[ARC5] Drift in BC-453 - more

[J Mcvey]

I have been musing about the "why" of VT oscillator instability. OK,  there's definitely a thermal element, but what parameters of the tube are most affected?I checked the spec on the resonating cap for the BFO and it is +/- 2 pf ! So the tube must be the culprit.Not being from the vacuum circuit design era, I took a look at some texts on the subject. It looks like the solution can become quite complex if one desires tight VT stability specs.

I'm going to put a cheezy Cmos LC oscillator together and let it run a while to see what kind of drift it produces. 
There were some 1 Mhz clock modules in the junk box, but there is no clean integer divide down that will arrive at 85Khz...dang!Maybe a 455 Khz resonator oscillator can be padded down to 425 Khz so it can be divided by 5? Or will that cause instability- on not work at all?Has anyone here tried heavy padding of a resonator? Did it work Ok?

  

    On Tuesday, December 12, 2017 8:56 PM, Kenneth G. Gordon <kgordon2006 at frontier.com> wrote:
 

 On 12 Dec 2017 at 0:00, spr at earthlink.net wrote:
> Yes, but it doesn't have the truly horrible AVC LO frequency pulling that 6A7and 6A8 have.
True, but both of those were early tubes that the 'K8 was supposed to supplant. > >> >6/12K8 is the absolutely noisest "converter" tube in Terman's entire long list. I hate the thing > >for that, but it does work well enough in the "ARC-5" receivers....> >> >Ken W7EKB > 
  

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