Orientation for Trimble Micro-centered 33429.00-GP

You are correct Bill.

There's also a guide pin that prevents the antenna from being attached to the ground plane in the wrong orientation. Unfortunately, it doesn't prevent it from being installed upside-down, and a fair number of the photos on eBay show that a lot of people don't know this.

There's one on http://www.ebay.com/itm/282274269526&apos ;">eBay now that's installed in the ground plane upside-down:

I don't know how much this would affect the resulting position, but it's not something I'd care to mess with.

Seems like the difference in height of the plane relative to the innards could subtly alter the phase center and give you slightly different height measurements. In flipping it, the bottom view shows that it is rotated wrong - the connector would be SW instead of NE so the calibrations would be applied in the opposite direction and make twice the horizontal centering error.

The 4000sse and non-gp antenna I got from Woolpert via ebay seem to work fine except for minor scratchy problems with some of the front panel keys, that seems to be getting better with use, and a dead beeper so you you have to watch the display carefully when doing entries.

Mine came with the non-gp antenna discussed above, but I'm probably going to mostly use the older ST antenna which has a ground plane and seems to give just as good positions, and the larger diameter works better for measure-up past the tripod and tribrach.

There's another set from them selling Friday, in case someone wants to add to their fleet. There's also one without an antenna, with less provenance, and for more money.

So, I think we can put this to rest. EVERYTHING makes a difference. Everything.

And because the wavelengths are short (relatively) things that you think will not be a big deal, are.

By the way, that eBay antenna I linked to is listed as a Microcentered L2/L2, but it's actually a Compact L1/L2 -- if you zoom in on the bottom-side photo you can read the model number. Still a good antenna, and worth the $77.00 current bid if you need one, but not quite as good as the MC L1/L2.