Posts by Dave

1) Message boards : SETI@home Science : How are alphanumeric designations generated for candidate signals? (Message 1756796)
Posted 16 Jan 2016 by Profile Dave
Post:
Can anyone tell me how designations are generated for candidate signals? I think I have some of it figured out, but maybe someone can help fill in the blanks. Using SHGb02+14a, it seems like this means:

SH - SETI@Home
Gb - Gaussian (barycentric)?
02 - Right ascension
+14 - Declination
a - First detection from this location?

Thanks all,

Dave
2) Message boards : SETI@home Science : Question about signal polarization (Message 1636870)
Posted 3 Feb 2015 by Profile Dave
Post:
But I would assume that a natural signal would be more likely to be un-polarized than an intentional signal, not to say that an intentional one would be polarized. I wonder if there are even natural sources of polarized radio signals - I would guess that some phenomenon could possibly do that, maybe nature's unlikely version of a million monkeys typing randomly for a million years managing to output a Shakespearean play by chance. ; )
3) Message boards : SETI@home Science : Question about signal polarization (Message 1636825)
Posted 3 Feb 2015 by Profile Dave
Post:
It sounds like polarization, in the long run, isn't a very useful characteristic for radio astronomers.

In semi-related news, nice that Kepler - K2 - is in service again!
4) Message boards : SETI@home Science : Question about signal polarization (Message 1634391)
Posted 29 Jan 2015 by Profile Dave
Post:
Hi Gary,

Thanks for the quick answer! That's exactly the information I needed. I'm working on a story and want it to be accurate, so this helped a lot.

Dave
5) Message boards : SETI@home Science : Question about signal polarization (Message 1634312)
Posted 28 Jan 2015 by Profile Dave
Post:
Hello everyone,

I have a few questions about signal polarization as it applies to SETI research in particular, although I suppose it's really more of a basic radio question. I tried a search here but got lots of returns and couldn't effectively sort through them.

Anyway, let's assume:

...an intentional ETI signal is discovered, and the polarization periodically flip-flops. (As I understand it, at the long distances dealt with, detecting polarization might be a bit tricky, but for this let's say it's easy to detect.)

...the science team isn't concerned about the signal polarity and therefore isn't checking it. To them, the signal is just one of undetermined and unexamined polarity.

...another science team looks at the signal but they're experiencing some sort of technical glitch and can only detect the signal when the polarity is the one they're currently able to see.

So the questions:

What sort of glitch, if any, would let them detect only one of the two polarities? What equipment would be the source of the problem?

Is this even a scenario that makes any sense in the real world, or is it something that wouldn't/couldn't happen because of the nature of radio signals?

Just so you know, I'm getting in way over my head. I usually can't even find the TV remote. ; )

Dave
6) Message boards : SETI@home Science : For mathematicians or anyone that wants to take a look... (Message 1539825)
Posted 11 Jul 2014 by Profile Dave
Post:
No complaints from me, I'd rather see her reputation for friendliness be acknowledged. ; )
7) Message boards : SETI@home Science : Chirping/de-chirping question (Message 1517958)
Posted 18 May 2014 by Profile Dave
Post:
Believe it or not, I actually understand that. ; )

I'm constantly amazed at the precision and sensitivity of these pieces of equipment.
8) Message boards : SETI@home Science : Chirping/de-chirping question (Message 1517893)
Posted 18 May 2014 by Profile Dave
Post:
Hello everyone,

First, thank you to everyone for your patience with my questions. I have a new one - I tried searching the various threads here and didn't find anything that I think answered my question, so I'll pose it here.

During the de-chirping process, it sounds as if there are many, many different possible results, each with a different amount of Doppler shift. Is the goal of this process to find the one that results in (near) zero shift?

So for example, let's say the search frequency is 1420 MHz. The science team is receiving signals with Doppler, whose barycentric frequency (See? I'm getting just enough knowledge to be dangerous.) is 1420 MHz. It sounds like the goal of de-chirping is to see how much Doppler shift the signal is undergoing. If that's correct, what can be gained from having that information? Obviously the scientists would know where the antenna is pointing, and motion over time would, I'm guessing, tell us about how far out the signal is coming from.

Or am I completely lost? Thank you in advance.

Dave
9) Message boards : SETI@home Science : For mathematicians or anyone that wants to take a look... (Message 1516999)
Posted 16 May 2014 by Profile Dave
Post:
Ah, but for the most post music IS mathematical. Not sure about the work of John Cage and similar composers.
10) Message boards : SETI@home Science : For mathematicians or anyone that wants to take a look... (Message 1516813)
Posted 16 May 2014 by Profile Dave
Post:
I wish that either I'd had the presence of mind to become interested in math as a kid (or I wish I'd had motivating teachers, but that's just shifting the blame).
11) Message boards : SETI@home Science : For mathematicians or anyone that wants to take a look... (Message 1511053)
Posted 2 May 2014 by Profile Dave
Post:
Yeah, it is! So many amazing... I hate to say coincidences, but interesting patterns and oddities.
12) Message boards : SETI@home Science : For mathematicians or anyone that wants to take a look... (Message 1511020)
Posted 1 May 2014 by Profile Dave
Post:
It's ironic how interesting math is for me now that I have a "reason" for it to be so, even math without a practical application. My teachers in school weren't very motivating - the math was all taught by rote, with none of the mysterious joy that really exists.
13) Message boards : SETI@home Science : For mathematicians or anyone that wants to take a look... (Message 1510899)
Posted 1 May 2014 by Profile Dave
Post:
Thanks Bob! I'm zeroing in on how I would send a signal if I were basking on some exoplanet...

Dave
14) Message boards : SETI@home Science : For mathematicians or anyone that wants to take a look... (Message 1510865)
Posted 1 May 2014 by Profile Dave
Post:
Hi Chris,

I have a quick question for you - is there a benefit of using FSK instead of Amplitude SK for long distance transmissions?

Dave
15) Message boards : SETI@home Science : For mathematicians or anyone that wants to take a look... (Message 1510793)
Posted 1 May 2014 by Profile Dave
Post:
Actually, I've done both. I'm hoping to take that basic idea but make it more realistic. Overall I liked them, each in different ways, but I felt the "eccentric rich guy goes to space" was a bit too much... too Hollywood-y. ; ) There'd be no futuristic machine in mine, no attempt to travel any further than halfway around the world. As much as practical, I want to show what it would really be like.
16) Message boards : SETI@home Science : For mathematicians or anyone that wants to take a look... (Message 1510712)
Posted 1 May 2014 by Profile Dave
Post:
Part two. I did a real Amazon search, rather than one through Google, and found the book, as well as a couple of others that might be good - "The Mysterious Signals From Outer Space" and "Interstellar Contact." He's quite a prolific writer, some in science fiction, but if he's taken a serious look at the subject in these other books the information could be useful. Thanks for the tip!

Dave
17) Message boards : SETI@home Science : For mathematicians or anyone that wants to take a look... (Message 1510711)
Posted 1 May 2014 by Profile Dave
Post:
Hi Chris,

Thanks for the reply! I looked online for the book and found a copy at Amazon, but there's zero information - no author, no summary, no publisher - so I'm not absolutely sure if it's the same book, despite the title. However, Duncan Lunan has a website of his own (http://www.duncanlunan.com/), and although he doesn't sell the book there, there's some information that might be helpful (I'll still poke around online to find a copy). He also has an article published there that might be of interest, "Epsilon Bootis Revisited" (http://www.duncanlunan.com/epsilonbootis.asp).

Dave
18) Message boards : SETI@home Science : For mathematicians or anyone that wants to take a look... (Message 1510710)
Posted 1 May 2014 by Profile Dave
Post:
Thanks Rob! I found a decent overview of FSC at Wikipedia, "the source for all things mostly accurate." ; ) It looks like FSC might be exactly what I'm looking for.

Dave
19) Message boards : SETI@home Science : For mathematicians or anyone that wants to take a look... (Message 1510564)
Posted 1 May 2014 by Profile Dave
Post:
Thanks William! I read up a bit on Lyman lines (until I got tangled in a bunch of Greek letters!), so I have a very basic understanding of them, but I don't know why such a frequency (times whatever) would be better than 1420 MHz.

What would the benefits of a modulated carrier be over one that's CW? (Less stress on the transmitter?)

Dave
20) Message boards : SETI@home Science : For mathematicians or anyone that wants to take a look... (Message 1510499)
Posted 30 Apr 2014 by Profile Dave
Post:
Hi Rob,

Thanks for the suggestions!

So maybe instead of polarization I should use two different frequencies? I was originally thinking about hydrogen and hydroxyl, but I thought that they're far enough apart that someone searching for a signal might not pick up on both. Or possibly hopping from a few Hz below 1420 for zeroes and a few Hz above 1420 for ones?

As for the duration of each pulse or null, I was thinking somewhere around 10 seconds (obviously not exactly 10 - ET wouldn't know what a second is), with maybe a three second integration time (which seems to be somewhat common for at least some programs). By keeping the pulses and nulls relatively short, I was thinking that there would be enough time for a repeat of the signal that it would be apparent a null stretch wouldn't be signal loss.

Going back to the hopping above and below 1420 - maybe a string of "zero" pulses and nulls a little below 1420, a string of "one" pulses above 1420, and a continuous beacon right at 1420. I know that power requirements make a continuous beacon problematic, but I'm hoping my ETs have found a way to get around that. ; )

Dave

PS: I've been running SETI@home off and on for the last few years, and continuously now on a dedicated Linux laptop for the last few months. I'm sure I'm way down the list in work completed, but it's still fun to be involved.

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