produced in the beginning of December.
Bo
www.rudius.net/oz2m :: www.rfzero.net
Alan G4ZFQ
On 18/11/2022 12:44, Gwyn Griffiths via groups.io wrote:
Thanks, I was surprised to see the '00'.
I was playing with Spectrum laboratory and my AOR7030 with a cheap u-blox GPS for a marker. Unless I am wrong I see the lowest tone at the frequency that is reported. 14.097155
I'm sorry but I still found Bo's quote of Joe's comment "It seems that I should move the transmitted tones lower" confusing.
I noticed about 0.5 Hz rise from 15.15 to 15.40 on the 17th, not too easy to see when mixed with WSPR. I have not yet found how to access that on the the wsprdaemon database.
I see a gap in reception this morning 06.40-07.40, almost looks as if propagation had continued the shift would have been higher than the 1Hz at 07.45
73 Alan G4ZFQ
The frequency you are seeing is correct (the '00' being a typo for '0').Gwyn, Bo,
Thanks, I was surprised to see the '00'.
I was playing with Spectrum laboratory and my AOR7030 with a cheap u-blox GPS for a marker. Unless I am wrong I see the lowest tone at the frequency that is reported. 14.097155
I'm sorry but I still found Bo's quote of Joe's comment "It seems that I should move the transmitted tones lower" confusing.
I noticed about 0.5 Hz rise from 15.15 to 15.40 on the 17th, not too easy to see when mixed with WSPR. I have not yet found how to access that on the the wsprdaemon database.
I see a gap in reception this morning 06.40-07.40, almost looks as if propagation had continued the shift would have been higher than the 1Hz at 07.45
73 Alan G4ZFQ
The WSPR math/spec is:
tone0 = f - 1,5 * sample rate / samples
tone1 = f - 0,5 * sample rate / samples
tone2 = f + 0,5 * sample rate / samples
tone3 = f + 1,5 * sample rate / samples
e.g. using the same spec for FST4W-300, where the sample rate is 12 kHz and the samples are 21 504:
tone0 = f - 1,5 * 12000 / 21504 = f - 0,837 Hz
for WSPR tone 0 would be = f - 2,197 Hz.
Bo
www.rudius.net/oz2m :: www.rfzero.net
tone0 = f - 1,5 * sample rate / samples
tone1 = f - 0,5 * sample rate / samples
tone2 = f + 0,5 * sample rate / samples
tone3 = f + 1,5 * sample rate / samples
e.g. using the same spec for FST4W-300, where the sample rate is 12 kHz and the samples are 21 504:
tone0 = f - 1,5 * 12000 / 21504 = f - 0,837 Hz
for WSPR tone 0 would be = f - 2,197 Hz.
Bo
www.rudius.net/oz2m :: www.rfzero.net
Gwyn Griffiths
Hello Alan
Please do send me a private email to see if I can help you with what you'd like to get from the database / Grafana.
"I have not yet found how to access that on the the wsprdaemon database".
I could understand Bo's quote from Joe, "It seems that I should move the transmitted tones lower" if there was a typo and 'transmitted' should read 'received'.
Gwyn G3ZIL
Please do send me a private email to see if I can help you with what you'd like to get from the database / Grafana.
"I have not yet found how to access that on the the wsprdaemon database".
I could understand Bo's quote from Joe, "It seems that I should move the transmitted tones lower" if there was a typo and 'transmitted' should read 'received'.
Gwyn G3ZIL
Alan G4ZFQ
On 19/11/2022 12:38, Bo, OZ2M wrote:
I am still confused, quite normal:-)
Can we agree that the normal uploaded frequency from wd is that of the lowest RF frequency transmitted?
14.09755 without any shift?
Gwyn, thanks, I'll be in touch.
73 Alan G4ZFQ
https://sourceforge.net/p/wsjt/mailman/message/34135506/Bo,
I am still confused, quite normal:-)
Can we agree that the normal uploaded frequency from wd is that of the lowest RF frequency transmitted?
14.09755 without any shift?
Gwyn, thanks, I'll be in touch.
73 Alan G4ZFQ