[Radio Wrangler]

With a synthesiser, you have to be quite careful in talking about frequency.

If something is exactly 100kHz out, then it sound like the loops are locked and the control data is wrong.

If loops are unlocked, then there could be any amount of error. It is most unlikely that it will be an exact round number and it will drift about a bit.

So looking for exactness or digit is a quite helpful indication of the sorts of things it could or could not be.

I've designed multiloop synthesisers (and DDS assisted ones, and Fractional-N ones) but I was a bit spoiled by having fast scopes and spectrum analysers to hand. It's harder to see what's happening without such things, but looking at the tuning voltage on each loop is a very good approach.

I wrote some description of how multiloop synths work for the ARRL handbook. It's in any edition from 1995 onwards in the oscillators and synthesisers chapter.

David