[TMC] VOX stability

[Duncan M. Brown]

Larry,

OK, I didn't realize that your problem was an open oven.

If you leave the VOX powered up for  a few days, does the outer oven ever
cycle?  

After the oven has been on for a few days, is it just a slow drift or does
the frequency jump around?  If it is jumping around, it is probably a bad
connection some where. (possibly caused by corrosion by the heat of the
oven.)

I have had contact problems with the Museum's SBE-9.  All the crystals are
in an oven along with the crystal selector switches.  Some of the switch
contacts are intermittent, or don't make contact at all.  I assume the bad
contacts are due to corrosion from the constant heat, but I can't get at
the switch contacts without tearing the whole oven assembly apart.

  --Duncan


> [Original Message]
> From: <TELEGRAPHER at att.net>
> To: <duncanancy at earthlink.net>
> Date: 15-Apr-09 22:06:35
> Subject: RE: [TMC] VOX stability
>
>
>  That's probably ture but without the ovens working the drift is way to
much for any of the digital modes as well as SSB.  I don't have a problem
with AM but that's the only place i use it.  As the ovens are not
functional due to corrosion having opened up some of the windings i'll have
to make do and tweak it as often as necessary i guess.
>
> If one is to take a look at the construction of the unit (ovens) and what
would be required to get inside to place heating resistors or elements of
some sort, one would or could have different aspirations.  Retaining the
calibration would be one major item of concern although with todays
frequency counters it would be less of a problem than it was 50 years ago. 
I suspect there may be some components that if replaced would enhance it's
stability but this old man isn't going to attempt the removal and
replacement of the oven assembly to do so
>
> If one could figure out how to repair the corroded windings on the
outside of the oven he could be in demand.  My outer oven light stays on
all the time and doesn't cycle at all.  The inner oven windings are
apparently the ones that are open.  I tried cleaning the loose ends and
soldering them together to retrun loop integrity to it.  Didn't work.  Must
be some sort of metal that i don't know about.
>
> Larry
> W0OGH
>
>
>   -------------- Original message from "Duncan M. Brown"
<duncanancy at earthlink.net>: --------------
>
>
> > The ovens in the VOX need to be on for at least 24-48 hours to
stabilize,
> > after that, stability is very good.  
> > 
> > The VOX-5 manual gives the temperature stability at 20 cycles per Mc
for a
> > 50 degree change in ambient temperature; and a 3 cycle per Mc change
for a
> > +/- 10% change in line voltage.  Unless the unit is installed outdoors,
you
> > won't see much frequency change from a change in ambient temperature.  
> > 
> > How much your transmitted frequency changes depends on how you are using
> > the VOX.  If you are using the multipliers in the VOX, then the
frequency
> > drift will also be multiplied.  If  are using a sideband exciter (SBE),
> > then any drift is the sum of the VOX (at 2-4 Mc) plus the drift of the
> > crystals in the SBE.
> > 
> > These units were designed to sit on one frequency and operate SSB/TTY
all
> > day without being constantly tweaked, so they should be plenty stable
for
> > amateur use, even in comparison to today's radios.
> > 
> > --Duncan, K2OEQ
> > 
> > 
> > > [Original Message]
> > > From: 
> > > To: 
> > > Date: 15-Apr-09 17:59:55
> > > Subject: [TMC] VOX stability
> > >
> > > What would the requirements as far as stability of a transmitted
signal
> > have been back in the 60's?  Whether high seas, Navy, Attache, etc. 
Now i
> > am asking this concerning an AM signal.  This unit with drift of + or -
100
> > cycles could not have been useful in CW, SSB nor RTTy service.  Should
an
> > end user expect 20 cycle accuracy?
> > >
> > > larry
> > > W0OGH
> > >
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