[ARC5] Drift in BC-453 - more

[John Hutchins]

Watching the conversation take shape over time:

If the tube is the culprit in MO drift,  I may have miss remembered,  I 
read some where that regulating the filament voltage to the M.O. 6J7 ... 
, and the Detector (12,6)K8 may help in subduing the tube drift, do to 
changes in temperature do to voltage swing.   True or not true?

Thanks
Hutch

On 12/13/2017 9:54 AM, J Mcvey via ARC5 wrote:
> 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
> >
>
>
> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=icon> 
> 	Virus-free. www.avast.com 
> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=link> 
>
>
> <https://mail.yahoo.com/?soc_src=mail&soc_trk=ma#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net <mailto:ARC5 at mailman.qth.net>
>
> This list hosted by: http://www.qsl.net <http://www.qsl.net/>
> Please help support this email list: http://www.qsl.net/donate.html
>
>
>
>
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/arc5/attachments/20171213/2b621369/attachment-0001.html>