[Johnson] Ranger 1 Question/Problem

[Glen Zook]

Since the people who have been making frequency
stability measurements of the Ranger with the resistor
both inside and outside the compartment have found
that the VFO is definitely more stable inside the
compartment I would put a similar value resistor, but
in a higher wattage, inside the compartment.  This is
for temperature stability.

Glen, K9STH


--- Jim Brannigan <jbrannig at optonline.net> wrote:
> The conventional wisdom ( in all the on line
> literature) is to move the
> Ranger VFO VR dropping resistor to the OUTSIDE of
> the VFO box.
> I have done so, but the Ranger is still on the bench
> so a change is not a
> big deal...
> 
> What is the new "conventional wisdom"?
> 
> Jim
> 
> 
> > Makes sense to me, Glen. I don't relocate them
> anyway, I just change out
> the
> > original carbon unit with a 7.5 watt 18K Dale
> wirewound, and that seems to
> > work just fine. Doesn't change the wattage inside
> the VFO cage, just
> spreads
> > it out a little. Ha. Hope folks don't get the idea
> they don't have to do
> > anything about R3, though. It will fail for
> certain someday, and it's
> > failure mode will invariably be decreasing R, with
> a resultant increase in
> > load on VR tube, and concurrent increase in I as
> the poor overworked VR
> tube
> > works it's little guts out trying to keep up,
> which of course increases
> the
> > current through R3 again, which increases the
> heat, which increases rate
> of
> > R decrease, ad infinitum. A classic vicious
> circle, and the eventual
> result
> > is not pretty, as documented by some photos
> floating around the web.
> 
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> 

Glen, K9STH

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