Detection of Pulsars at Low Frequencies - Reality Check... :-(

[Steve Olney - VK2XV]

See...

http://pulsar.vk2xv.net/n9_reality_check.htm

Steve VK2XV

[Dave Typinski]

Hi Steve,

VERY nice job!

You have arrived at pretty much the same figures I and two others did in 2010.
Glad to see we agree. That's a good reality check on our mathematics.

Two years assumes a fairly hot pulsar. For less powerful pulsars, you would
have to fold not mere years, but centuries of 20 MHz Radio Jove data.

Would you consider writing up your efforts in Word doc format for submission to
the SARA journal?
--
Dave

[David L, N5OIQ]

Steve,

I also enjoyed the pulsar information on your website and your calculations.  I particularly like the reality check you provided which really drives home the point that pulsar detection isn't easy and with a single dipole and narrow bandwidth, even the strongest will be undetectable in any reasonable length of time.

I'm on a quest to detect pulsars myself and realized that software defined radios could be a valuable new tool to detect them.  I began testing in the 30 to 50 MHz range using a QS1R software defined radio with a 2.5 MHz bandwidth. Compared to 2.4 kHz bandwidth, one should expect a (2500000/2400) = 1041x = 30 dB improvement in sensitivity which in itself would make up the gap from the Reyes effort.  Of course, dedispersion would be needed, but I think it is certainly doable, particularly if incoherent dedispersion is applied which can be crunched computationally with a decent desktop computer.  

RTLSDR dongles could be a really cheap alternative to higher cost SDRs (and even conventional receivers) that also have some serious bandwidth.  I've played around with a couple of these things and while their internal clock is pretty unstable, I would imagine that if you used a series of FFT-based pulsar detection method instead of epoch folding (after dedispersion), that they might have good enough stability.  

The other way to make up the gap on the Reyes effort is on the antenna side by combining dipoles in phase.  I phased 16 inverted V antennas together cut for 50 MHz which gives ~20 dBi gain versus 8.16 dB for a single antenna.   The LOFAR group can detect pulsars with arrays of 96 inverted V's (see link below), so I think pulsar detections are achievable at the amateur level.  The LOFAR group has a lot of information about sky noise limiting performance at low frequencies which I found interesting.  Basically, one doesn't need to even have their dipole matched at low frequencies so broadband performance is easy to come by a low frequencies.

However, my experience has been frustrated by some serious RFI issues in my suburban environment, so getting out to a remote location will be key.  At 50 MHz, RFI was absolutely terrible for me, at 150 MHz it was better but still too severe and at 408 MHz, conditions are much better, but still probably too poor to make any progress.  My feeling is that if you can't see a noise floor rise from the galactic plane passing through your antenna beam, things will not work out.  

David

Low frequency array of simple dipoles (inverted V antennas) if you have enough space:  http://www.astro.rug.nl/~peletier/15%20LBA_ADD.pdf

[Marcus D. Leech]

On 11/28/2012 10:14 AM, David L, N5OIQ wrote:
>
>
> I'm on a quest to detect pulsars myself and realized that software
> defined radios could be a valuable new tool to detect them. I began
> testing in the 30 to 50 MHz range using a QS1R software defined radio
> with a 2.5 MHz bandwidth. Compared to 2.4 kHz bandwidth, one should
> expect a (2500000/2400) = 1041x = 30 dB improvement in sensitivity
> which in itself would make up the gap from the Reyes effort. Of
> course, dedispersion would be needed, but I think it is certainly
> doable, particularly if incoherent dedispersion is applied which can
> be crunched computationally with a decent desktop computer.

Coherent de-dispersion is also possible, but perhaps not in real-time
when the observing frequency is below about 100MHz, and there's
significant bandwidth. My IRA software includes coherent
de-dispersion in real-time, but the filters get unreasonably large at lower
frequencies.

>
> RTLSDR dongles could be a really cheap alternative to higher cost SDRs
> (and even conventional receivers) that also have some serious
> bandwidth. I've played around with a couple of these things and while
> their internal clock is pretty unstable, I would imagine that if you
> used a series of FFT-based pulsar detection method instead of epoch
> folding (after dedispersion), that they might have good enough stability.

The phase-noise on these devices is less than wondeful. But the drift
issue can be dealt with using passive thermal-control techniques.
If you encapsulate the dongle in insulation inside a metal box, the
LO drift becomes negligible.

>
> The other way to make up the gap on the Reyes effort is on the antenna
> side by combining dipoles in phase. I phased 16 inverted V antennas
> together cut for 50 MHz which gives ~20 dBi gain versus 8.16 dB for a
> single antenna. The LOFAR group can detect pulsars with arrays of 96
> inverted V's (see link below), so I think pulsar detections are
> achievable at the amateur level. The LOFAR group has a lot of
> information about sky noise limiting performance at low frequencies
> which I found interesting. Basically, one doesn't need to even have
> their dipole matched at low frequencies so broadband performance is
> easy to come by a low frequencies.

The very first pulsar detections were made with an antenna array
covering many hectares.

>
> However, my experience has been frustrated by some serious RFI issues
> in my suburban environment, so getting out to a remote location will
> be key. At 50 MHz, RFI was absolutely terrible for me, at 150 MHz it
> was better but still too severe and at 408 MHz, conditions are much
> better, but still probably too poor to make any progress. My feeling
> is that if you can't see a noise floor rise from the galactic plane
> passing through your antenna beam, things will not work out.
>
>

Moving to higher frequencies has some distinct advantages:

o easier to use wider bandwidths, both due to RFI considerations,
and coherent de-dispersion in real-time is possible
o easier to get significant antenna gain at higher frequencies,
without using your entire neighbourhood for antennas

The main disadvantage is that pulsar power tends to decrease with
increasing frequency--since this is effectively
synchrotron radiation, it'll have a higher intensity at lower
frequencies.



--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org

[Steve - VK2XV]

David,

>
> I also enjoyed the pulsar information on your website and your
> calculations. I particularly like the reality check you provided which
> really drives home the point that pulsar detection isn't easy and with a
> single dipole and narrow bandwidth, even the strongest will be
> undetectable
> in any reasonable length of time.
>

Thanks - even though I primarily write it up for as an exercise for own my
benefit it is pleasing to know others are getting some use out of the
effort.

>
> I'm on a quest to detect pulsars myself and realized that software defined
> radios could be a valuable new tool to detect them. I began testing in
> the
> 30 to 50 MHz range using a QS1R software defined radio with a 2.5 MHz
> bandwidth.
>

Sounds interesting. I am not currently 'into' SDRs (as Joe Walsh says -
'I'm an analog man"...) but I look forward to learning about them -
especially for RA.

>
>Compared to 2.4 kHz bandwidth, one should expect a
> (2500000/2400) = 1041x = 30 dB improvement in sensitivity which in itself
> would make up the gap from the Reyes effort.
>

Using narrow bandwidth of 2.4KHz is a major handicap for sure, but a
restriction due to dispersion as you say.

Unfortunately going from 2.4kHz to 2.5MHz only gains you ~15dB - not 30dB.
It's that ever present square root nuisance.

.
>
> I've
> played around with a couple of these things and while their internal clock
> is pretty unstable, I would imagine that if you used a series of FFT-based
> pulsar detection method instead of epoch folding (after dedispersion),
> that
> they might have good enough stability.
>

What short/long term stability did you find ? 10ppm would be fine for 4
hours observation for pulsars near 1Hz.

>
> The other way to make up the gap on the Reyes effort is on the antenna
> side
> by combining dipoles in phase. I phased 16 inverted V antennas together
> cut for 50 MHz which gives ~20 dBi gain versus 8.16 dB for a single
> antenna.
>

Unfortunately such an array would require a divorce first if put on our 3/4
acre block.... :-)

>
> The LOFAR group can detect pulsars with arrays of 96 inverted
> V's (see link below), so I think pulsar detections are achievable at the
> amateur level. The LOFAR group has a lot of information about sky noise
> limiting performance at low frequencies which I found interesting.
> Basically, one doesn't need to even have their dipole matched at low
> frequencies so broadband performance is easy to come by a low frequencies.
>

Yes - I have examined the LOFAR work and was encouraged, but the complexity
of the antenna is a little too high. With increasing gain comes narrower
beamwidth. Unless it can be electronically steered the extra gain is
effectively halved due to the shorter time in the beamwidth. This can be
minimised by narrower the beamwidth in declination and keeping the RA
beamwidth wide. Unfortunately there is nowhere that orientation would fit
in this 'backyard astronomer's' backyard (even after a divorce...).

>
> However, my experience has been frustrated by some serious RFI issues in
> my
> suburban environment, so getting out to a remote location will be key. At
> 50 MHz, RFI was absolutely terrible for me, at 150 MHz it was better but
> still too severe and at 408 MHz, conditions are much better, but still
> probably too poor to make any progress. My feeling is that if you can't
> see a noise floor rise from the galactic plane passing through your
> antenna
> beam, things will not work out.
>

Agreed - RFI is a killer. Doing a drift scan here at 45MHz shows lots of
intermittent RFI spikes as well as step jumps. The galactic hump is there
but it needs a number of days integrating to get a reasonable curve. One
way of cleaning up the curve would be instead of averaging successive days,
take the minimum reading across the days for each sample point. This would
eliminate many RFI spikes if they were randomly occuring. I think I read
somewhere a paper of someone coming up with this idea already so I am
certain it is not new.

Cheers

Steve VK2XV

[Marcus D. Leech]

On 11/28/2012 02:34 PM, Steve - VK2XV wrote:
>
>
> What short/long term stability did you find ? 10ppm would be fine
> for 4 hours observation for pulsars near 1Hz.
>

Unfortunately, these things use cheap computer-grade XTALs, about
100PPM. But my experience is that with thermal control of
the device, the long-term frequency stability gets vastly better.
For pulsars, absolute frequency accuracy isn't nearly as important
as long-term stability and phase noise. They use an awkward master
crystal -- 28.8MHz. But if you had a high-quality source of
28.8MHz, you could use that to drive these things instead of the
on-board crystal.

[Steve - VK2XV]

G'day Marcus,

>
> Unfortunately, these things use cheap computer-grade XTALs, about 100PPM.
> But my experience is that with thermal control of
> the device, the long-term frequency stability gets vastly better. For
> pulsars, absolute frequency accuracy isn't nearly as important
> as long-term stability and phase noise. They use an awkward master
> crystal -- 28.8MHz. But if you had a high-quality source of
> 28.8MHz, you could use that to drive these things instead of the
> on-board crystal.
>

Are other receiver-like parameters specified (NF, IMD, gain stability, etc.)
specified for these devices ?

Are they good quality comms devices or is the main attraction bandwidth +
DSP ?

Steve

[Steve - VK2XV]

Dave,

Thanks.

>
> You have arrived at pretty much the same figures I and two others did in
> 2010. Glad to see we agree. That's a good reality check on our
> mathematics.
>

It is not the result I wanted to get - but that's life (and pulsar hunting).

>
> Would you consider writing up your efforts in Word doc format for
> submission to the SARA journal?
>

I don't really think there is anything novel done here to report - it only a
description on my stumbling steps (hopefully forward). I am a newbie to RA
and especially pulsars, so for the time being I will stick to learning from
others and improving my understanding.

Maybe when I am successful at detecting a pulsar signal it would be
appropriate.

Cheers

Steve

[Marcus D. Leech]

On 11/28/2012 02:54 PM, Steve - VK2XV wrote:
>
>>
>
>
> Are other receiver-like parameters specified (NF, IMD, gain stability,
> etc.) specified for these devices ?

I guffaw heartily in your general direction :-) The two most popular
receivers that are coupled with the baseband/bridge chip
are the Elonics E4000 and Rafael Micro R820T. Good luck finding
data. But the NF of these is about 5dB, which given their
broad tuning range is not bad. The gain stability is more than
adequate for radio astronomy.

>
> Are they good quality comms devices or is the main attraction
> bandwidth + DSP ?
>

These devices (RTLSDR) are marketted as DVB-T dongles in parts of the
world where DVB-T is a "thing" they have a semi-secret mode
where the on-board DVB-T demodulator is bypassed, sending decimated
I/Q samples towards the host at up to 3.2Msps.

They're about $10-$15.00 each on eBay and similar sites.

[Steve - VK2XV]

Marcus,

Thanks.

> I guffaw heartily in your general direction :-) The two most popular
> receivers that are coupled with the baseband/bridge chip
> are the Elonics E4000 and Rafael Micro R820T. Good luck finding data.
> But the NF of these is about 5dB, which given their
> broad tuning range is not bad. The gain stability is more than adequate
> for radio astronomy.

I did a brief search and it looks like I will leave this for later. There
seems a lot to be learnt for driving them (as well as being an 'analog man',
I am an XP + C# coder...)

Cheers

Steve

[Marcus D. Leech]

On 11/28/2012 03:31 PM, Steve - VK2XV wrote:
>
> I did a brief search and it looks like I will leave this for later.
> There seems a lot to be learnt for driving them (as well as being an
> 'analog man', I am an XP + C# coder...)
>
> Cheers
>
> Steve

There's a guy called "prog" who hangs out on ##rtlsdr who is a C# guy --
he wrote SDR# which is a multimode receiver app that works with
these Dongles.

I used Gnu Radio exclusively, and I have a simple RA application up on
CGRAN. But I don't know anyone who has made simple_ra work
on Windows. I might be considered an elitist snob, but since 90% of
professional science is conducted with Linux tooling, I think there's
a useful lesson there...

[Steve - VK2XV]

Marcus,

>
> I might be considered an elitist snob, but since 90% of
> professional science is conducted with Linux tooling, I think there's
> a useful lesson there...
>

Elitist snob ? No - sounds more like commonsense to me.

Cheers

Steve

[David L, N5OIQ]

Steve,

Oops, your right about the bandwidth issue (delta Tsys = Tsys/sqrt(B x tau) ), thanks for spotting that. Still, the 15 dB is worth going after.  In terms of integration time, the 1000x advantage will hold.

Those dongles have greater than 100 ppm stability from my own experience which would be a headache.  They also have an 8 bit sampling depth which will limit their dynamic range.  They have their limitations, but could be a nice gateway to Gnuradio and more serious SDRs like the USRP N210.

I don't think a full LOFAR LBA would be needed either.  You could go with a dipole, then two, then four, etc. until your better half puts her foot down.  I was able to get up to 16 before my wife stopped me.  If you can see a galactic hump at 45 MHz you are fortunate indeed, and with an SDR, perhaps you might be able to zap RFI in the digital domain (see the last topic post of mine).

Yes, steering an array is an issue, but by swapping in different coax lengths, different declinations could be achieved.  The value of keeping off target radiation out of the antenna beam should make up for the reduced time that the target is in the beam.

David

[Marcus D. Leech]

On 11/28/2012 04:13 PM, David L, N5OIQ wrote:
> Steve,
>
> Oops, your right about the bandwidth issue (delta Tsys = Tsys/sqrt(B x
> tau) ), thanks for spotting that. Still, the 15 dB is worth going
> after. In terms of integration time, the 1000x advantage will hold.
>
> Those dongles have greater than 100 ppm stability from my own
> experience which would be a headache. They also have an 8 bit
> sampling depth which will limit their dynamic range. They have their
> limitations, but could be a nice gateway to Gnuradio and more serious
> SDRs like the USRP N210.

The 8-bit sampling depth is utterly irrelevant for RA uses. The only
time it's an issue is if there are blocking signals that would exceed your
ADC dynamic range. But in RA, one generally uses good RF "hygiene"
to avoid such blocking issues. The "big boys" often use 1 or 2-bit
ADCs. They have 100PPM *accuracy*, but when thermally-managed, they
drift very little. For pulsar work, you don't care whether
the tuned frequency is a few kHz "off" from where you think it is.

Consider that at VHF, the galactic-plane constitutes roughly 1-2dB above
the ambient sky noise.

>
> I don't think a full LOFAR LBA would be needed either. You could go
> with a dipole, then two, then four, etc. until your better half puts
> her foot down. I was able to get up to 16 before my wife stopped me.
> If you can see a galactic hump at 45 MHz you are fortunate indeed,
> and with an SDR, perhaps you might be able to zap RFI in the digital
> domain (see the last topic post of mine).

A couple of summers ago, I ran a riometer in my backyard here. I was
getting galactic-plane transits every day at 38.5Mhz with an SDR-based
system operating over about 700kHz bandwidth. Then the
gosh-darned-horrible-sons-of-one-eyed-prairie-dog city planning people
swapped
out the existing street lights for these new RF-pumped inductive
fluorescent street lamps. Wipes out big chunks of HF VHF at night.

[David L, N5OIQ]

Marcus,

I can reduce bit depth on my SDR for neutral hydrogen work at 1420 MHz to 1 or 2 bits, but at lower frequencies, I'm getting some very strong signals in my pass band that a 1 or 2 bit sampling ADC wont handle.  The LOFAR group is using a 12 bit sampling depth to achieve the dynamic range they need.

I've got the RF pumped inductive street lamps and CFLs in the house are pretty bad also.

David

[Marcus D. Leech]

On 11/28/2012 04:35 PM, David L, N5OIQ wrote:
> Marcus,
>
> I can reduce bit depth on my SDR for neutral hydrogen work at 1420 MHz
> to 1 or 2 bits, but at lower frequencies, I'm getting some very strong
> signals in my pass band that a 1 or 2 bit sampling ADC wont handle.
> The LOFAR group is using a 12 bit sampling depth to achieve the
> dynamic range they need.
>
> I've got the RF pumped inductive street lamps and CFLs in the house
> are pretty bad also.
>
> David
>

Indeed, if your front-end is as wide as a New Orleans Street Lady on a
Saturday Night, you'll need more bits, and LOFAR are taking that approach
with their RF.

I was easily able to do riometry with a simple 25Mhz to 45Mhz filter and
8-bit sample depth a couple of summers ago. Until, as I said, the
RF pumped street lamps arrived. They made my life horrible--even at
mid VHF frequencies. The ones they use here are nominally 210kHz
pumped, but the oscillators aren't very sophisticated or stable, so
they really put spectral components all over the place.

[Steve - VK2XV]

Marcus,

>
>For pulsar work, you don't care whether
> the tuned frequency is a few kHz "off" from where you think it is.
>

Certainly it doesn't matter whether the pre-detection frequency accuracy is
off a bit. After all it doesn't matter much if you are receiving at 45.0MHz
or 45.1MHz. But it certainly matters that the sampling rate is accurate
to at least 20ppm for FFT and a few ppm for epoch folding (unless you want
to go period hunting). Drift of a few ppm over a 4 hour observation run
would be a killer. You would need a timing signal recorded along with the
data to track it.

Steve

[Marcus D. Leech]

Yes, you're correct. I forgot about the matching sample-rate-offset
that comes with having a 100PPM master oscillator.

[Marcus D. Leech]

On 11/28/2012 05:15 PM, Steve - VK2XV wrote:
>
>

> Certainly it doesn't matter whether the pre-detection frequency
> accuracy is off a bit. After all it doesn't matter much if you are
> receiving at 45.0MHz or 45.1MHz. But it certainly matters that the
> sampling rate is accurate to at least 20ppm for FFT and a few ppm for
> epoch folding (unless you want to go period hunting). Drift of a
> few ppm over a 4 hour observation run would be a killer. You would
> need a timing signal recorded along with the data to track it.
>
> Steve

If you can characterize your frequency offset, and it's stable, then you
just wire that in to the folding algorithm. The main thing is stability.
Even these cheap crystal XOs are OK when made thermally stable.

[Steve - VK2XV]

Marcus,

>
> If you can characterize your frequency offset, and it's stable, then you
> just wire that in to the folding algorithm.
>

Yes - I already do this by using the 1 second pips of WWV (see website).

I have a Rb fs here - but that is a little less common (and not cheap).
The approach I would take would be to record a 1pps output from a cheap GPS
unit ($70) on a second channel to track the sampling rate (same technique as
Fernando used back in the days of analog tape recorders). I much prefer
that method instead of triggering A/Ds by a clock harmonically related to
the target signal period - too much opportunity to get artifacts for my
liking as I discovered many moons ago with terrestrial radio experiments.

Looks like I will be heading up band....

Cheers

Steve

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[Marcus D. Leech]

On 11/28/2012 07:27 PM, Steve - VK2XV wrote:
> Marcus,
>
>>
>> If you can characterize your frequency offset, and it's stable, then
>> you just wire that in to the folding algorithm.
>>
>
> Yes - I already do this by using the 1 second pips of WWV (see website).
>
> I have a Rb fs here - but that is a little less common (and not
> cheap). The approach I would take would be to record a 1pps output
> from a cheap GPS unit ($70) on a second channel to track the sampling
> rate (same technique as Fernando used back in the days of analog tape
> recorders). I much prefer that method instead of triggering A/Ds by
> a clock harmonically related to the target signal period - too much
> opportunity to get artifacts for my liking as I discovered many moons
> ago with terrestrial radio experiments.
>
> Looks like I will be heading up band....
>
> Cheers
>
> Steve
>

If you have a bit of engineering skill, you can use the Rb reference to
produce the master clock for your SDR, at whatever frequency it uses.

There are a few generic synthesizer boards out there that take a 10Mhz
standard reference in, and produce a wide range of programmable
clock frequencies out.

[Dave Typinski]

On 11/28/2012 15:02, Steve - VK2XV wrote:
>
>> Would you consider writing up your efforts in Word doc format for submission
>> to the SARA journal?
>
> I don't really think there is anything novel done here to report - it only a
> description on my stumbling steps (hopefully forward). I am a newbie to RA and
> especially pulsars, so for the time being I will stick to learning from others
> and improving my understanding.
>
> Maybe when I am successful at detecting a pulsar signal it would be appropriate.

Well, I for one think it's entirely appropriate as-is in the spirit of a good
Shakespearean tragedy. Tales of null results, line noise, and impossible
numbers are just as important as the tales of verified observations. I enjoy
reading more about the way things so often /really/ go than the polished
articles that present an observation as a fait accompli where the author appears
to have done a perfect experiment from start to finish.
--
Dave

[Marcus D. Leech]

In that case, I should do a "Ken Tapping is right" article. Backyard
Radio Astronomy below 1GHz or so is futile :-)

[Dave Typinski]

On 11/28/2012 19:56, Marcus D. Leech wrote:
>>
> In that case, I should do a "Ken Tapping is right" article. Backyard Radio
> Astronomy below 1GHz or so is futile :-)

So is resistance. ;)
--
Dave

[Marcus D. Leech]

With enough voltage resistance isn't futile :-)

[Robert Hart]

Lots of if's here just dreaming.

I was looking at http://www.ergotelescope.org/ the other day and
wondered if similar could be done in radio astronomy. Like a cheap
wideband open-source SDR could be developed for the amateur radio guy,
that has a GPS sync local oscillator and a reasonable quality Analogue
to digital converter say a few mhz so they could be purchased or built
all around the world.

Then if someone could develop some software that monitored the signal
looking for "interesting" observations. When it did, it would upload
the time stamp file to too a cloud server where it could correlate
against many similar observations across the world.

Robert

[Don Donigan]

Wow! I like that dreaming!

I can provide the cloud infrastructure, and do software development on that side.

Don

Best regards,

Don Donigan

There's no place like ~/
Consulting Computer Scientist
Donigan Technology, LLC
http://dondonigan.com
Mobile: (575) 420-4692 (voice and SMS)

Robert

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[Marcus Leech]

So you guys do know about the RASDR project that SARA is funding, yes?

sara-list-...@googlegroups.com

[Robert Hart]

No is there a link?

On 30/11/2012 6:38 AM, Marcus Leech wrote:

[WILLIAM & MELINDA LORD]

Hi Guys,

The group working on the SARA RASDR project have a report in the last several SARA Journals. If you are a current member you can go to the Journal link and read more about the project and progress.

 

Bill & Melinda Lord
www.tnSkyNet.com
www.radio-astronomy.org

Light travels faster than sound. This is why some people appear bright until you hear them speak. :-)

---

From: Robert Hart <rob...@hardhack.org.au>
To: sara...@googlegroups.com
Sent: Thursday, November 29, 2012 2:58 PM
Subject: Re: [SARA] A crowd sourced worldwide amateur radio telescope.

[Myamiphil]

here's a PDF.... do search on Google...several articles

 

Best Regards

Phil

---

From: Robert Hart <rob...@hardhack.org.au>
To: sara...@googlegroups.com

Sent: Thursday, November 29, 2012 3:58 PM

Subject: Re: [SARA] A crowd sourced worldwide amateur radio telescope.

[Clint Jeffrey]

Hello Steve,

                     Just curious, I'm having trouble opening links, are they working?....for example I get "can't reach page"...

Cheers

Clint - VK3CSJ

On Wednesday, November 28, 2012 at 6:26:30 PM UTC+11 Steve Olney - VK2XV wrote:

See...

http://pulsar.vk2xv.net/n9_reality_check.htm

Steve VK2XV

[Clint Jeffrey]

Okay....just noticed the year on that email was 2012!....I have no idea why I'm seeing mail from 14 years ago. 

Please ignore.....;)

Clint - VK3CSJ

---

From: sara...@googlegroups.com <sara...@googlegroups.com> on behalf of Clint Jeffrey <vk3...@gmail.com>
Sent: Thursday, 16 July 2026 8:49 PM
To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: [SARA] Re: Detection of Pulsars at Low Frequencies - Reality Check... :-(

 

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