[time-nuts] Leica AT-303

Bob Camp kb8tq at n1k.org
Thu Apr 23 07:47:32 EDT 2015


Hi

I guess it comes down to “how good is good enough?”

With any L1 only system, you are up against uncorrectable ionosphere numbers in the >=10 ns range. At 3 ns meter that is a  > 3 meter “variation”. 

The ionosphere does tend to correlate with that big light in the sky, so averaging over multiple days can address it in a position solution. Your TBolt will still
wander around, since it’s loop time constant is  << 24 hours. 

If you are trying to take 12 -2/+40 ns per day down to 10 -2/+40 ns per day, then sure a ~5 mm accurate position will be better than a ~1 M location. It’s doubtful
that there will be any measurable change in the TBolt’s output as a result. 

For $100, sure it’s not an expensive thing to try. I ummm ….. errrr .. seem to have a room full of antennas. My point is *not* let’s not do this. The point is that
everybody does not need to run right out and go antenna crazy (like me). The TBolt works quite well on a proper outdoor timing antenna that has a very good 
view of the sky.  Those antennas are nice and compact and sell for < $50. 

Bob

> On Apr 23, 2015, at 3:04 AM, Mark Sims <holrum at hotmail.com> wrote:
> 
> At least with a Tbolt,  they do help... and quite a bit.   When I was writing Lady Heather's precision survey code I tested it with several antennas (comparing the results to a cm level L1/L2 survey).  The Leica antenna and a couple of other survey grade/choke ring antennas were,  by far,  the best (results with a foot or so).   Cheap patch antennas were the worst (with maybe 5 foot errors).  
> 
> Some small L1 only survey grade antennas did pretty well... a couple of feet.  They are about 6 inches in diameter and and inch thick and very light.  I use one as my standard antenna.
> 
> -----------------------------------
> It’s not real clear that they have a significant advantage for L1 only operation with a Z3801. 		 	   		  
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