[time-nuts] Making the most of SRS Rb source

David Forbes dforbes at dakotacom.net
Thu Jan 19 20:21:18 EST 2006

At 2:05 AM +0100 1/20/06, Magnus Danielson wrote:
>From: Mike Nolan <nolan at naic.edu>
>Subject: Re: [time-nuts] Making the most of SRS Rb source
>Date: Wed, 18 Jan 2006 21:58:00 -0400
>Message-ID: <20060119015800.GB8922 at mofongo.naic.edu>
>>  Hi,
>Hi Mike,
>Now, considering that I would like to probe a pulsar what would be the typical
>gear needed? At what frequency do I probe? Just out of curiosity, I don't
>intend to overtrash my VISA card for that purpose, so you can be calm about
>that aspect.
>PS. I should not have bought the GPS clock from that german fellow Heisenberg
>and put the antenna on my house, because either I know where it is 
>but not when
>or I don't know when it is but where. :P


There are several good books available to get you started on pulsars. 
They should be available in the astronomy section of your local 
science library. There are even books out there for amateur radio 
astronomers that show how to use an old satellite TV dish for this 

I think just about any frequency you look at will reveal them. You'll 
need a tunable downconverter to get a decent IF signal a few MHz 
wide. An old satellite tuner set to an astronomy-friendly frequency 
should work, although it will need a motorized equatorial mount or 
computerized alt-azimuth drive system to take long-term data. A bunch 
of amplification is also needed, but this is fairly cheap. Lots of IF 
filtering to keep out bad signals is a must.

The detector is as simple as a diode AM detector feeding an 
integrator feeding an ADC card and a computer data logger. The pulsar 
detection software is available for free on the Internet. The sample 
rate is dependent on the pulse rate you're looking for - the idea is 
to take lots of samples at a regular rate, then have software 'fold' 
them (stack them up at a particular periodic rate) to detect a bump 
in the data which is the pulsar.

The result is a wiggly line on a graph, which is what most radio 
astronomy results look like.

You might also need to know what time it is. I think you can handle that part.


--David Forbes, Tucson, AZ

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