[time-nuts] nubie querie

Paul Boven p.boven at xs4all.nl
Fri Mar 5 22:33:00 UTC 2010


Hi Tom, everyone,

Tom Van Baak wrote:
> See: http://www.leapsecond.com/museum/pulsar for some
> pulsar ADEV stability plots and links to many research papers
> with all the details.

Your page starts with the question "if it was possible for an amateur to 
receive pulsar signals?". Turns out you can, at least the particular 
bunch of amateurs who have been restoring the 25m Dwingeloo radio 
telescope (http://www.camras.nl). So far we've been able to receive 3 
pulsars (B0329+54, the pulsar in the Crab nebula, and B0950+08). We can 
see single pulses from each of these pulsars. With real-time 
de-dispersion in about 20 MHz of bandwidth, we can even make the single 
pulses of B0329+54 (with a period of 0.7145 seconds) audible trough a 
subwoofer.

Could you do this with a more modest antenna? The lesser gain would need 
to be compensated for by using as much bandwidth as possible (which 
needs de-dispersion), and folding the signal by the pulsar period. 
Folding in turn requires a stable clock, and compensating for the 
doppler shift caused by the Earth's motions. I would say that receiving 
the brightest pulsars is within reach of the bigger EME stations - but 
still working on the calculations (and demonstration) to back this up.

Attached is an image of about 10 minutes of pulsar data we recently 
recorded; folded, but without de-dispersion. It shows the main pulse and 
the less brighter subpulses. The slant of the pulse clearly shows the 
dispersion by the Inter Stellar Medium. You can also see that the pulses 
are brighter at certain frequencies doe to scintillation in the ISM, and 
unfortunately some frequencies are of course affected by RFI. Apologies 
that the labels are in Dutch, but I hope that they are self-explanatory.

Regards, Paul Boven - 73 de PEaNUT
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