[radioastro] Pulsar signal to noise ratio in Radio JOVE, Pulsar nulling in PSR B1112+50
- From: Victor Herrero <hubbleed@xxxxxxxxx>
- To: RadioAstro <radioastro@xxxxxxxxxxxxx>
- Date: Wed, 18 Aug 2010 10:20:51 -0700
Hello Everybody,
Dave T , I mean b), DutyCycle = PulseWidth/PulsePeriod
I think all you can do is search for pulsars that have a large duty cycle,
to optimize your chances.
Going from 0.1 to 0.01 would reduce the S/N by a factor of ~ 0.32.
David F , I think you want to sample at the Nyquist Sampling Theorem rate,
2*Bandwidth.
If you sample less often you are wasting information.
Then the ideal number of samples "on the pulsar" is 2*Bandwidth*DutyCycle,
out of a total 2*Bandwidth samples.
This applies to data reduction in the time domain or in the frequency
domain.
In the time domain you bin the samples so that all the pulsar samples fall
in the same bin.
In the frequency domain, using a Fourier Transform (fast or slow), the
random noise power will be spread over the entire spectrum. The pulsar power
will be concentrated in the fundamental and harmonics of the pulse
frequency.
Leaving aside the RJ Kit, one would like to have an A/D converter of very
high quality with timing synchronized to the GPS system, and use the TEMPO2
software to accurately predict pulse frequency and time.
I think it is better not to detect the radio frequency signal and maintain
coherency in the data processing. This will help to achieve the best
dedispersion of the data. Pulse arrival times depend on the frequency.
Professional work tends to prefer frequency domain processing for
millisecond pulsars, and time domain for second pulsars, but there is no
hard line.
=============================
Change of subject
David, I had forgotten about L bursts !
I agree with the authors that interpret S bursts (millisecond time scale
modulations) as the "pure" radiation of one or a few cyclotron masers.
When many masers are observed at the same time, a near continuum appears amd
we call it L bursting.
Many if not most of the second time scale "bursts" in L radiation are due to
interplanetary modulations caused by the Solar Wind. Ionospheric modulations
are also observed sometimes at minute time scales.
I can provide references about this if anybody is interested.
See also:
http://herrero.freei.me/krausche1976/index.html
http://herrero.freei.me/IonoMod/index.html
Best regards and low interference to all of you,
Victor
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