[time-nuts] Thunderbolt antenna?

[WarrenS]

Good information to know, if one is doing survey work.
But some NON-Nut needs to ask, SO WHAT?
A 3 foot error may cause + - 3ns of additional phase time error, which is 
well below the short term GPS noise level.
If that is averaged over the 500 or so second TC loop or the 48 hrs supper 
survey time, it's more like an additional 1e-12 to 1e-15 or so freq noise 
error per day, which is not a problem for the normal NUT.

I've compared that antenna to an cheap INDOOR puck antenna on a properly set 
up Tbolt and the effects are hardly visible on a supper modified, 
temperature controlled, double oven, externally controlled Tbolt at the 
1e-12 range, So for the extreme nut a great antenna is a Must, but for the 
more Normal nut, they are not going to see any difference.

And then there is the non explained point that what causes the most antenna 
reported time error of the typical overhead satellite is not position error 
but elevation errors, and the reported height seem to vary by 10 + times 
what the Lat/Lon does and yet does not have nearly as much effect on the 
GPSDO.

And back to the original question,
What I have found is that my $20.00 GPS antenna which looks to be the same 
as eBay Item number: 390147799311
WITH A PROPER PIE PAN mounted UNDER IT, works Almost as good as the $1000 
unit (within a 1 ns) on my Tbolt.

Or if you want to save even more money and can stand an addition couple ns 
of phase noise,  just put your cheap puck antenna on a pie pan and place 
that on the roof with a clear view down to 30 deg.
Using the latest Lady Heather signal level plot to see what your antenna's 
clear view is can help a lot


ws

*************
Mark Said:

All the choke ring antennas were similar in performance.   The Aero/Leica 
one is optimized for the L1 freq only.

All the other choke rings that I tested did L1/L2 which compromises 
performance a bit which did show up in the data (but at a level that could 
just have been random luck of the draw).  Where the L1 only antenna was 
getting precision survey offsets in the one inch area,  the L1/L2 units were 
in the 2-3 inch area.

Lesser survey grade antennas might be in the 6-12 inch range.   Conical 
timing antennas in the 1-2 foot range (they are just a higher quality patch 
antenna under a conical radome).   Cheap automotive patch antennas in the 3+ 
foot range.

**********************
Hello,

I'm looking for a decent outdoor antenna for my Thunderbolt...  I need to
graduate beyond the puck-antenna in the window sill.

Any recommendations and/or sources (the lower cost, the better of course!)?


Thanks,

Dave