The HP8664A is in the same family as the HP8643A, with many modules common.
On my HP8643A, the battery only seems to charge when the generator is switched on, not when in standby.
I, too, had calibration errors when I bought it.
There were two causes:
1. An internal connector that was not properly seated.
2. The battery issue.
These days, I switch it on for a few hours every couple of weeks- that ensures it holds last settings and does not get stuck in the cal. errors problems.
I¡¯m sure the battery could do with replacement- does anyone know where the battery is and what is a suitable replacement type?
Other than this issue, this is my chosen generator for reciprocal mixing measurements, as it has very low amplitude and phase noise for a synthesised generator of that era- I believe it was made for testing aircraft landing systems (ground segment- it weighs so much, an aircraft might struggle to take off, unless it was a B52).
