Sig Gen out?

[boater sam]

My ancient Grundig AS4B signal generator appears to have gone out of calibration and I have not got another to check it against.

Is there a way to check the calibration using a radio or anything else simple?

Sam.

[Mike Watterson]

Tune radio to a station of known frequency.
Adjust generator with a loop on o/p to correct dial markings for that.
Adjust generator electronics for zero heterodyne beat.

[boater sam]

Thanks Mike, that is what I was considering. Of course I realise now that the radio does not need to be accurately RF aligned as long as I know the transmitted frequency.

[Mike Watterson]

Thanks Mike, that is what I was considering. Of course I realise now that the radio does not need to be accurately RF aligned as long as I know the transmitted frequency.

Exactly!

If you have a very good TRF (or tuned ferrite & strong signal) and suitable scope you can put tuner to Y in and sig gen to X in once they are close and make an ellipse. Zero rotation means you have matched!

A regular crystal osc isn't as accurate unless it's calibrated ovened or TCXO.

[boater sam]

Now Mike, ovened I know but TCXO you will have to translate for me.
I will try firing up a 'scope but my Telequiment has a habit of smoking every time though It seems to carry on working!
Sam.

[ppppenguin]

TCXO: https://uk.rs-online.com/web/c/passive-c...cillators/

Capable of 1ppm accuracy over a temperature range without too much trouble. The best modern ones with digital compensation can get towards 0.1ppm, thus overlapping with the low end of ovens but cheaper and smaller. This was very relevant to me when designing TV sync pulse generators where 0.2ppm was needed to fully comply with the PAL standard. A bit too tight for earlier TCXOs and very loose for ovens.

[PerdioPal]

And a TXCO doesn't need warming up, lower power too. And my old Quarzlock 198kHz reference doesn't work anymore.

[PerdioPal]

For frequencies lower than MW (where most strong "reference" signals exist) set the sig. gen. to square wave and use harmonics.

[Mike Watterson]

Really old ones don't have square waves, but often have enough 2nd or 3rd harmonic. The harmonics on my 1944 model work to align a VHF Band II radio (and usually FM not needed).