Joined: 30 Jul 15
Monday May 9 2016, 6:00 PM GMT +8
My PC runs 24/7 & I use the SETI Screen Saver. It's attractive, meaningful, and always draws the attention of visitors.
I have a few questions and I would like anyone to answer them for me? Your answers will help in my understanding of the information being displayed.
I've seen signals described in 5 different ways. Here are typical examples:
#1 Best Triplett: power XXX
#2 Gaussian: power XXX
#3 Best Gaussian: power XXX
#4 Pulse: power XXX
#5 Best Pulse: power XXX
Why are there 5 different types of received signal power? What does each one mean, in plain English?
The "XXX" I use in the above examples are simple positive numbers. Examples could be 0.4, 1.2, 3.1, etc. These are all positive numbers. I assume that, using the above examples, 3.1 is a signal power and is stronger than a signal power of 0.4? What are the signal power UNITS that are omitted?
In "earth-based" communications, transmitter signal power may cover a range of milliwatts, watts, kilowatts, etc. using devices like cell phones, walkie-talkies, 2-way radios, and on up to radio or TV broadcast transmitters.
Again, in "earth-based" communications, received signal power is typically described in terms of "dBm," i.e., decibels referenced to one milliwatt of power. Thus, 0 dBm = 1 mw, +30 dBm = 1 watt, -3 dBm = 0.5 mw, etc.
All earth-based communications requires the received signal to be above the thermal noise floor, -175 dBM/Hz, in order to be "seen." However, intelligent signals from far out in the cosmos, to be seen, will not be this strong. To be detected at all they must be of a repetitive nature, i.e., a repeating digital string, or some such, and detected by signal integration. I've known this to work for low-level signals from 20 to as much as 30 dB below the thermal floor.
What 'power measurement' units are used by SETI for these very low-level received signals? What are their measurement units? Why are they all positive in the SETI Screen Saver display?
River Song (aka Linda Latte on planet Earth)
"Happy I-Phone girl on the GO GO GO"
©2018 University of California
SETI@home and Astropulse are funded by grants from the National Science Foundation, NASA, and donations from SETI@home volunteers. AstroPulse is funded in part by the NSF through grant AST-0307956.