[hpsdr] Radio Astronomy

[hartfuss]

Phil, that would be extremely useful for the kind of measurement 
described. Please keep me informed.
Thanks, Hans, DL2MDQ





Phil Harman schrieb:
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> 
> Most interesting exchange.  One of our group is working on a bandscope 
> that will display up to 55MHz of spectrum. Hope to have it working shortly.
> 
> 73's Phil... VK6APH
> 
> 
> ----- Original Message ----- From: "hartfuss" <hartfuss at ipp.mpg.de>
> To: "Barney Linet" <blinet8 at gmail.com>
> Cc: <hpsdr at hpsdr.org>
> Sent: Thursday, February 05, 2009 5:05 PM
> Subject: Re: [hpsdr] Janus for Radio Astronomy
> 
> 
>> ***** High Performance Software Defined Radio Discussion List *****
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>> Barney, that's very interesting. I would be pleased to see a block
>> diagram of the whole set-up and to get information about the antenne you
>> are using.
>> To measure the 21 cm-line is still on my program for the next years. I
>> also thought to use PowerSDR and it's nice features, however, then also
>> realized the problem with the somewhat too small bandwidth you mentioned.
>> To see the full Doppler-shift when looking into the arms of the galaxy,
>> the bandwidth should be at least 1.5 MHz. Not long ago somebody
>> mentioned her in the reflector that and how (FPGA programming) this
>> should easily be possible with Mercury.
>> A few years ago I already build a down-converter 1420 to 145 MHz with
>> two different LOs to apply frequency hopping and lock-in difference
>> technique to recover the spectral information (line shape) with
>> sufficient S/R, which works. The line then should be scanned by sweeping
>> the frequency of the  2m-receiver.
>> It has, due to other activities, not been completly finished so far.
>> It would be nice to stay in contact.
>> Best 73s, Hans , DL2MDQ.
>>
>>
>> Barney Linet schrieb:
>>
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>>>
>>> ------------------------------------------------------------------------
>>>
>>> As a project, I decided to make a receiver for detecting spectral line
>>> radiation from neutral hydrogen in space. Clouds of cold, rarefied
>>> hydrogen gas far out in space emit radio waves with a frequency of
>>> 1,420.406 Mhz. this well known hydrogen line has been used for the past
>>> 60 years by radio astronomers to map out the structure of the galaxy,
>>> gauge relative speeds of different parts of the galaxy and so forth.
>>> first detected in the late 40's or early 50's it is not easy to put your
>>> finger on. The old-time radioastronomers used huge dish antennas to
>>> collect line radiation for noisy, insensitive
>>> vacuum tube behemoths.they relied on brute force detection (tune to a
>>> single freq, collect energy and integrate.)
>>>
>>> I used more modern components including cascaded LNAs and filters, a
>>> 1420 to 70 MHz image rejection mixer, more cascaded LNAs at 70 MHz, and
>>> a Minicircuits 70 MHz I and Q demodulator. The baseband I and Q signals
>>> are fed to Janus.
>>>
>>> Power SDR includes a spectrum scope which I played with, until I had a
>>> display that showed the spectrum around the magic frequency. At a sample
>>> rate of 192 ksps, the bandwidth is a bit narrow for a neutral hydrogen
>>> radio, this corresponds to a 40 km/sec velocity window. the doppler
>>> shifted line radiation from clouds in the galaxy is more in the range
>>> anywhere from plus-or-minus 250 km/sec. Never the less, nearby
>>> (relatively speaking) clouds will have a limited range of speeds and
>>> stronger radiation. (Stuff farther away is usually moving faster, in
>>> astronomy).
>>>
>>> Well, to make a long story short, I did see features in long time
>>> average (4 sec ) FFT waterfall and spectrum. I dont know if these
>>> features are truly
>>> hydrogen spectral line radiation, but I will continue to investigate.
>>> Another use for an HPSDR! 73's de KC8LTD
>>>
>>>
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