[time-nuts] NPL Open House 2018 prepare for 2019

[Bo Hansen]

Hello

This is a very early warning for the 2019 event.

Thursday 17/5 Michael, OZ2ELA, and I attended the NPL Open House 2018 event: 
 Our visit was both to attend the event but 
also to see what NPL uses the Next Generation Beacons units for.

It was a really interesting event with lots of information for those interested 
in "the measure of all things", e.g. the work on the optical clock aiming for a 
1 x 10^-20.

If the above link and the program sounds interesting then look out for the 2019 
event. If you are an international subscriber to this list it is worth a 
travel. NPL is only 10 km from London Heathrow. When the 2019 invitation is 
published I advice you to download the Visitor Guide study it and plan your 
route.

A great thanks to Jochen and Giuseppe!

Bo, OZ2M

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Anyone have experience with this antenna?

[Bo Hansen]

Hi

Indeed a radome may distort the antenna pattern. In teh case of DIY projects 
the trick that most can apply is to take a piece of the radome material and put 
it into a microwave own. If it doesn't get hot it is OK for most DIY cases.

Infinion have some nice GNSS MMICs e.g. BGA924N6 


Bo

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

[time-nuts] Anyone have experience with this antenna?

[Bo Hansen]

Hi

Besides the RF characteristics it may also be worth considering the quality of 
the plastics used. Over time water ingress may become an issue. Fours years 
after the installation of a CN brand antenna, sourced locally so probably not 
counterfeit either, we had to replace it at OZ7IGY www.oz7igy.dk

RF wise 42 dB of gain IS an issue. Again at OZ7IGY, with 12 carriers in the air 
especially 13 cm and 23 cm, blocking and IMD were an issue before we mounted a 
BPF. I have taken apart the above mentioned antenna, a Motorola antenna and an 
eBay "hockey puck" antenna. The best design was clearly the Motorola one 
because it had a BPF after the pre-amp - probably because it was designed by RF 
competent people too. Each of the other ones had two FETs/MMICs in series and 
then a BPF. Of cause if no nearby carriers are in the air it may be less of an 
issue.

So designing a really good antenna and pre-amp may be a business opportunity. 
There are many hi IP3 MMICs available designed for GPS and the like purposes. 
SAW BPFs with <1 dB loss are available fairly cheap so one before the FET/MMIC 
with a 1 dB NF is the way to go. A DIY radome using standard materials from any 
hardware shop is attached.

Bo, OZ2M

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Simple open source microcontroller solution to tune DDS needed

[Bo Hansen]

Hi list

Here is an Arduino way to control AD9833, AD9850, AD9851, AD9912 and AD9913



Alternatively using an Atmega128A to control an AD9912:



Bo



___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

[time-nuts] 1pps isolation

[Bo Hansen]

Hi

TOSLINK devices may be one way to provide galvanic isolation through an optical 
connection. One possible solution can be seen here: 


Bo

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] TU30 jump second

[Bo Hansen]

Hi

OK I will try out to see what Lady Heather can do for me. However, I use a MCU 
for reading the GPS and not all the time so perhaps I have to change this.

Björn can you remember something about the reason for the behavior?

Thanks
Bo

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] TU30 jump second

[Bo Hansen]

Hi all

The data can be a bit hard to read in an email. So I will give it another try.

PC-time | Diff. | GPS-time | Diff.
...
011606.005 | 0.992 | 011604 |1
011607.013 | 1.008 | 011605 |1
011608.005 | 0.992 | 011607 |2 <--- The issue
011609.013 | 1.008 | 011608 |1
011610.004 | 0.991 | 011609 |1
...

I used a terminal program to log the NMEA data to a file and do the PC 
timestamp. Calculations were done in a spreadsheet by me. The PC-time is kept 
under control by Meinberg and also OK vs.  during the time 
of observation.

The PC-timestamp wobble is not the issue. It is a combination of the PC-time 
itself and the NMEA wobble. Nobody should expect the NMEA data to come at the 
same time every time relative to the 1 PPS. As Björn correctly points out it is 
always late and wobbles with processor load.

Sometimes the 2-something lag can last for many hours - I have seen more than 
48 h.

The issue is the "seconds jump". The issue is not the relative difference 
between the PC-time and the GPS-time but the jump, e.g. using Tac32 reveals 
that the TU30 is always ~1200 ms late on in case of the "jump second" ~2300 ms 
late.

I wonder if it has anything to do with the Week 1024 Syndrome?

Indeed the TU30 is a old device. I guess some 30 years if not more looking at 
the components. F/W I have no idea.

The 10 kHz seems unaffected.

Bo

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] TU30 jump second

[Bo Hansen]

Hi

The odd behavior is seen in NMEA mode. I have not tried in binary mode.

Bo


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

[time-nuts] TU30 jump second

[Bo Hansen]

Hi List

Like many of you I also use a Navman Jupiter TU30 in a GPSDO. Besides the 10 
kHz used for the PLL I also have a display showing time. But since a couple of 
years, Jan 15?, the time sometimes jumps -1 s and and then later returns by 
jumping +1 s Please see an example of the latter below:

PC-time Diff. GPS-time Diff
...
011606.005 0.992 011604 1
011607.013 1.008 011605 1
011608.005 0.992 011607 2 <--- The issue
011609.013 1.008 011608 1
011610.004 0.991 011609 1
...

I don't experience the same with a ublox GPS. I don't think I saw this more 
than two years ago and wonder if the GPS satellites send some correction data 
that the rather old TU30 misinterpret?

Any clues?

Thanks in advance
Bo

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.