[Vintage_RC]

Recently I needed a decent signal generator for a project I was working on. I got my Dymar 1525 out of the back of the equipment cupboard, this is a 1970's bit of equipment with a useful range of features but despite being all transistor is quite bulky and heavy (see photo). Since I hadn't used for some considerable time I decided to run some tests on it to make sure it was performing acceptably. One thing I noticed (and something I remember from last time I used it) was the long period before the slow frequency drift stabilised. I can live with that, I just leave it on all the time while it might be required. Everything looked OK and I decided to check the AM modulation, as you can see the envelope at 50% mod looks to be as you would expect. Out of interest I took a look at the spectrum with and without AM modulation (see photos). I was surprised to see quite noticable asymmetry with AM modulation (in FM mode it is symmetrical), I assume this is due to some unwanted FM component. I don't think this will cause any problems for my application but I wondered if this is typical of a generator such as my Dymar.