[time-nuts] Re: HP 8663A: option 003

[John Miles]

> HP 8663A option 003 gives guaranteed/specified SSB performance for the
> 640 MHz output. What exactly does this mean? Are there hardware
> differences in the reference section of the 003 units in comparison with
> non-003 units? Or, was the hardware the same and HP simply categorized
> them according to measured SSB performance? If it's the latter, what
> implications does this have for buying 003 or non-003 units now? I think
> I remember reading somewhere on this list that 10811A SSB
> categorizations don't matter much after this amount of aging. Maybe the
> same thing applies here?

Option 003 was aimed at customers who needed to use the synthesizer with a 3048A system equipped with an 11729B/C downconverter.  AFAIK all of them had 640 MHz available on an SMC jack under the top cover, but it seems that only the -003 units brought it out to the rear panel.

Many of the 8662As were built without the rear-panel jack, but it can be added easily enough.  I've never seen an 8663A that didn't have it.

Whether a given unit met the PN requirements for option 003 depended on not only the 10811 OCXO but on the rest of the reference multiplier chain as well, including the 40 and 160 MHz crystal filters.  It's unlikely that all of them met the spec, given how tight the 100 Hz limit is in particular.  So there would have been some selection involved at the factory.  It might have come down to something as banal as fan blade balance.

With regard to the SAW oscillator, none of the 8662/8663 generators included one.  But if you didn't have option 003 -- or if you didn't have an 8662/8663 at all -- the SAW filter stage at the 640 MHz input on the 11729B/C could be configured as a standalone oscillator.  The filter was necessary in any case because the 640 MHz output from the generator was full of spurs from the other stages of the reference multiplier chain.

-- john