[time-nuts] How good is the left end of your ADEV curve?

Jim Palfreyman jim77742 at gmail.com
Wed Jan 25 22:57:12 EST 2017

I can't recall what I said before, but it *has* been done in the backyard
before. There's good news and bad news. The good news is that all the
software for processing your data: coherent dedispersion, folding, moving
all arrival times to the solar system barycentre, Einstein delay, Shapiro
delay, fitting, analysis etc is open source. You need DSPSR, PSRCHIVE, and
TEMPO2 and a unix machine to run them on.

The bad news:

Vela had a declination of -45 10 35 which means it's not visible very often
for you northerners. The second brightest pulsar has a similar declination.
After that, forget it - they are too faint.

Observing of individual pulses requires around a 20+ m radio telescope with
a receiver cooled to 20K (at ~1400 MHz). However using the above software
you can fold your data on the latest pulse period (which I can provide if
needed) and this then brings things down to a possible level:

You'll need a dish that can track. One that is 2 m across might just work.
Frequency choice is important. The lower the frequency the stronger the
pulse, but also multipath scattering smears the pulse out. Around 1400 MHz
is a good choice for removing the scattering, but may be too faint for
small dishes. If you went with ~600 MHz that could work - but do check any
local RFI.

If you didn't track, but just waited for the pulsar to pass through the
beam, you'd get about 2 minutes of data. That *might* be enough to fold and
get a signal.

It'd be a long, but awesome, project to work on.

The really cool part is that Vela glitches (speeds up) in rotation ~3 years
by around deltaf/f =10^-6 and you could measure that. It just glitched in
December (and I was observing at the time!), so you have another 3 years to
get building.

As to timing, any half decent GPSDO would be fine.

Oh, almost forgot, you'd also need a sampler.

Jim Palfreyman

On 26 January 2017 at 13:58, Tom Van Baak <tvb at leapsecond.com> wrote:

> > What can I do at home, to observe such processes? Or is it way beyond
> > any imagination to participate in any such experiments?
> >
> > Volker
> LIGO is a billion dollar experiment, involving thousands of PhD's so it
> will be some time until you can do that sort of stuff alone at home, or
> with your family.
> Jim Palfreyman has mentioned before what it would take to do Pulsar
> measurements as a home experiment. Search for the old threads or he can
> jump in to remind us why it can't or hasn't been done yet. See also the
> thread a month ago about a DIY H-masers since you'll want some of them on
> hand before you start.
> It's worth spending time reading anything about LIGO. The experiment is
> out-of-this-world clever, complex, sensitive. And it actually works! Unlike
> the particle physics tree, which seems to be nearing the end of bearing
> fruit, LIGO is at the very beginning of an entirely new way to study the
> universe.
> /tvb
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