[time-nuts] New (refurbished) LPRO-101 GPSDO

Sun Oct 17 16:09:26 UTC 2010

Also 

Regards,
David Partridge

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Bob Camp
Sent: 17 October 2010 16:09
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] New (refurbished) LPRO-101 GPSDO

Hi

The antenna should do fine just sitting on the roof. It will do better sitting over a ground plane. 

Does the antenna have a clear view of the sky to the south?

Bob

On Oct 17, 2010, at 10:15 AM, David McClain wrote:

> Well, not exactly an urban jungle here, but there could be multipath off the neighbor's home... Thanks for that suggestion. I will try moving the antenna about.
> 
> When I first deployed it, the GPS would go solid reception for a while, and it actually claimed to lock, after only an hour or so. But it kept losing the birds and would go back into hunt mode after about 20 minutes of lock time. I wasn't sure that I could trust the lock indication after so short a time. And I didn't like the sporadic lock conditions.
> 
> So I tried duct taping the antenna to the roof tiles that I could reach and got solid GPS reception, but no lock.
> 
> The antenna is a little black hockey puck with a magnetic base. I wonder if it would do better affixed to a metal ground plane?
> 
> First time user of a GPSDO and so I don't know what to expect. But I'm also beginning to understand better that a GSPDO probably is more than was warranted for the needs of a solid reference oscillator for radios. Now that I'm learning more about Rb and GPSDO's in general, I probably could have got by quite well with just a bare LPRO. And I am also beginning to understand that GPSDO's don't necessarily have internal Rb references -- looks like the T'Bird is just a really good OCXO with a GPS discipline. And everyone is raving about T'Birds... The LPRO has an internal Rb reference and an untamed VCXO.
> 
> Thanks for all the advice!
> 
> Dr. David McClain
> Chief Technical Officer
> Refined Audiometrics Laboratory
> 4391 N. Camino Ferreo
> Tucson, AZ  85750
> 
> email: dbm at refined-audiometrics.com
> phone: 1.520.390.3995
> web: http://refined-audiometrics.com
> 
> 
> 
> On Oct 17, 2010, at 06:07, mike cook wrote:
> 
>> 
>> 
>> Le 17/10/2010 11:55, David McClain a écrit :
>>> 
>>> I just received my LPRO-101 with a GPSDO control on it, from TenMhz.com. After fiddling with getting a good placement for the GPS antenna, so that it doesn't keep losing the satellites, I have been attempting to discipline the oscillator for more than 24 hours.
>>> 
>>> At this point, the LED has been toggling red / green for the past 24 hours which indicates solid GPS acquisition and < 5e-8. But it isn't locked to NIST until it turns solid green which indicates < 5e-11.
>>> 
>>> Since this is a first deployment at my location, is it reasonable behavior for it to take longer than 24 hours to lock to NIST through GPS? Or do you think something may be wrong with the device.
>>> 
>> I don't have this box or an LPRO, but if the manafacturer says 24hrs is OK, then I guess that should be enough.  You may need to give them a call. However am wondering if you are getting reflected path GPS signals. You said  that you had to fiddle with the antenna placement. Are you in an urban jungle? I have a situation where I can see satellites at all times, but once or twice a day I am getting strong reflected signal which is disturbing the GPS 1PPS. It is due to buidings opposite my north facing office where the antenna sits. The issue is seen with my TBOLT, Z3801A and  independent Oncore GPS engines all of which are not the latest hardware.  That would cause the PLL to be constantly chasing a moving target.
>>> I already know by comparison to WWV that I'm within a few mHz of 
>>> being aligned, but noise in the measurements, human impatience, and 
>>> wander in the soundcard clock, prevents me knowing any better than 
>>> this. So already I'm < 5e-10. But that's about all I know until I 
>>> see it lock. (If it ever does...)
>>> 
>>> eh?
>>> 
>>> Dr. David McClain
>>> Chief Technical Officer
>>> Refined Audiometrics Laboratory
>>> 4391 N. Camino Ferreo
>>> Tucson, AZ  85750
>>> 
>>> email: dbm at refined-audiometrics.com
>>> phone: 1.520.390.3995
>>> web: http://refined-audiometrics.com
>>> 
>>> 
>>> 
>>> On Oct 15, 2010, at 16:00, Magnus Danielson wrote:
>>> 
>>>> On 10/16/2010 12:08 AM, Bob Camp wrote:
>>>>> Hi
>>>>> 
>>>>> It's a crazy world when it comes to self signed certs.
>>>>> 
>>>>> You have at least 5 OS's you need to consider (MS, Linux/FBSD, OS-X, I-OS, Android). You need to think about both browsers and mail clients. Each of those come from a half dozen sources on each platform. Then you have configuration options on each. That's a lot of combinations.
>>>>> 
>>>>> Each combo seems to have a different idea of what not to do when they see a self signed cert. If you want to be able to handle all of them, even "real" certs may have issues. There are indeed several common combo's that are a major pain with a self signed cert.
>>>>> 
>>>>> No, I didn't write any of the code with the problems in it. I also don't want to get into the details of what and where. This really isn't the forum for that sort of thing. I'm not out to bash any particular solution, only to point out that there are indeed issues.
>>>> 
>>>> Do handle part of the mess, we have setup our local root cert at the computer club, and then sign our server certs to that. I did a major overhaul on the infrastructure for that. It is still not "real" safety routines, but ah well. We provide a cert download which quickly solves the cert issue with most browser.
>>>> 
>>>> Seems to work for our myriad of server and client OSes and clients.
>>>> 
>>>> There is various ways to get "real" root certs, but depending on degree of uhm... safety... it may be argued of their capabilities. There is efforts to build a chain of trust for a stable free root cert, but it is so far nog included in any major browsers.
>>>> 
>>>> Essentially it's a mess. I'm only scratched the surface here.
>>>> 
>>>> Cheers,
>>>> Magnus
>>>> 
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>> 
>> 
>> 
>> 
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