Fred's Notebook - CV's PLLs and more..

Good news Fred!  Here's hoping Theremin design isn't something of a mummy's curse.

And please don't think I'm trying to attack your design in any way, just wondering how much it has seen the lab - and evidently it has spent some time there!  BTW I ran across your division method of reducing noise today when looking for phase noise issues with the 4046.

Hi Dewster -

"Here's hoping Theremin design isn't something of a mummy's curse."

I did have some irrational moments when I wondered about a possible link between theremin "radiation" and cancer - Utterly and entirely irrational, I know that (levels of radiated signal, frequencies etc make these signals utterly harmless - a mobile phone is a nuke compared to a theremin being a firecracker) but fear often leads to irrational thinking, and thinking about those who died from cancer and were involved with theremins, well, one finds 'order' in noise if you listen to it long enough!

"And please don't think I'm trying to attack your design in any way" - Please, dont stop yourself from saying ANYTHING about my designs! - The only way we get anywhere is if we are forced to think, and by this improve!

I like the way you engage with the issues and state your ideas / questions - it is helpful! I also hope that I do not come over as critical regarding your designs, because I actually think you are probably going in the right direction in many ways.

The only kind of critisism I find objectionable is when someone says "that wont work" or "thats not the best way to do it" but then does not explain why they think this, or how to do it better.. Such people are just out to put one down or hold one back for their own (often hidden) reasons, and I think I have now learned to ignore such people - even if they have a reputation for being an "expert" in the field one is discussing.

 "BTW I ran across your division method of reducing noise today when looking for phase noise issues with the 4046" -

Really! was much said about it? - I would love a link if you have it, as I have only speculated based on what I (more by accident than design) discovered.

Fred.

"I did have some irrational moments when I wondered about a possible link between theremin "radiation" and cancer - Utterly and entirely irrational, I know that (levels of radiated signal, frequencies etc make these signals utterly harmless - a mobile phone is a nuke compared to a theremin being a firecracker)..."

Yes, photon (the EM quantum) energy is directly proportional to frequency.  I watched a PBS science program on mains (50/60 Hz) fields giving people who live near power lines cancer.  The scientist on the show said it was rather like your neighbor coming over during a hurricane, complaining that your cat was breathing on his tree.  The 60 Hz photon doesn't have enough energy to do anything to molecular bonds, and more of them won't change anything (the photoelectric effect).  The decades of expensive studies on this issue were more to calm the fears of the public IMO.

"...but fear often leads to irrational thinking, and thinking about those who died from cancer and were involved with theremins, well, one finds 'order' in noise if you listen to it long enough!"

The false "order" in the noise here (as it was in the PBS show) is the Texas sharpshooter fallacy where the target is drawn after the fact around naturally occurring disease clusters.  Whereas predicting the disease clusters before they occur would be real science.

"I also hope that I do not come over as critical regarding your designs..."

Fred, you are the very model of the rational mind, with a bonus doses of amenity and diplomacy.

"Really! was much said about it?"

Here's one link:

http://www.electronics-related.com/usenet/design/show/192995-1.php

Now that I read it again the root cause seems to be the speed at which the output transistors switch.  Kind of like metastability I suppose.

Another way that dividers reduce apparent noise is by the ratio of the noise to the cycle - increase the cycle but leave the absolute jitter the same and the UI jitter goes down.  I've seen this game played in datasheets.

That was an interesting link, I rarely bother to look at message boards when I search for technical data - perhaps this has been a mistake.

As to "false order", I was something of a weird kid - spent many hours listening for messages (got a bit into the idea of ET's making contact with wireless hams - read some crackpot book and was completely taken in..) on my old VT communication reciever..

I discovered that if I listened for too long, I would hear voices - and discovered that I would hear these even when it was impossible for me to be picking up a signal (a short on the co-ax antenna connector, LOL). At the time I did not understand why I heard these voices, and started to wonder about my sanity! (it's sort of funny thinking back, but at the time I was really frightened - particularly as I had spent my childhood being examined by shrinks because I was deemed abnormal )

Only years later I learned that this was a common expierience - that the brain will attempt to 'create' order from any chaos it encounters - and this principle applies to audio noise.

Fred.