Thank you Robert and everyone else replying. I am collecting all the suggestions and working out which route to take, or whether its simpler to just keep on entering the offset or just remember the error as I have been doing.

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But most of all I am filled with simple disbelief that this instrument was left so incomplete in self-cal capability, unless it is just well hidden, in which case why is it so well hidden?

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The point about it being close so it’s very wide spec is the soft option, as the error is VERY constant, across frequency, time and temperature. I think it could hold +/- 0.5 dB if done properly. The instrument reminds me of the schoolchild that ‘could do better, if only he would only try’. A few decades ago I used a different Spec An that was wonderfully calibrated. Then it went off for cal and on return the horizontal span cal was miles out; signals near the edge of the screen were almost 10% off. I complained and the answer came back from the 3^rd party test lab ‘its within spec’. But someone had fiddled as it was not like that previously. However, that is another story.

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Keep it coming, as its also crystal clear that I am far from not alone with this problem.

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Kind regards to everyone.

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Colin

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