On Tue, Dec 31, 2019 at 08:06 PM, Gary Robert Bosworth wrote:
The 494A is supposed to be an upgrade to the 494. As far as I've investigated, the frequency, time and amplitude specifications are reasonably similar... however the digital, and software/firmware, improvements to the 494A standout more.
For an example of a difference, the (frequency span)/div for the 494A is 10 Hz to 10 GHz, whilst the 494 doesn't go below 50 Hz
For another example, of another difference, the frequency stability of the timebase appears to be an order of magnitude better for the 494A
Probably if you get the two operator guides... which are similarly laid out, you can parse out, other (minor?) differences in the hardware specifications tables.
For an example of a difference that affects the way a 494A can be used over a 494... the 494A has markers, and the 494 doesn't.
There are other things along these lines too... "features and benefits"... added to the 494A's software/firmware, such as the 494A's modes, that help the 494A make complicated measurements by partly automating them, and allowing them to be made by pushing a button. The 494 doesn't have much of that.
For example, using the 494A's "Pulse Mode", you can mark the peak of a main lobe, and the peaks of the side lobes, of a signal, by just pushing a button.
There are others on this list that will know far better than me about any significant differences between the two SAs. (I haven't mentioned anything about reparability, reliability, or usability... in comparison between the two.) But, you will probably have to tell use what you are trying to do, or measure, so they can zero in on significant differences.
Very generally, I'd venture to say, Tektronix made at least marginal improvements in the hardware, and significant improvements in the software/firmware, of the 494A over the 494. And if I was thinking of getting a 494A, over a 494, I might spend a hundred or two hundred dollars more to get the 494A, for features I reckon I might need; but in reality, would probably never use.
All the best and best wishes.