Looks like The US National Geodetic Service only calibrates antennas sold with 5/8-11 attachment points and defined orientations.
Maybe if Ardusimple glued some 5/8-11 PVC nuts per https://www.usplastic.com/catalog/item.aspx?itemid=28609 or some 5/8-11 angle grinder nuts per https://www.mscdirect.com/product/details/05896212 onto the bottoms of some its antennas and sold them as 5/8-11 survey mount antennas, they could also submit them to the NGS per https://www.ngs.noaa.gov/ANTCAL/index.xhtml
If the antenna really does provide comparable performance as the Tallysman per https://www.ardusimple.com/ardusimples-oem-antenna-vs-u-blox-tallysman/ , then having their antenna NGS calibrated could be a big selling point, and a good way to get your name out there.
The https://www.ardusimple.com/product/multiband-external-gnss-antenna-cover/ antenna has +10 euro option for the ublox antenna. Maybe you could add an option for survey-compatible mounting.
The NGS ANTCAL database has a Tallysman TWI7972+GP calibration entry https://www.ngs.noaa.gov/ANTCAL/LoadFile?file=TWI7972%2BGP_NONE.atx for a unit that doesn’t look too much more complicated than a flat unit bolted to a 5/8-11 adapter.
Isn’t the issue here that you can’t just slap a bolt on something? The calibration means you’ve got some significant rigour to your production and test processes so all the antenna you build are with tight tolerance of the one you got calibrated?
Perhaps someone has access to one of the GEO++ Robot Antenna calibration system, and can generate some usable data from that? http://www.geopp.de/robot-for-absolute-antenna-calibration/
You’d do better with something at least constructed for the job and adequately sized.
I believe Navilock sells this same one, but they charge 400 EUR
Take a look at the NGS detail for the Tallysman TWI7972+GP from the https://www.ngs.noaa.gov/ANTCAL/index.xhtml page (the navigation seems awkward on my Mac– choose Tallysman-Wireless and hover over the entries)- the submitted drawing doesn’t have the mount defined (https://www.ngs.noaa.gov/ANTCAL/LoadImage?name=TWI7972%2BGP%2BNONE.gif ), and from the pic the mount looks built up ( https://www.ngs.noaa.gov/ANTCAL/LoadImage?name=TWI7972%2BGP%2BNONE.l.jpg ). Maybe a http://www.tallysman.com/wp-content/uploads/23-0065-0-DataSheet.pdf with an unspecifed 100mm ground plane. If Ardusimple could use a jig to slap things on, I bet they could manage millimeter-level repeatability of the mount easily.
From the bottom-view pic as shown, I’m not sure that that’s made of standard as-sold Tallysman parts, or actually has the reuired 5/8-11 mount. If that’s a 100mm extra ground plane in the pic, then the inside diameters are about 16mm, 26mm, and 45mm, which do not quite match http://www.tallysman.com/wp-content/uploads/23-0065-0-DataSheet.pdf specs.
What I’m saying is they don’t have significant rigor and that Ardusimple could make their own version of a mount or buy a couple Tallysman 23-0065-0 adapters and similarly adapt them to attach them to their own antennas, and ship them to NGS for free calibration and good publicity.