[ARC5] Drift in BC-453 - more

[Kenneth G. Gordon]

On 13 Dec 2017 at 17:43, J Mcvey via ARC5 wrote:

> 
> Yes that was mentioned and may indeed contribute to a more constant cathode 
> temp.
> However the old time designers textbook devised ways to make the circuit stable 
> in a way that was independent of the tube characteristics.

Well...sort of. That depends on the level of stability one wishes to achieve. In point of fact, 
there are really NO circuits which CAN be completely independent of tube, or other active 
device, characteristics. One can reduce those effects to a certain minimum level, or 
compensate, at least partially, for them, but they are still there.

The "observer effect", (often mistaken for the Heisenberg Uncertainly Principle, which is in 
the domain of quantum mechanics) also can come into play here.

> Unfortunately, it ain't an easy fix!

Yes.

> Heater regulation wasn't mentioned , but it does make sense as a possible help.
> In fact , I have never seen an original design WITH regulated heaters. MAybe the 
> cost vs benefit wasn't there?

Yes, since the "benefit" at that time was stability which made any actual drift un-noticeable 
by the operator. Using more modern means of measuring ACTUAL drift shows that the 
stability achieved by those methods is "relative" to what actually affects operational ability.

We need to make sure we are all talking about the same thing.

I think Bill Cromwell's recent post of his experiences with stability is extremely important for 
our purposes.

Ken W7EKB

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus