Detecting the Crab pulsar on an old TV

[Marcus D. Leech]

Does anyone know the origins of the mythology about detecting the Crab
pulsar on a B/W TV?   I see it pop up every few years, even among people
who should
  know better (the peak flux of its pulses is only about 5jy, and giant
pulses only occur every few seconds).

If you do the math, there's just no way.    Yet the mythology persists....

[Dave Typinski]

Is the myth about doing this with a TV on a single antenna like a VHF-UHF LPDA
or rabbit ears?

With the TV fed by a large enough antenna array like a VHF or UHF version of the
UTR-2, it might be possible.
--
Dave

[JERRY TAYLOR]

According to ChatGPT here is the origin of the myth

Where the myth came from

There is a real story behind it, but it’s been distorted over time:

• In the 1960s–70s, scientists using modified TV equipment (not an off-the-shelf consumer TV!) detected radio pulses from pulsars.

• They repurposed TV radio IF amplifiers and deflection circuitry in a lab setting to create sensitive receivers.

• This gave rise to the legend that “a TV can pick up the Crab Pulsar.”

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[Marcus D. Leech]

On 2025-11-14 11:06, Dave Typinski wrote:
> Is the myth about doing this with a TV on a single antenna like a
> VHF-UHF LPDA or rabbit ears?

Single small YAGI.

A certain former ERAC prez is pushing this mythology on Facebook right now.

[Captain Anne Flint]

Marcus, 

I remember a fellow talking about it in a BAA meeting 9he had signed in from Hong Kong?). He had long fluffy white hair, as well as a fluffy Persian cat. The other people in the group knew him, but I was new to SARA and really didn’t know many people (or much theory). He said that he had to lay the TV on its side to see the Crab Nebula effect. What a shame - it was such a good story. Wende 

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[Marcus D. Leech]

On 2025-11-14 13:08, Captain Anne Flint wrote:

Marcus, 

I remember a fellow talking about it in a BAA meeting 9he had signed in from Hong Kong?). He had long fluffy white hair, as well as a fluffy Persian cat. The other people in the group knew him, but I was new to SARA and really didn’t know many people (or much theory). He said that he had to lay the TV on its side to see the Crab Nebula effect. What a shame - it was such a good story. Wende

The only *possible* detection here would be on the giant pulses from the crab--which happen at a rate of 0.3 to 1Hz (approximately).  I don't know that
  much about the brightness distribution among the giant pulses, but let's consider a 5000Jy pulse.

The PSD (power spectral density) of a 5000Jy pulse is about -192dBm/Hz, and we'll assume an antenna with a 1 m**2 aperture, to make the
 math simpler.  Let us also assume a reasonably "modern" LNA of 0.5dB NF, which means that the equivalent noise PSD is about -176.5dBm/Hz.
 Since we aren't really doing much in the way of integration, because of the requirements of the "dot clock" of an NTSC receiver, we're stuck
 with a roughly -15.5dB SNR deficit, even when processing "giant" pulses from the Crab, which arrive lined-up with the pulse period, but with
 "missing" pulses.    Now, with ordinary pulsar processing, you "make up" for the SNR deficit by doing "folding" or synchronous detection--you
  overlay many hundreds/thousands of pulses on top of one another, so that the noise variance goes to zero, and the average pulse profile
  "pops up" out of the noise.

I don't think an NTSC/PAL receiver can achieve this, unless it is modified considerably.

The last time I watched the Crab Nebula in "real time" was at Algonquin Radio Observatory, with their 47m dish, with a prototype
  CHIME receiver, with 400MHz-wide waterfall type display, without ANY folding.   The ordinary pulses were not visible (even on a 47m dish!),
  but the giant pulses showed up on an irregular basis on a timescale of a second or two.   The *super* giant pulses showed up a few times a day,
  and the miserable grad students had to *manually* watch the display for hours and hours, and take not of super-giants.

I would invite others to look at my analysis.  But I'm pretty-sure this is still in the "mythology" department.  But, reiterating, if you allow modifications
  to the receiver of an arbitrary degree, then yeah, sure.  You could basically use a TV as a display device to a purpose-built receiver for the
  Crab Pulsar.

The frame-rate for NTSC is 29.97Hz, which is quite close to the pulse rate of the Crab, but being "sloppy close" in small-antenna pulsar processing
  is generally nowhere near good-enough in my experience.  The frame-rate for PAL is 25Mhz, which is quite far away from the Crab pulsar
  pulse rate of 29.48Hz.

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[Captain Anne Flint]

Hey Marcus, 

Maybe if you contact Paul Hearn (or another one of those guys) he and/or they can tell you who the man was … like in a game of Clue: 

• with the cat 
• in a garden shed 
• in the Far East 

I was just so charmed by the image (the cat would jump up on his laptop, he’d pet the cat, the fluffy cat hair would float, hanging suspended in the air) that I wasn’t paying much attention to what he was saying, or his name. I thought he was a regular member, but I haven’t seen him since; it was my first BAA RA meeting. 

Keep in mind that, here in Texas, a well-told tale can be an art form. Unless you are actually looking for factual information! and then it’s just annoying. 

I’m sure that you are right, unless the man was on the original development team? or he just thought it was an amusing idea? Anyway, I hope you find out more. 

Wende 

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[Steve Berl]

I wonder how hard it would be to modify whatever oscillator was generating the frame rate of the TV from 29.97Hz to 29.48Hz? That might make it pop up?

In old school Tv sets was it typically some sort of crystal controlled thing, or was it derived from something in the received TV signal, or something else?

Steve

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--

-steve

[Marcus D. Leech]

On 2025-11-14 20:26, Steve Berl wrote:

I wonder how hard it would be to modify whatever oscillator was generating the frame rate of the TV from 29.97Hz to 29.48Hz? That might make it pop up?

In old school Tv sets was it typically some sort of crystal controlled thing, or was it derived from something in the received TV signal, or something else?

Steve

I can't remember, TBH.     I think it was timed from the incoming signal---there was a Vertical Blanking Pulse that synchronized the framing, but the TV had its own
  framing generator that was "dragged around" by the blanking pulse.  But, well, it has been a great many years since I looked at that..

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[fasleitung3]

What may have contributed to the myth is this article:
https://www.nature.com/articles/2211037a0
The title is certainly misleading. The full article is behind a
paywall, but I understand this is about the observation of the optical
pulsation with an optical telescope and displaying things on a TV.
It has nothing to do with radio observations.
Wolfgang

> --

[Alex P]

See if this link works 

https://sci-hub.se/10.1038/2211037a0

Cheers,

Alex P

[fasleitung3]

This website uses a wrong certificate, so I am not inclined to access it.

Wolfgang

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[b alex pettit jr]

Here is page 1 of 2

[Eduard Mol]

Many years ago a friend of mine brought a 70(?) cm loop antenna and some radio equipment to an astronomy camp. He also had it connected to a small old CRT tube TV. Indeed he picked up a pulsating signal, thinking that it was the Vela pulsar. Even though I did not know anything about radio astronomy back then I was skeptical about this, because Vela always stays well below the horizon at our latitudes. Later on we concluded that it was probably just RFI from an electric fence…

Op za 15 nov 2025 om 12:46 schreef 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Here is page 1 of 2

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[fasleitung3]

Thanks Alex,

so indeed it is a TV camera connected to an optical telescope with some enhancement in between.

Nothing to do with radio, let alone using a TV set as receiver.

But one can imagine that the title can mislead some people.

Best regards,

Wolfgang

Am Samstag, den 15.11.2025, 11:46 +0000 schrieb 'b alex pettit jr' via Society of Amateur Radio Astronomers:

Here is page 1 of 2

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[Alex P]

Page #2

[Captain Anne Flint]

Thanks, Alex! Wende 

On Nov 15, 2025, at 7:03 AM, 'Alex P' via Society of Amateur Radio Astronomers <sara...@googlegroups.com> wrote:

Page #2

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<Crab_TV_page2.jpg>

[Jim Sky]

This was a fun thread!  I may have repeated that myth at some point in the past, hopefully I never published it.   If it were possible to do this at radio, I did always think it would only be a speck like any other in a snowy off-channel screen and so you would never know you had seen it.  Marcus's calculation even rules this out, and he was being generous with the burst strength.