Re: [time-nuts] Improving performance of a GPS antenna...?

2012-04-05 Thread Morris Odell
Thanks for the replies. Yes it's definitely 5V from the receiver. That advice re the pipe mount sounds good - that will be the next step! Morris -- Are you sure that the Oncore VP sends the right voltage to the antenna? This type need

Re: [time-nuts] NTP jitter with Linux

2012-04-05 Thread Chris Albertson
On Thu, Apr 5, 2012 at 1:03 PM, wrote: > An older laptop (Pentium M for instance) can be had for $80 or so any day of > the week, won't take much space, is completely standalone (built-in keyboard > and display, built-in battery backup) and sips power when idle, which it will > be most of the

Re: [time-nuts] Improving performance of a GPS antenna...?

2012-04-05 Thread Chris Albertson
On Thu, Apr 5, 2012 at 2:28 PM, EB4APL wrote: > Hi, > > Are you sure that the Oncore VP sends the right voltage to the antenna? >  This type needs 5 V and most pucks are designed for 3.3 V .  According to > the manual the VP sends 5 V to the antenna but anyway it is easy to measure. > > Regards, >

Re: [time-nuts] Improving performance of a GPS antenna...?

2012-04-05 Thread EB4APL
Hi, Are you sure that the Oncore VP sends the right voltage to the antenna? This type needs 5 V and most pucks are designed for 3.3 V . According to the manual the VP sends 5 V to the antenna but anyway it is easy to measure. Regards, Ignacio, EB4APL On 05/04/2012 3:43, Morris Odell wro

Re: [time-nuts] NTP jitter with Linux

2012-04-05 Thread Dennis Ferguson
On 5 Apr, 2012, at 13:03 , shali...@gmail.com wrote: > An older laptop (Pentium M for instance) can be had for $80 or so any day of > the week, won't take much space, is completely standalone (built-in keyboard > and display, built-in battery backup) and sips power when idle, which it will > b

Re: [time-nuts] NTP jitter with Linux

2012-04-05 Thread gary
Old doesn't necessarily mean it sips power. Power consumption is based on "buckets of charge" shuffled through the chips. Older processes have more capacitance, hence bigger buckets for the same amount of work. Further, notebooks have all the power saving features that are causing (potentially

Re: [time-nuts] NTP jitter with Linux

2012-04-05 Thread shalimr9
An older laptop (Pentium M for instance) can be had for $80 or so any day of the week, won't take much space, is completely standalone (built-in keyboard and display, built-in battery backup) and sips power when idle, which it will be most of the time. The only issue is that you might be tempte

Re: [time-nuts] NTP jitter with Linux

2012-04-05 Thread Chris Albertson
On Thu, Apr 5, 2012 at 11:11 AM, Hal Murray wrote: > > My guess on the original question is that keeping the CPU busy puts junk into > the cache so the whole interrupt processing path takes every possible cache > miss. Cache misses are nanosecond level events not tens of microseconds. If you see

Re: [time-nuts] NTP jitter with Linux

2012-04-05 Thread Hal Murray
My guess on the original question is that keeping the CPU busy puts junk into the cache so the whole interrupt processing path takes every possible cache miss. NTP doesn't care how fast that code is as long as it's consistent. (Of course, you probably get a different answer, but we are discus

Re: [time-nuts] would an optical primary standard provide any general benefit?

2012-04-05 Thread Magnus Danielson
On 04/03/2012 01:10 PM, Jim Lux wrote: On 4/3/12 12:49 AM, Azelio Boriani wrote: Yes, but nonetheless why not develop more stable primary clock sources? We can always take care of the dissemination in the meantime and try to develop a more precise time transfer method. On Tue, Apr 3, 2012 at 2:

Re: [time-nuts] Book by William Riley

2012-04-05 Thread Magnus Danielson
On 03/26/2012 10:34 AM, Rex wrote: On 3/24/2012 3:54 PM, Magnus Danielson wrote: and the Hanbook of Frequency Stability Analysis You didn't mention looking at that one. Any comments about it? Considering that it is available from NIST as SP 1067 and that it is also downloadable as PDF from

Re: [time-nuts] TAPR "TADD-2 Mini" PPS Divider Now Available

2012-04-05 Thread Magnus Danielson
On 03/26/2012 01:38 AM, John Ackermann N8UR wrote: [ Apologies if this is a duplicate. ] We are happy* to announce that TAPR is now accepting orders for the TADD-2 Mini (or T2-Mini) pulse-per-second ("PPS") frequency divider: http://www.tapr.org/kits_t2-mini.html. Congratulations! Good work!

Re: [time-nuts] Improving performance of a GPS antenna...?

2012-04-05 Thread michael cook
There was some discussion on this here a while back. I had issues with bad reflections and wanted to know if there was a possibility of creating a variable mask angle. I had found a reference to a program developed by Leica to do just that. The links however ended in a dead end. It would be a n

[time-nuts] OT: 'Navipedia': the reference for satellite navigation know-how

2012-04-05 Thread David J Taylor
'Navipedia': the reference for satellite navigation know-how. "Satellite navigation is progressing swiftly, in fact so swiftly that its printed textbooks can't keep pace - so ESA has introduced its own wiki-based information source, Navipedia, which is also the first ever ESA technical wiki op

Re: [time-nuts] Improving performance of a GPS antenna...?

2012-04-05 Thread Azelio Boriani
How do you know it is coming from a specific direction? There is a terrestrial L-band transmitter? A radio link? Try to put a screen n*lambda+lambda/2 from the GPS antenna to create a null for the offending L-band frequency... On Thu, Apr 5, 2012 at 2:49 PM, Chuck Forsberg WA7KGX N2469R wrote: >

Re: [time-nuts] Improving performance of a GPS antenna...?

2012-04-05 Thread Chuck Forsberg WA7KGX N2469R
What sort of interference?? What is causing it? Any possibility of correcting it? I am interested in more information. Will look for whats later in the thread. I have a situation where there is interference coming from a specific direction (close to the horizon). Is it feasible to block/att

Re: [time-nuts] NTP jitter with Linux

2012-04-05 Thread Javier Herrero
El 05/04/2012 12:20, Azelio Boriani escribió: On a side note, speaking of deterministic systems, why has no one built a GPSDO with an FPGA yet? Or an NTP server? :) Oh, I've done that (an NTP server, not GPSO) in a Cyclone III FPGA. But well... it has a Nios-II CPU and runs Linux, so I suppose

Re: [time-nuts] NTP jitter with Linux

2012-04-05 Thread Mike S
On 4/5/2012 2:51 AM, David J Taylor wrote: Mike, have you tried FreeBSD instead? Does it show the same problems? I have a couple of Soekris Net 4501s running FreeBSD and NTP. They don't have much jitter, but they're a very different architecture. The machine with the jitter is my home "do al

Re: [time-nuts] NTP jitter with Linux

2012-04-05 Thread Azelio Boriani
>>On a side note, speaking of deterministic systems, why has no one built a GPSDO with an FPGA yet? Or an NTP server? :) Yes, I have: I have a GPSDO entirely on a 50Kgates FPGA (Spartan3 XC3S50) without microprocessor. GPS is the iLotus M12M and OCXO is a Morion MV201, the DAC is... well, not exac

Re: [time-nuts] Improving performance of a GPS antenna...?

2012-04-05 Thread bg
Jim, > There's a new "choke ring" style antenna (patented, of course, and they > deserve it) which uses spikes instead of solid rings. And, they wrap the > choke over a hemispherical surface as opposed to on a plane. > > Much tougher to design and fabricate (no buying sets of cake pans any > more