by alter-ego » Sun Dec 08, 2013 8:51 am
neufer wrote:alter-ego wrote:
Art - Are you using 10.5cm wavelength / 2.86GHz?
I assume you're calculating antenna diffraction ≈ λ/Diameter (the Half-Power Beam Width)?
Yes to all that.
I get a beam an order of magnitude wider than Chris's laser beam
but with a power 3 orders of magnitude stronger so the beam intensity is ~10 times stronger.
I extrapolated from Chris's photon count based upon photons that are 200,000,000 times weaker
when they should have been 200,000 times weaker
so I really should have gotten 0.4 microwave photons per second. What do you get?
First off, I haven't ignored your question. Between the holidays and unfortunate timing of forum access problems, I haven't responded.
Well, care is needed to keep track of the details which mostly amounts to orders of magnitude here. If I did my calculations correctly, your and Chris' final photon collection rates per m
2 are off by orders of magnitude. This was significant enough that I wanted to review my calculations first. So to try to keep things clearer, I'm posting calculation details below that you and Chris can review if you wish.
OK, cutting to the chase, I get the radio telescope photon collection time per m
2 ~66 hours at a distance of 10,000 ly, and a laser photon collection time ~382,000 yrs. To validate this, I first wanted to first calculate the photon collection ratio using the ratio approach as you did above. I believe the cyan-highlighted equation below (incorporating the constants) correctly predicts the laser-to radio photon collection time to be ~50,000,000. This ratio approach above yields the same answer as the ratio of specific cases calculated below.
The case-specific photon collection time calculations are:
These are simplified calculation that don't attempt to account for the next issue of interstellar extinction which attenuates the photon counts. I've also looked at this but no need to go there here.
[quote="neufer"][quote="alter-ego"]
[i]Art[/i] - Are you using 10.5cm wavelength / 2.86GHz?
I assume you're calculating antenna diffraction ≈ λ/Diameter (the Half-Power Beam Width)? [/quote]
Yes to all that.
I get a beam an order of magnitude wider than Chris's laser beam
but with a power 3 orders of magnitude stronger so the beam intensity is ~10 times stronger.
I extrapolated from Chris's photon count based upon photons that are 200,000,000 times weaker
[b][color=#FF0000]when they should have been 200,000 times weaker[/color][/b] :!:
[u]so I really should have gotten 0.4 microwave photons per second[/u]. What do you get?[/quote]
First off, I haven't ignored your question. Between the holidays and unfortunate timing of forum access problems, I haven't responded.
Well, care is needed to keep track of the details which mostly amounts to orders of magnitude here. If I did my calculations correctly, your and Chris' final photon collection rates per m[sup]2[/sup] are off by orders of magnitude. This was significant enough that I wanted to review my calculations first. So to try to keep things clearer, I'm posting calculation details below that you and Chris can review if you wish.
OK, cutting to the chase, I get the radio telescope photon collection time per m[sup]2[/sup] ~66 hours at a distance of 10,000 ly, and a laser photon collection time ~382,000 yrs. To validate this, I first wanted to first calculate the photon collection ratio using the ratio approach as you did above. I believe the cyan-highlighted equation below (incorporating the constants) correctly predicts the laser-to radio photon collection time to be ~50,000,000. This ratio approach above yields the same answer as the ratio of specific cases calculated below.
[img2]https://lh4.googleusercontent.com/-Fg1bLnSDOtI/UqFe6csVNOI/AAAAAAAACTQ/kSnn3HB0hGU/s976/Ratio%2520Calculation%2520Equation.JPG?gl=US[/img2]
The case-specific photon collection time calculations are:
[img2]https://lh5.googleusercontent.com/-t0OrLWsHsBI/Up7PdmEY2hI/AAAAAAAACRc/X3FB4H9h-Eg/s800/RT-70%2520Radio%2520Telescope.JPG[/img2]
[img2]https://lh4.googleusercontent.com/-75Jbjy2uQBo/Up7ZbzOGN8I/AAAAAAAACRk/ClAGNmhJPdQ/s1060/100%2520Watt%2520Laser.JPG[/img2]
These are simplified calculation that don't attempt to account for the next issue of interstellar extinction which attenuates the photon counts. I've also looked at this but no need to go there here.