[ARC5] [Milsurplus] 500 Kc XMTR - now OT.

[Leslie Smith]

  Hello David,
  This is somewhat "off-topic" but at the other end of the EM spectrum a
  group in Hobart Tasmania have communicated by light between Hobart and
  Launceston - a distance of about 100+ miles.  Their success depended
  on overcoming many obstables (such a s finding a portable to solid
  mounting for optical gear) and resulted in some surprises.  For
  example, one would guess that a laser would be the best light source
  for optical communication.    The group found the precise, coherent
  nature of a laser was less useful than the dispersed (and weaker) beam
  from an incandescent source.   Surprising, yes?

I'm simply fascinated by experimental work that pushes some technology
to the limit.
A simple project such as a very stable conventional (L-C) VFO will
always catch my attention - even when more modern systems (such as
direct digital synthesis or a phase-locked loop) will provide better
performance by any measure (except, perhaps, simplicity).  

  73 de Les Smith
   vk2bcu at operamail.com

I "had a go" at building a stable L-C VFO.  I learned that people who
say some particular circuit is wonderfully stable have - by chance -
assembled parts with complementary temperature coefficients.  It's not
the circuit that matters - it's the style of construction and selection
of good-quality parts.

I know (for example) that when some-one claims  "This VFO is so stable
it will never drift - even near an open window - they don't have a
reliable method of measurement, or perhaps they live in a world of
fantasy.   No VFO, out of a box, is stable.  

At any rate, trying to replicate some well-worked over technology, such
as V.F.O. construction,  dispels myths and teaches one a good deal.   
We can see this in Bill Cromwell's comment about a regulated voltage for
the filament supply.  -  Les.



On Sun, Sep 17, 2017, at 07:07, David Stinson wrote:
> For those who get discouraged over the "5W ERP" rule,
> please take heart.
> In the 1980s on 180 KC- way lower and harder than
> 472 KC- we were able to make contacts over hundreds and
> thousands of miles- and eventually California to Hawaii-
> with antennas 30-50 feet (about 1% of a wavelength)
> and with MICROWATTS of radiated power.  Granted, the
> noise floor is much worse than it was 30 years ago, 
> but there are ways around that plus you've got a lot
> more RF to work with here.  It can be done.
> 
> 73 Dave AB5S
> 
> 
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