For historical purposes here are the emails I sent Dave Brown and that he reply with regarding introduction dates:
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Hi Dave,
… the Sony/Tek portion of the spectrum analyzer page ( https://vintagetek.org/spectrum-analyzers/ ), put dates of introduction at the bottom of that page. There it says that the 3026 was introduced in 1998 while the 3066 was introduced in 1996. … Do you know where the source for the dates showing on that vintagetek webpage?
Reply
The information came from Koichi Sega who was a product planner, which I assume to be marketing, for the spectrum analyzers. I consider him to be the definitive resource on Sony/Tek spectrum analyzers. I know he reviewed my web page since he sent me corrections. He is still working for Tektronix and had firsthand knowledge of these products.
My assumption, and I will try to validate this, is the two companies worked together but also independently. Sony/Tek had products that Tektronix never sold and I suspect the opposite was true.
Tektronix distributed other vendor’s products in the US. Rohde and Schwarz was one such example. I seem to recall that Tektronix represented Advantest spectrum analyzers in the US so would not likely sell the Sony/Tek in the US. That 2000 date could have represented the end of the Advantest relationship and the introduction of the Sony/Tek products.
Dave