EIP 5xx Frequency counters?

[Stray Electron]

  Can anyone explain the difference between the 5xxA and the 5xxB counters?  Also does anyone have a list of the circuit cards used in the various models?  Finally, on some models, EIP offered an option 12, "Improved Sensitivity Guaranteed".  Does anyone know what was involved with that? My manual mentions it under the options but it's not mentioned anywhere else that I can find.   Even the sensitivity specifications fail to mention it.

[HighPrecision]

  Can anyone explain the difference between the 5xxA and the 5xxB counters?

x=5  for 18/20 GHz models
x=8  for 26.5 GHz models

53x/53xB: lowest price units, missing some functions of higher models (i.e. freq. limits)
54x/54xA/54xB: standard units
57x/57xB: as 54x with source locking circuits added
58x/58xB/58xC/59xx: Pulse counters (different HW)
25B/28B: as 54xB models in small case and band 3 power meter standard

'A' models exists only for 545/548

5xx(A) <> 5xxB major differences are upgraded CPU (double clock), new firmware structure, new EEPROM for cal data, GPIB interface standard (no opt.08) and others.

  Also does anyone have a list of the circuit cards used in the various models?

53x/54x and 57x use similar cards, differences are related to CCN numbers of production history, small or big modifications on components. 'B' models have a totally different CPU card and major mods on some other.

in the 'B' transition from older models there is a big confusion, new CPU card is installed in some old models, in example: 545A CCN 2209, it's also confirmed by the CCN 2209 manual.

Yes, exist a list of cards P/N related to CCN numbers.

  Finally, on some models, EIP offered an option 12, "Improved Sensitivity Guaranteed".  Does anyone know what was involved with that? My manual mentions it under the options but it's not mentioned anywhere else that I can find.   Even the sensitivity specifications fail to mention it.

I know that the lowest price 53x/53xB counters have a standard minimum guaranteed sensitivity on band 3 lower than others models, 5dB less, and the Opt.12 upgrade this at the same level of 54xx/57xx models.

[Stray Electron]

  Thanks. That's exactly the kind of information that I was looking for.