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Hey, turn down that radio, it's alien season and we're hunting aliens

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Facepalm

Won't work

See Cosmic background noise vs Frequency (rises sharply as frequency reduced), Shannon's Law (Information) and Inverse Square Law. Also dish gain is related to the cube of frequency, thus 1/10th frequency gives 1/1000th gain on same size dish.

Only spectroscopic analysis is likely to give results, starlight affected by planetary transits. Radio is good only to a few light years or a bit more if someone is pointing THEIR massive array with Gigawatts of power at us.

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Trollface

Re: Won't work

SETI Institute waited to be told by some commentard.

So done!

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Re: Won't work

Yes, that thing you thought of in a few moments reading a page on the internet, the SETI boffins won't have thought of that for sure.

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Pint

Re: Won't work

Once upon a time, an edition of a radio communications magazine published advice to try the technically challenging EME (Moonbounce) communications in the 160m band (1.8 MHz).

"Fewer Wavelengths to the Moon" ...

...was the logical basis, as per the well known 'Pathloss Equation' (the one with 32.45 dB, etc.). Lower frequency = less pathloss.

Yep. It was the April edition.

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Re: Won't work

Check your maths. Swings and roundabouts on antennas and path loss vs frequency.

Gain for a given antenna aperture area is proportional to frequency squared, not cubed. Note this is area, not diameter.

However pathloss over a given distance is proportional to frequency.

The reason to go up in frequency traditionally has been to avoid noise, terrestrial as well as galactic.

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Boffin

Re: Won't work - Dish gain

Dish gain only really helps you if you know where to look. The advantage of arrays like the MWA is that they can make multiple phased-arrays, scanning in multiple directions simultaneously.

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Pint

Re: Won't work

HL, it's not exactly "swings and roundabouts" if it's square vs. proportional.

Just sayin'. :-)

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Anonymous Coward

Re: Won't work

OP - NM the trolls that don't know anything there isn't an app for, those of us involved in radio know how valid your concerns are.

Fortunately, noise cancellation is somewhat an easy process with differential samples. Doesn't take care of everything, but does make the S/N ratio go on par with the noise temp of the LNA.... THAT is still a serious problem even with cryogenics at ground level.

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Pint

Re: Won't work

GG "...make the S/N ratio go on par with the noise temp of the LNA..."

At HF and below, the noise is set by the external environment. At UHF and above, it's pretty much down to the NF of the LNA. At VHF (e.g. 100 MHz), it's the area of transition. As LNAs have gotten better over the years, the 'crossover' has drifted upwards. These days, at VHF (the subject here), it isn't all that difficult to get into the external noise.

Even nearly 30 years ago, met a guy that was into the external noise at UHF. The Sun passing across his 20-foot dish caused a big noise peak. NF less than a half dB. A long time ago.

~40 years in Comms. (Geesh, I'm closer to death than that.)

Cheers.

__... ...__

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Re: Won't work

Jeffy poohs, It is swings and roundabouts if you include path loss, as you'll see I specificallly mentioned.

However as I also mentioned, going down in frequency also increases the ambient noise floor.

But then making very low noise receivers is easier at lower frequencies.

But then your beam width increases with lower frequency, so more noise.

But then increased beam width means more simultaneous coverage.

But then wider coverage area means more difficult to pinpoint the source.

Lots of swings and roundabouts, but my main point was around the size of the antenna aperture combined with path loss, and all other things being equal means that the change in gain due to frequency is offset by the change in path loss. It's all part of an RF link budget calculation.

Just sayin' ;-)

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Anonymous Coward

FFS

can't SETI just trot over to Edwards Air Force Base, and ask someone there if they're wasting their time?

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Re: FFS

"I can neither confirm nor deny that you are wasting your time, sir."

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Alien

Re: FFS

Yes, you are wasting your time, by coming here and asking me... among other reasons.

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Coat

I for one

Welcome our low frequency overlords.

had to be done.

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Re: I for one

And I for one would like to ask them, or one of their boffin friends, why they call it the Low Frequency Array when it operates in the VHF band (Very High Frequency).

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Re: I for one take 2

Well looking at frequencies in the MHz range as opposed to the GHz range is I suppose relatively long wavelength.

I am not very good with radio propagation but very long wavelength (on the order of KHz) bounces off the ionoshere so I presume that just as SW radio can travel round the world any incoming SW would bounce back out into space.

I am going to fit the boat with an HF with a pactor modem set at some point so will have to learn more about all that sort of stuff.

Beer because it is nearly time.

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Pint

Re: I for one take 2

@RK

First tidbit: kHz, not KHz.

:-) !!!

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Re: I for one take 2

"I am not very good with radio propagation but very long wavelength (on the order of KHz) bounces off the ionoshere so I presume that just as SW radio can travel round the world any incoming SW would bounce back out into space."

That depends on the MUF (stop sniggering at the back!) - or Maximum Usable Frequency. See:

http://www.spacew.com/www/realtime.php

The MUF changes over the course of the day, and over the course of the seasons. It is governed by the plasma levels in the ionosphere. A lot of energy, as we see during sun-spot maxima, creates a lot of plasma, and the ionosphere can become refractive right up to 30MHz. During minima, the MUF is quite low, and you'll find all us Radio Amateurs hanging out below 14MHz. Most of the time, the MUF allows frequencies at the higher end of the HF spectrum (and at VHF, and above) to radiate into space. That is why NASA/JPL powered-up Juno's 28MHz receivers and asked volunteers to blast as much man-made radio energy at the probe as we could - all timed to transmit at the same time.

It will be interesting to see if SETI can come up with anything at those VHF frequencies - other than noise and Pulsars...

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Pint

Re: I for one take 2

TE "...the MUF is quite low..."

Yes, it can be.

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Re: Low, very high, frequencies

The radioastronomy boffins say that useful results from terrestrial observations have been obtained at frequencies from 2 MHz to 1 000 GHz and above.

All I suggested is that they should use the appropriate ITU band designation (VHF) instead of writing the first thing that came into their heads.

After all it is the ITU that coordinates the world-wide protection from terrestrial interference for the radioastronomy frequencies.

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This post has been deleted by its author

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Re: I for one

"And I for one would like to ask them, or one of their boffin friends, why they call it the Low Frequency Array when it operates in the VHF band (Very High Frequency)."

Astronomers have a different sense of scale. Hence the local group (of galaxies).

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Re: I for one

VHF is called "low frequency" due to a historical oddity. In the early days of radio the frequencies used were quite low. The technology level required for radio goes up with frequency, so the lowest freaks were all they could manage. That was "radio" as far as anyone was concerned.

Then as tech improved they were able to shorten wavelengths down to where reasonable antenna lengths became possible, letting the public in on the action generally. They had to call the new frequencies something, and the 'standard' frequencies were actually extremely low, so they had nowhere to go but up. Thus we got high frequency (HF), very high frequency (VHF), ultra high frequency (UHF) and so forth.

So what was then considered high is now considered low, but no one ever bothered to change the terminology.

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@jeffypoooh Re: I for one take 2

Comment quality around these parts had taken a real dive...

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Re: I for one take 2

I will suggest you study radio propagation before buying any HF transceiver. It's like telling a 5-year-old you have bought him his very own motor vehicle. Comprehension of ALL aspects of radio propagation and the F1-F2-E-layer and D-layer should be studied and fully absorbed before opening the box. g6ypk QTHR and QRZ.com

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Re: I for one take 2

I wish contesting on HF could be banned. There is no need for this noise.

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Re: @jeffypoooh I for one take 2

A downvote? Seriously? Does context mean nothing to you people?

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Pint

Re: @jeffypoooh I for one take 2

GD "...a real dive..."

I see what you did there. Have an upvote.

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Pint

Re: @jeffypoooh I for one take 2

GD "...context mean nothing to you people?"

I appreciate your sense of humour.

MUF

Dive.

It cracked me right up.

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Pint

Certainly there's no intelligent life between 103 and 108 MHz

That's the top end of the FM Broadcast band. Not much signs of intelligent life there. LOL *

Above 108 MHz, you'll soon be into VHF Navigational Beacons and Aircraft pilots chattering away like magpies.

As already noted, "low frequency" is a defined frequency range, 30 to 300 kHz. One will find intelligent life within that band, specifically BBC Radio 4 'Longwave' on 198 kHz.

(* Acknowledge in advance that BBC 4 is also on 103.5-104.9 MHz. The joke is worth the discrepancy.)

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Trollface

Re: Certainly there's no intelligent life between 103 and 108 MHz

BBC Radio 4 is also available on long wave, at lower frequency, with more cricket. Some would argue that this increases the IQ of the station considerably...

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Pint

Re: Certainly there's no intelligent life between 103 and 108 MHz

Yes, 198 kHz. As was mentioned. :-)

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If those aliens are smart...

Those aliens have probably already looked at homo sapiens and decided they want ABSOLUTELY nothing to do with us! They'll keep really quiet!!

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Alien

Re: If those aliens are smart...

The aliens wrote us off after their own SETI effort picked up "Rick & Morty's Drivetime Top 40 Fantasy!! Brought to You by the Good People at Mattress Mart."

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Murchison Widefield Array

Is that the same guy with a Mote in his eye?

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What do they expect to find?

Some of the targets are billions of light years away. That means they’re looking for signals that are billions of years old. Than means they’re looking for a civilization that was transmitting billions of years ago. Which means that they’re looking for a civilization which is billions of years ahead of us.

Here’s the funny part. Suppose we’re even 100 years too early, before this civilization has developed the means to send a signal in the first place. Wouldn’t that be a bummer.

On the other hand, suppose they actually get a signal. What are the chances that they’re still around billions of years later, or still care?

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The hydrogen line is chosen because the radio noise is far lower at those frequencies, this, listening for ultra-weak signals become less problematic. Even to, on has to cryogenically perform front end miracles. "The Water Hole"? Never heard of this before, must be made up journalistic claptrap.

Nothing will be found. I emailed the extra terrestrials and asked them to keep quiet.

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Pint

"The Water Hole"? Never heard it, must be journalistic claptrap.

https://en.wikipedia.org/wiki/Water_hole_(radio)

Wiki says, "The term was coined by Bernard Oliver in 1971."

For what it's worth, I have heard of the term (in this context) innumerable times.

And I don't even pay all that much attention to SETI. 'Passing interest'

Cheers.

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low frequency radio waves?

Isn't 103 to 133MHz in the VHF band?

Just saying...

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Yup

Also worth mentioning, thunderstorms can emit very strange signals especially "EM bursts" linked to ball lightning.

Some folks on the amateur bands claim that "whistlers" are actually BL confined to a storm or the almost legendary "dark" variety which has not yet become visible.

These show up on IR scanners sometimes and have been linked to car alarms sounding just after (8-90 seconds) a storm as has been observed here not once but twice.

For more information see my research.

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