Antonio I0JX wrote:

Unfortunately the HP manual does not tell the frequency stability. No useful
information found searching the web.

Let me see if I can dig up the military version documentation, which I know
does.

Frequency measurement results:

- Just turned on. Frequency = 5.000 MHz Delta F = 0
- 15 minutes after. Delta F = -98 kHz
- 30 minutes after. Delta F = - 116 kHz
- 45 minutes after. Delta F = -132 kHz
- 60 minutes after. Delta F = -141 kHz
- 75 minutes after. Delta F = -147 kHz

That doesn't sound too bad. Sounds like you need to let it warm up for
an hour if you care about stability.

Again the question is: is my generator faulty or all instruments based on
the same (analog) frequency generation principle (charging a capacitor at
constant current) behave more or less the same?

You can get a signal generator with a precision oscillator which will be a
lot more stable. But function generators are not designed to be highly
stable or have very low distortion. They're designed to produce a wide
variety of waveforms. You lose a lot with the ability to get that variety.

The HP is just great as a sweep generator for touching up IF strips,
but I wouldn't put a key on the output and put it on the air directly.
The distortion is really too high for that.

I think a drift of 24 KHz/hr after an hour's warmup is not terrible.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."