There are two types of Oscilloquartz GPSDOs appearing on Ebay: For now, I would avoid the OSA-4530. I have been unable to talk to it. The version being sold now may have non-standard firmware. All commands return an "unknown command" error. The Oscilloquartz GPSDOs that use the Star-4 module work well with Lady Heather. The first versions that were released needed some modification to connect the "management interface" to the RS-232 port, but the later versions have the mod. ------------ > Or would it be better to buy the OscilloquartzOSA-4530 GPSDO and use LH?