[time-nuts] Maser 0.7 nsec jumps solved
paulswedb at gmail.com
Fri Jun 3 09:24:39 EDT 2016
My head is precisely in the get it away from the unit approach.
Did not mention it for the following reason.
Its well understood and for time-nut boring. Its more fun to figure out
peak currents and such.
But I tend to fall into the get it done camp and move on.
That doesn't mean its a simple answer. Flex duct is bad. So only use it in
the last few feet. You want low resistance hard duct.
Then the fun of the return feed. Often overlooked and poorly considered.
On Fri, Jun 3, 2016 at 1:00 AM, Jim Palfreyman <jim77742 at gmail.com> wrote:
> Hi All,
> Thanks so much for your input and thoughts. It has really proved helpful
> here at the observatory.
> As it turned out we easily obtained a zero-crossing solid state relay so we
> thought we'd try it.
> And, drumroll......
> It made things so much terribly *worse* than ever before. (As predicted by
> many of you above.)
> We are going to try a SSR that switches at the peak - but we need to order
> one. So stay tuned on those results.
> There is of course the "move the bloody thing far away from the maser"
> solution which could end up being a serious option. These air conditioning
> units are small and cheap (window-type), so we are trying to find the
> cheapest solution - and if that ends up being some ducting - so be it!
> Jim Palfreyman
> On 26 May 2016 at 13:13, Andy <AI.egrps+tn at gmail.com> wrote:
> > On Wed, May 25, 2016 at 12:59 PM, Mike Monett <
> timenuts at binsamp.e4ward.com
> > >
> > wrote:
> > LTspice shows switching at 0V is the best point in time. ...
> > Bzzzt! Your simulation is seriously flawed, and your conclusions are
> > wrong. What you forgot, or may not have realized, is that SPICE's
> > transient solution is obtained by having the signal sources already
> > on (at the moment of the Big Bang) and set to their initial value, so the
> > current through L2 is limited by DC conditions. That is not anything
> > to switching the driving voltages on. It is having one waveform sit at
> > +169.7V DC for a very long time ('forever'), and then letting it follow a
> > cosine wave.
> > Re-run the simulation with "UIC" added to the .tran statement (.tran 50ms
> > uic) and see what it shows. Using UIC forces the initial voltage to be
> > at time=0, the start of the simulation. That's like having the switch
> > initially open.
> > Or if you don't like that, multiply the sources by a PWL waveform that
> > starts both voltages at 0V and then switches them on, a few milliseconds
> > into the simulation, with the appropriate phase.
> > Or use an actual switch. LTspice has a switch element you could use.
> > I guarantee you, the case with the voltage switching on at the 0V point
> > the voltage waveform, causes greater currents.
> > The smaller surge current happens when the source is connected at the
> > moment when the current i(t) would be 0A if it were a continuous
> > For an inductive load, this happens when the voltage v(t) would be +/-
> > (or near peak, for a real load which has both inductance and a little
> > resistance). This condition also results in no surge, thus no L/R decay.
> > All of this might not be relevant to a mechanical system, where surge
> > current is caused by rotational inertia, rather than anything electrical.
> > Regards,
> > Andy
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