Date   

Re: My Computer Drifts!

David J Taylor
 

In the previous, swap 02 ms for 0.2 ms, and click rate for clock rate!
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@...
Twitter: @gm8arv


Re: My Computer Drifts!

David J Taylor
 

On 04/06/2022 20:03, jdow wrote:
My configuration here involves a Linux router that does a lot of other work and
a largish set of PCs around the house, mostly here in the computer room. They
range from PLCs to a rather hypertrophied gaming machine use for multiple VMs,
development, and the like. (Visual Studio is THE preeminent game in the known
universe.)

When speaking of accuracy you have to deal with a pot load of different entry
points for errors. The ones NTP monitors and considers in its design are delay,
offset, and jitter. NTP, as embodied in the canonical Univ of U of Delaware
version as amended up to date, measures the path delay in such a way as to get
a reasonable estimate of path delays to multiple sources. The path to and the
path from the server may be slightly different. You can see that in the offset
value. NTP makes a best estimate for time and publishes the time offsets. It
also passes this information along to the consumers. Offset here varies from
-5.3ms to 5.9ms. The chosen clock and the secondary are coming in at + and - 2
ms. The chosen clock is .NIST.. The secondary clock is .GPS. I could setup a
pure GPS configuration here if I hooked up the PPS from my Trimble to the
router. But, it's not broke so I don't fix it. The final figure, jitter, gives
a good estimate of the link quality between the consumer and the hosts. The two
good ones are coming in at under 6 ms of jitter. All these numbers vary with
time of day. For my current needs this is good enough. If I needed better I'd
have to go to a formal PPS hookup. (None of the USB crap, either. They do look
like fun to play with, though.)

For my main PC I am using a very old tool I have had for a long time. Mr.
Horsley created an open sores partial implementation of ntp that I use to tweak
my PC's clock in 1ms steps - since at least early XP days through today. I have
it logging clock corrections. Most are 0 ms with the occasional 1ms correction.
I ran Symmetricom's ntp for awhile. But I went back to Tom's tool. It ain't
broke and I have a much older view on the urgency to make perfect than I used
to have.

(I am one of the persons responsible for the GPS phase 2B satellite segment's
extremely accurate intentional inaccuracy for whatever worth that may be.)

If ntp accuracy is insufficient at least one more protocol exists that refines
to microseconds or finer. It is/was used by radio astronomers to get them in
the ballpark.

{^_^}
Certainly tying the PPS into the router would increase performance. Typically
here I see up to 02 ms jitter from the internal servers, and under 2 ms from
the pool servers (UK). They all show an offset of 2-3 ms, but this with a
cable modem link that's 200 Mbps down, 20 Mbps up, hence gross asymmetry.

During the development of Windows NTP (by Dave Hart) I used to monitor much
more that I do now. The offset graphs are enough.

As you know, reference NTP alters the click rate rather than stepping the
clock. Since Windows 8.1 NTP uses the more accurate time instructions which
are in 100 nanosecond units, and this has improved things a lot.

Thanks for contributing to the Selective Availability work - perhaps one of the
factors which led to the Galileo constellation which has meant more satellites
for everyone!

Cheers,
David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@...
Twitter: @gm8arv


Re: My Computer Drifts!

David J Taylor
 

On 04/06/2022 20:21, jdow wrote:
Um, just a quibble here, the three pool entries I also use are never chosen as the reference. Of necessity one of them is always one of the candidates. But, then, I am a very modest number of hops from the .NIST. and .GPS. servers on the list. Pool servers almost always have much larger delay times. NIST is 46 ms. The best pool entry I have is 83 ms and the worst is about 120 ms. So NIST is not particularly bad to use. The other one is a local large university's engineering department.
{^_^}
That's just what I mean by well-configured. You can adjust things to suit your own local requirements. My chosen server is always one of my own stratum-1 servers. My UK or NL pool servers are typically between 19 and 43 ms away, perhaps you might do better by US state rather than just US?

For most folk, just using the local pool servers will be fine.

Cheers,
David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@...
Twitter: @gm8arv


SDR's For Sale, ETC.V2 Hi Hi.

John
 



John P Bain.

Begin forwarded message:

From: John Bain <johnpbain@...>
Date: 4 June 2022 at 18:47:56 BST
To: dennis.fitch@...
Subject: Re: SDR's For Sale, ETC.V2 Hi Hi.


Hi Dennis, I think I paid about £230 from Martin Lynch. I'm looking for £150 plus postage. As you know its a very small device about 10 cm by 6 cm and also very light. I will upgrade the firmware if you want as its on an old version. 
 Hope the info helps. Very Best Wishes and Very Best Regards to you and your Family Dennis. 
 73 John. MM3UMZ. 
 Here's a couple of pictures 


STAY SAFE AND STAY HEALTHY. 

On Sat, 4 Jun 2022 at 16:55, Dennis Fitch <dennis.fitch@...> wrote:
Hi John, could be interested in the HF+, can you give me a price, thanks.



Regards

Dennis Fitch  MIPS  G8IMN

**All emails & attachments scanned by Kaspersky 2022**


--
John Bain


Re: My Computer Drifts!

jdow
 

On 20220604 06:54:58, David J Taylor via groups.io wrote:
On 04/06/2022 11:02, Dirk wrote:
David,
thank you! You mainly confirm what I wrote.
I use a GPS module with PPS output and a RS232 converter, PPS connected to a
serial handshake line.
Of course my PC has a real (hardware) RS232 interface.

Yes, the problem these days is getting that "bit level" input to the PC.  For
my most recent purchase I made sure to specify a motherboard which had at least
the COM port header.

I agree with Conrad that for most purposes a properly configured NTP is quite
sufficient, but folk still think that the overloaded NIST servers in the US are
the best things to use, rather than something more local where the "pool"
directive (UK, DE, NL etc.) will help NTP automatically find the best.

Cheers,
David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@...
Twitter: @gm8arv

Um, just a quibble here, the three pool entries I also use are never chosen as the reference. Of necessity one of them is always one of the candidates. But, then, I am a very modest number of hops from the .NIST. and .GPS. servers on the list. Pool servers almost always have much larger delay times. NIST is 46 ms. The best pool entry I have is 83 ms and the worst is about 120 ms. So NIST is not particularly bad to use. The other one is a local large university's engineering department.

{^_^}


Re: My Computer Drifts!

jdow
 

Is your PPS signal reception based on a signal that instantly raises a VERY high priority interrupt? And how does your software account for the interrupt latency? Does it also account for the delays inherent in reading the clock? And are you far enough gone into the weeds that you post process results with the published corrections? I'm kind of wondering how far out into the accuracy weeds an aficionado might go. I know my level of silliness in the70s. I disciplined a precision crystal oscillator into the single digit ppb or less using WWV over months of very careful tweeking. If my station was going to have a crystal calibrator by goofy it was going to be as accurate as I could make it.

{^_-}    Joanne (Yes, I very probably DO have Aspergers syndrome.)

On 20220604 03:02:13, Dirk wrote:

David,
thank you! You mainly confirme what I wrote.
I use a GPS module with PPS output and a RS232 converter, PPS connected to a serial handshake line.
Of course my PC has a real (hardware) RS232 interface.


Re: My Computer Drifts!

jdow
 

On 20220604 02:25:26, David J Taylor via groups.io wrote:
On 04/06/2022 08:31, Dirk wrote:
David, talking about GPS:
With NTP alone you can reach a time deviation in the lower millisecond range.
Using only the GPS time information you CAN reach a time deviation also in the
low double-digit millisecond range, if GPS hardware and software can be told to
decode only ONE NMEA sentence.
With GPS alone or with NTP plus GPS you CAN reach a time deviation in the
microsecond range, using certain GPS hardware.
If you e.g. read the Meinberg documentation, the use of the GPS *PPS signal* is
described in detail. With the PPS signal the beginning of each second can be
detected.

Dirk,

I think may Linux users would be disappointed to get low milliseconds from NTP
- and Windows makes it much more difficult (although better with Windows 8 and
later).  The problem with GPS alone is that while you may get a low deviation,
that deviation is referenced to other than UTC - certainly having a single NMEA
sentence and high baud rate can help.  I've seen differences in excess of a second!

GPS alone is not good enough for microsecond deviation, you must have PPS as
well.  A GPS over USB, for example, does not typically have a PPS signal, and
even if it does it subject to the USB polling rate (125 microseconds).

Getting good results can depend on pot luck, to a degree, as different network
cards and drivers influence the results.  Just for interest:

Windows stratum-1 PPS-synced PCs:
  https://www.satsignal.eu/mrtg/performance_ntp.php#windows-stratum-1

Windows (& Linux) synced over the LAN from stratum-1 servers
  https://www.satsignal.eu/mrtg/performance_ntp.php#windows

Cheers,
David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@...
Twitter: @gm8arv


My configuration here involves a Linux router that does a lot of other work and a largish set of PCs around the house, mostly here in the computer room. They range from PLCs to a rather hypertrophied gaming machine use for multiple VMs, development, and the like. (Visual Studio is THE preeminent game in the known universe.)

When speaking of accuracy you have to deal with a pot load of different entry points for errors. The ones NTP monitors and considers in its design are delay, offset, and jitter. NTP, as embodied in the canonical Univ of U of Delaware version as amended up to date, measures the path delay in such a way as to get a reasonable estimate of path delays to multiple sources. The path to and the path from the server may be slightly different. You can see that in the offset value. NTP makes a best estimate for time and publishes the time offsets. It also passes this information along to the consumers. Offset here varies from -5.3ms to 5.9ms. The chosen clock and the secondary are coming in at + and - 2 ms. The chosen clock is .NIST.. The secondary clock is .GPS. I could setup a pure GPS configuration here if I hooked up the PPS from my Trimble to the router. But, it's not broke so I don't fix it. The final figure, jitter, gives a good estimate of the link quality between the consumer and the hosts. The two good ones are coming in at under 6 ms of jitter. All these numbers vary with time of day. For my current needs this is good enough. If I needed better I'd have to go to a formal PPS hookup. (None of the USB crap, either. They do look like fun to play with, though.)

For my main PC I am using a very old tool I have had for a long time. Mr. Horsley created an open sores partial implementation of ntp that I use to tweak my PC's clock in 1ms steps - since at least early XP days through today. I have it logging clock corrections. Most are 0 ms with the occasional 1ms correction. I ran Symmetricom's ntp for awhile. But I went back to Tom's tool. It ain't broke and I have a much older view on the urgency to make perfect than I used to have.

(I am one of the persons responsible for the GPS phase 2B satellite segment's extremely accurate intentional inaccuracy for whatever worth that may be.)

If ntp accuracy is insufficient at least one more protocol exists that refines to microseconds or finer. It is/was used by radio astronomers to get them in the ballpark.

{^_^}


Simon's World Map 1.2.10

Simon Brown
 

Simon's World Map 1.2.10 available, added support for the Geomagnetic Dst Index.

https://g4eli.com/world-map
Software. This is a rewrite of a previous project, this program: Uses DirectX / Direct2D graphics. Requires minimal CPU power, will run on any Windows 7 / 8 / 10 system
g4eli.com


--
- + - + -
Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Re: SDR's For Sale, ETC.V2 Hi Hi.

John
 

Anybody interested in the hermes lite 2 or the afedri sdr (pictures in an earlier post, I also have an airspy hf+ dual port (not discovery), an mfj 1026 deluxe noise cancelling/signal enhancing(basically just a phasing unit for 2 antennas) can be used with a transceiver it has transmit sense for bypassing it on transmit. 

Anybody interested in buying any of the stuff I've mentioned please contact me. I have other unused radio equipment in the spare room, all radio gear is boxed and as new. 

For attention of Andrea I think I should have shipping information for the wellbrook loop by around Tuesday/Wednesday, I have been searching for a good deal on shipping and think my wife will have it sorted by midweek at the very latest but more than likely it will be before Wednesday. I'll contact you as soon as I have definite information. 
 
 Very Best Wishes and Very Best Regards to All. 

73.  John. 
 STAY SAFE AND STAY HEALTHY. 
 

On Sat, 4 Jun 2022 at 01:50, John Bain via groups.io <johnpbain=gmail.com@groups.io> wrote:
Hi Sigi, 

Apologies for messaging you out of the blue, but I haven't had a chance to ask you yet if you were interested in the Hermes Lite 2 I mentioned in the group.

After doing the sums and converting from dollars to pounds I think its cost me between about £290/£310 plus the shipping cost, with exchange rates being all over the place thats probably something like $360/$395 dollars and between about €335/€360 euros. 
 
 I'm not looking to make crazy money on my Hermes Lite 2 like I know that some of the guys in various groups are doing Sigi. You have probably seen it in some of the groups where they have popped up in groups at over a hundred dollars more than the cost of a new one from makerfabs. 

I am only asking or looking to get the same amount of money that I paid for it. Its a standard Hermes Lite 2 with the N2ADR filter board fitted and in the standard 40mm enclosure. Using it with Simon's sdr console side by side with my icom ic-7300 and on the same antenna I'd honestly say it is every bit as good as my icom and a couple of times using Simon's software it pulled a couple of signals out of the noise that my icom was struggling with. 

Anyway Sigi, Apologies again for messaging you out of the blue and sorry to trouble you. If you're interested in the Hermes just let me know and if not just let me know that as well if you want. 

 As I've said probably too many times, I'm not looking at selling the radio for crazy profit like some guys are. I'm just looking to get back what I paid for it and with the crazy way exchange rates are its anywhere between £290/£310 pounds but I think probably £300 or something in that area is what I paid. Awk I honestly don't know. I'm only selling it to help pay for another radio, well the Hermes the Afedri, the Airspy HF+ dual port, and some other radio stuff that I don't need or maybe just don't use or have any use for now, there's even an MFJ 1026 Deluxe Noise Cancelling unit. Think its just really a phasing unit.

 No doubt I'll eventually fund my next radio, hopefully it'll even be before it goes out of production, hi-hi. 



Sorry to trouble you Sigi. 
Very Best Wishes and Very Best Regards to you and your Family Sigi. 73 John. 

Sorry to Simon and the group for this kinda long message and still not with any great sales pitch from me either. 
STAY SAFE AND STAY HEALTHY. 

On Thu, 2 Jun 2022 at 09:53, Siegfried Jackstien <siegfried.jackstien@...> wrote:

me too

;-)

dg9bfc sigi

Am 02.06.2022 um 06:46 schrieb mathews ember:
I would be interested in that Hermes lite.
How much you asking for it

--
John Bain

--
John Bain


Re: My Computer Drifts!

David J Taylor
 

On 04/06/2022 11:02, Dirk wrote:
David,
thank you! You mainly confirm what I wrote.
I use a GPS module with PPS output and a RS232 converter, PPS connected to a
serial handshake line.
Of course my PC has a real (hardware) RS232 interface.
Yes, the problem these days is getting that "bit level" input to the PC. For
my most recent purchase I made sure to specify a motherboard which had at least
the COM port header.

I agree with Conrad that for most purposes a properly configured NTP is quite
sufficient, but folk still think that the overloaded NIST servers in the US are
the best things to use, rather than something more local where the "pool"
directive (UK, DE, NL etc.) will help NTP automatically find the best.

Cheers,
David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@...
Twitter: @gm8arv


Re: Satellite tracking is not tracking.

Simon Brown
 

Hi,

Just show a screenshot of the main satellite tracking window please. Also show me your TLE settings as below.



From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of David Coles via groups.io <g7gzc@...>
Sent: 04 June 2022 11:48
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: [SDR-Radio] Satellite tracking is not tracking.
 
Can I delete all Keplers and start over again?
If so, how so please?
Receiving NOAA Wx sats on entered frequencies is a joy.
73 Dave G7GZC

--
- + - + -
Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Re: My Computer Drifts!

Conrad, PA5Y
 

If I recall correctly, Simon just wanted to correct a drifting PC clock using his existing hardware. Probably as a reference for recording or maybe decoding with one of the many digital modes in common use. I don't recall him expressing any interest in becoming a time nut 😊

 

My pragmatic approach is that Meinberg NTP server provides adequate performance for both scenarios without adding any hardware. It also serves me well for my EME operating.

 

So, I will stick with that, and I suspect most users will do the same.

 

However, it is an interesting topic.

 

Regards

 

Conrad PA5Y

 

 

 

 

 

-----Original Message-----
From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of David J Taylor via groups.io
Sent: 04 June 2022 11:25
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] My Computer Drifts!

 

On 04/06/2022 08:31, Dirk wrote:

> David, talking about GPS:

> With NTP alone you can reach a time deviation in the lower millisecond range.

> Using only the GPS time information you CAN reach a time deviation

> also in the low double-digit millisecond range, if GPS hardware and

> software can be told to decode only ONE NMEA sentence.

> With GPS alone or with NTP plus GPS you CAN reach a time deviation in

> the microsecond range, using certain GPS hardware.

> If you e.g. read the Meinberg documentation, the use of the GPS *PPS

> signal* is described in detail. With the PPS signal the beginning of

> each second can be detected.

 

Dirk,

 

I think may Linux users would be disappointed to get low milliseconds from NTP

- and Windows makes it much more difficult (although better with Windows 8 and later).  The problem with GPS alone is that while you may get a low deviation, that deviation is referenced to other than UTC - certainly having a single NMEA sentence and high baud rate can help.  I've seen differences in excess of a second!

 

GPS alone is not good enough for microsecond deviation, you must have PPS as well.  A GPS over USB, for example, does not typically have a PPS signal, and even if it does it subject to the USB polling rate (125 microseconds).

 

Getting good results can depend on pot luck, to a degree, as different network cards and drivers influence the results.  Just for interest:

 

Windows stratum-1 PPS-synced PCs:

   https://www.satsignal.eu/mrtg/performance_ntp.php#windows-stratum-1

 

Windows (& Linux) synced over the LAN from stratum-1 servers

   https://www.satsignal.eu/mrtg/performance_ntp.php#windows

 

Cheers,

David

--

SatSignal Software - Quality software for you

Web: https://www.satsignal.eu

Email: david-taylor@...

Twitter: @gm8arv

 

 

 

 


Satellite tracking is not tracking.

David Coles
 

Can I delete all Keplers and start over again?
If so, how so please?
Receiving NOAA Wx sats on entered frequencies is a joy.
73 Dave G7GZC


Re: My Computer Drifts!

Dirk
 
Edited

David,
thank you! You mainly confirm what I wrote.
I use a GPS module with PPS output and a RS232 converter, PPS connected to a serial handshake line.
Of course my PC has a real (hardware) RS232 interface.


Re: My Computer Drifts!

David J Taylor
 

On 04/06/2022 08:31, Dirk wrote:
David, talking about GPS:
With NTP alone you can reach a time deviation in the lower millisecond range.
Using only the GPS time information you CAN reach a time deviation also in the
low double-digit millisecond range, if GPS hardware and software can be told to
decode only ONE NMEA sentence.
With GPS alone or with NTP plus GPS you CAN reach a time deviation in the
microsecond range, using certain GPS hardware.
If you e.g. read the Meinberg documentation, the use of the GPS *PPS signal* is
described in detail. With the PPS signal the beginning of each second can be
detected.
Dirk,

I think may Linux users would be disappointed to get low milliseconds from NTP
- and Windows makes it much more difficult (although better with Windows 8 and
later). The problem with GPS alone is that while you may get a low deviation,
that deviation is referenced to other than UTC - certainly having a single NMEA
sentence and high baud rate can help. I've seen differences in excess of a second!

GPS alone is not good enough for microsecond deviation, you must have PPS as
well. A GPS over USB, for example, does not typically have a PPS signal, and
even if it does it subject to the USB polling rate (125 microseconds).

Getting good results can depend on pot luck, to a degree, as different network
cards and drivers influence the results. Just for interest:

Windows stratum-1 PPS-synced PCs:
https://www.satsignal.eu/mrtg/performance_ntp.php#windows-stratum-1

Windows (& Linux) synced over the LAN from stratum-1 servers
https://www.satsignal.eu/mrtg/performance_ntp.php#windows

Cheers,
David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@...
Twitter: @gm8arv


Re: World Map 1.2.9

Simon Brown
 

So,

Running a test - if it correctly picks up the next value change I'll make 1.3.10 available today.


From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of Simon Brown via groups.io <simon@...>
Sent: 04 June 2022 08:33
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: Re: [SDR-Radio] World Map 1.2.9
 
So,

Seems to work, see attachment.

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of Simon Brown via groups.io <simon@...>
Sent: 03 June 2022 23:05
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: Re: [SDR-Radio] World Map 1.2.9
 
OK, looks quite easy. Will take a look tomorrow morning.

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of Cormac, EI4HQ via groups.io <ei4hq.mail@...>
Sent: 03 June 2022 22:11
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: Re: [SDR-Radio] World Map 1.2.9
 
Hi Simon,

Thanks for v1.2.9, in particular for adding bearing & distance display for stations, a very useful feature addition. I use World Map a lot for Navtex DX activities as it provides a neat way to display pretty much all that's needed; the stations, time, terminator and space weather data. I maintain a Navtex station data suite for the Navtex DX community and I've been including World Map 490 and 518 Navtex station files as part of it for a while now.

A feature request if I could be so forward; any chance you might consider adding the real time Dst index to the propagation info. provided; https://wdc.kugi.kyoto-u.ac.jp/dst_realtime/presentmonth/index.html? It's a useful propagation pointer for those of us who DX below 1MHz (NDBs, Navtex, MW & LW broadcasting, that sort of thing). When the Dst spikes upwards, that can be an early warning of a subsequent drop/plunge into -ve Dst figures that often means MW propagation is in trouble. The deeper the dive into -ve territory, the more trouble we're in. On the other hand, all other things being equal a relatively stable Dst hovering around zero is generally a good thing for <1MHz propagation.

Thanks!

--
- + - + -
Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.

--
- + - + -
Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.

--
- + - + -
Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Re: World Map 1.2.9

Simon Brown
 

So,

Seems to work, see attachment.


From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of Simon Brown via groups.io <simon@...>
Sent: 03 June 2022 23:05
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: Re: [SDR-Radio] World Map 1.2.9
 
OK, looks quite easy. Will take a look tomorrow morning.

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of Cormac, EI4HQ via groups.io <ei4hq.mail@...>
Sent: 03 June 2022 22:11
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: Re: [SDR-Radio] World Map 1.2.9
 
Hi Simon,

Thanks for v1.2.9, in particular for adding bearing & distance display for stations, a very useful feature addition. I use World Map a lot for Navtex DX activities as it provides a neat way to display pretty much all that's needed; the stations, time, terminator and space weather data. I maintain a Navtex station data suite for the Navtex DX community and I've been including World Map 490 and 518 Navtex station files as part of it for a while now.

A feature request if I could be so forward; any chance you might consider adding the real time Dst index to the propagation info. provided; https://wdc.kugi.kyoto-u.ac.jp/dst_realtime/presentmonth/index.html? It's a useful propagation pointer for those of us who DX below 1MHz (NDBs, Navtex, MW & LW broadcasting, that sort of thing). When the Dst spikes upwards, that can be an early warning of a subsequent drop/plunge into -ve Dst figures that often means MW propagation is in trouble. The deeper the dive into -ve territory, the more trouble we're in. On the other hand, all other things being equal a relatively stable Dst hovering around zero is generally a good thing for <1MHz propagation.

Thanks!

--
- + - + -
Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.

--
- + - + -
Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Re: My Computer Drifts!

Dirk
 

David, talking about GPS:
With NTP alone you can reach a time deviation in the lower millisecond range.
Using only the GPS time information you CAN reach a time deviation also in the low double-digit millisecond range, if GPS hardware and software can be told to decode only ONE NMEA sentence.
With GPS alone or with NTP plus GPS you CAN reach a time deviation in the microsecond range, using certain GPS hardware.
If you e.g. read the Meinberg documentation, the use of the GPS PPS signal is described in detail. With the PPS signal the beginning of each second can be detected.


Re: My Computer Drifts!

jdow
 

Do you know how NTP works or only think you know?

{o.o}   Just askin'

On 20220603 13:07:06, BobS via groups.io wrote:

But I'm not talkng about NTP. My point is still valid. Using a GPS is trivial and it suffers from far less latency compared to NTP.


Re: My Computer Drifts!

David J Taylor
 

On 03/06/2022 21:07, BobS via groups.io wrote:
But I'm not talkng about NTP. My point is still valid. Using a GPS is trivial
and it suffers from far less latency compared to NTP.
Bob,

You need to be careful about your choice of servers for any timekeeping
software. Don't use servers a continent away, and try to use the "best" server
available to you. Reference NTP and the pool servers do all this automatically.

The typical GPS does not output UTC, but a variable length serial message, so
you won't be syncing your PC to UTC but something hundreds of milliseconds
later than UTC. Better than nothing, yes, but...

Best, if you can, take out that Raspberry Pi you left in the drawer years back
and add a simple GPS/PPS device to it, run reference NTP, and you'll have
something much, much better than either Internet-based servers or a serial-only
GPS.

Cheers,
David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@...
Twitter: @gm8arv

1521 - 1540 of 67993