Hi Bob,
Well,... sort of... I live in a rather cramped housing development,
where the neighbors wall is about 20 feet from my window, and his
wall is about 12 feet high. So that seems rather marginal for a
southern view from the windowpane of my lab.
As it happens, I moved the antenna about 4 feet lower, to a slightly
more restricted view of the sky, and the LPRO pretty quickly locked
to its best state. Then after fiddling some more with the antenna it
must have lost the birds, but still remained in its second-best
state. Now after more fiddling, the sats were reacquired and the LPRO
is back to its best locked state. What a huge difference this makes.
Incidentally, the antenna was originally located about 1 foot from a
Comcast coax line running around the house, just below the eaves. I
have had no end of frustration with Comcast equipment, and so I
wonder if that was the culprit. Right now the antenna is sitting
slightly higher for a better view of the south, but careful to keep
at least 3-4 feet from the Comcast coax line. Everything is working
great at the moment.
Very happy camper. Thanks so much for all your input. I'll give the
groundplane idea a try with one of my wife's cookie sheets...
Cheers,
Dr. David McClain
Chief Technical Officer
Refined Audiometrics Laboratory
4391 N. Camino Ferreo
Tucson, AZ 85750
email: [email protected]
phone: 1.520.390.3995
web: http://refined-audiometrics.com
On Oct 17, 2010, at 08:09, Bob Camp wrote:
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: [email protected]
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: [email protected]
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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