#301020 - 01/08/2007 14:33
Re: Long Distance wireless link
[Re: JBjorgen]
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carpal tunnel
Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
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You might want to have someone independently check my math.
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Bitt Faulk
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#301021 - 01/08/2007 14:41
Re: Long Distance wireless link
[Re: JBjorgen]
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pooh-bah
Registered: 13/01/2002
Posts: 1649
Loc: Louisiana, USA
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You may wish to consult this site. They have a calculator on there as well as some precalculated distances. Stu
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If you want it to break, buy Sony!
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#301022 - 01/08/2007 17:24
Re: Long Distance wireless link
[Re: JBjorgen]
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carpal tunnel
Registered: 29/08/2000
Posts: 14496
Loc: Canada
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Quote:
I'll be lucky if I can get 25' on the apartment building side., so that means it'd need to be about 150' on the other side. Hmm...that may be cost prohibitive. We've got a building that's about 40' high and I was hoping to be able to just put a mast on top of it.
Note that since your hop is across salt water, Bitt's calculation suggests 83' above sea level (at high tide). Odds are very good that your apartment is already higher than this, though the beachfront spot likely is not.
cheers
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#301024 - 01/08/2007 18:49
Re: Long Distance wireless link
[Re: JBjorgen]
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carpal tunnel
Registered: 10/06/1999
Posts: 5916
Loc: Wivenhoe, Essex, UK
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Quote:
I wonder how high that rocky island in the middle is, and who owns it. Hmm....
Dunno, but it doesn't look like a good place for shipping:
http://tinyurl.com/yr9p9v
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Remind me to change my signature to something more interesting someday
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#301025 - 01/08/2007 19:08
Re: Long Distance wireless link
[Re: andy]
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carpal tunnel
Registered: 13/07/2000
Posts: 4180
Loc: Cambridge, England
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Oh, that's where Belize is. Now I'm thinking that the relevant maths is: 83-foot mast, plus Gulf of Mexico hurricane season, equals severe packet loss  Peter
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#301029 - 08/08/2007 15:14
Re: Long Distance wireless link
[Re: maczrool]
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carpal tunnel
Registered: 24/12/2001
Posts: 5528
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Quote:
Quote:
No. Seriously. A DVD burner's diode laser can operate at 200mw?
See here. I've tried it. It really does work.
Not quite as much destruction but you can get a violet laser diode out of a PS3 optical assembly. I got the donor parts off eBay for £40 exc shipping and it works pretty well. Probably not the safest thing to leave lying around tho. Must get some of the don't look into the laser beam with your remaining eye stickers made I think...
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#301030 - 08/08/2007 20:53
Re: Long Distance wireless link
[Re: tman]
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old hand
Registered: 20/07/1999
Posts: 1102
Loc: UK
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This thread inspired me, and I remembered I had a duff DVD-rw drive in the loft I had kept for exactly that purpose. So over the weekend I pulled it apart and scavenged the diode. With a little work, and the optics from a cheap (and non-functional) laser pointer, I produced the MEGApointer MK1   It's not quite finished yet, I still need to recess the screws and polish it! It's got a little PSU module inside that's designed for running CPU core voltages, set to 3.5V, and runs from 3 AAA cells in a holder I scavenged from an old LED head-torch. About 32mm in diameter and perhaps 100mm long. The laser optics are adjustable. Set to produce a parallel beam it gives a spot size of about 3mm, which still has enough energy to shrink heatshrink tubing! Focussed to a minimum spot size at perhaps a foot, the beam is only around 0.2mm across, and melts plastic so fast you can write your name with it. Wave it around on the antistatic mat it's on in the picture and it leaves a trail of smoke behind The beam diverges quickly after the focus point, and at 15 feet its about 3 inches across. I'd estimate the output power is at least 150mW. It's probably capable of more. Quite fun for a quick and dirty afternoons work. pca
Edited by pca (08/08/2007 21:07)
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#301031 - 08/08/2007 20:56
Re: Long Distance wireless link
[Re: pca]
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carpal tunnel
Registered: 24/12/2001
Posts: 5528
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Quote:
This thread inspired me, and I remembered I had a duff DVD-rw drive in the loft I had kept for exactly that purpose. So over the weekend I pulled it apart and scavenged the diode. With a little work, and the optics from a cheap (and non-functional) laser pointer, I produced the MEGApointer MK1
Cool! Tried burning anything with it yet? 
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#301033 - 08/08/2007 22:44
Re: Long Distance wireless link
[Re: tfabris]
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member
Registered: 06/04/2000
Posts: 158
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So that's what all the recent news stories about sharks being seen off the SW England coast were - secret pca prototypes...
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#301034 - 09/08/2007 00:13
Re: Long Distance wireless link
[Re: MarkH]
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carpal tunnel
Registered: 29/08/2000
Posts: 14496
Loc: Canada
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Quote:
So that's what all the recent news stories about sharks being seen off the SW England coast were - secret pca prototypes...
Ooooo...sharks with frickin' laser beams attached to their heads!
From PCA, of course!
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#301035 - 09/08/2007 15:45
Re: Long Distance wireless link
[Re: pca]
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carpal tunnel
Registered: 20/12/1999
Posts: 31602
Loc: Seattle, WA
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May I just say, looking at your picture and reading your description, it's really only a short step away from a true ray gun. That shiny metal casing is just dying to have a pistol grip handle attached to it. Or even better, you could mount it inside one of these. On the other hand, you already said that it has a limited focal point, so what it truly needs is a proper collimating lens. You could mount the collimating lens on a sort of extension, making it truly look like a ray gun, such as this or especially this. *drool*
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#301036 - 10/08/2007 01:18
Re: Long Distance wireless link
[Re: JBjorgen]
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member
Registered: 06/04/2000
Posts: 158
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Would something like this mesh network work for you ? http://meraki.com/products/solar/Might be something which would provide extra services to the local community too. Regards Mark
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#301037 - 10/08/2007 01:47
Re: Long Distance wireless link
[Re: MarkH]
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carpal tunnel
Registered: 19/01/2002
Posts: 3584
Loc: Columbus, OH
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That looks like it'd be a fantastic product to mount to the antennas. I was going to have to find something that would be weatherproof and powered by solar anyway. I'm waiting until my contacts that are there in Belize return to the location in Sept. to find out if there is any of the higher ground nearby that it would be conceivable for me to use as a midpoint to avoid having a 150 ft. tower. The closest hill or mountain is still several miles away and further inland, and then there's the problem of finding out who owns it and getting permission to put an antenna there. Prospects not looking so good at the moment 
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~ John
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#301038 - 10/08/2007 14:44
Re: Long Distance wireless link
[Re: maczrool]
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carpal tunnel
Registered: 08/03/2000
Posts: 12344
Loc: Sterling, VA
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Wasn't sure if anyone had run across this yet. It also showed up here.
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Matt
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#301039 - 10/08/2007 15:20
Re: Long Distance wireless link
[Re: Dignan]
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old hand
Registered: 14/04/2002
Posts: 1172
Loc: Hants, UK
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Yeah, I spotted that on the same day as reading Patrick's post - amazing coincidence!
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#301040 - 13/08/2007 09:05
Re: Long Distance wireless link
[Re: tfabris]
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old hand
Registered: 20/07/1999
Posts: 1102
Loc: UK
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It's already got a collimating lens, but I tweaked it to come to a point at a foot or so. It can be untweaked, and gives a nice parallel beam thats quite impressive in the dark. One problem is that at 650nm the human eye isn't all that sensitive, so the beam doesn't look as powerful as it really is. It hits peak brightness quite early on, and more power doesn't appear visibly brighter. The impressive bit is when you expand the beam out to about 6 inches across and it's STILL much brighter than an ordinary laser pointer It makes a damn impressive red flashlight if you widen the beam enough! A spot six feet across on trees two hundred feet way is easily bright enough to make out all the details. After this success, I bought another 10 surplus DVD writers at a radio rally yesterday for £15. Now I just need to figure out the best method of combining all the outputs into one beam pca
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Experience is what you get just after it would have helped...
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#301041 - 13/08/2007 10:49
Re: Long Distance wireless link
[Re: pca]
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veteran
Registered: 21/03/2002
Posts: 1424
Loc: MA but Irish born
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#301042 - 13/08/2007 15:06
Re: Long Distance wireless link
[Re: pca]
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carpal tunnel
Registered: 20/12/1999
Posts: 31602
Loc: Seattle, WA
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Quote:
Now I just need to figure out the best method of combining all the outputs into one beam
See? See? Told you so.
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#301043 - 13/08/2007 15:09
Re: Long Distance wireless link
[Re: pca]
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carpal tunnel
Registered: 20/12/1999
Posts: 31602
Loc: Seattle, WA
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Quote:
It's already got a collimating lens, but I tweaked it to come to a point at a foot or so
So, from someone who doesn't know much about lasers or optics, is it possible to make a lens assembly that focuses the beam at a point like you did, only have that point be the entire length of the beam (a true parallel beam)?
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#301044 - 13/08/2007 15:38
Re: Long Distance wireless link
[Re: pca]
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carpal tunnel
Registered: 13/02/2002
Posts: 3212
Loc: Portland, OR
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Quote:
Now I just need to figure out the best method of combining all the outputs into one beam
And, once you're done that, see if you can get a red laser, a green laser, and a blue laser to focus in one spot, so you can build a laser-TV from it...
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#301045 - 13/08/2007 15:41
Re: Long Distance wireless link
[Re: tfabris]
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old hand
Registered: 20/07/1999
Posts: 1102
Loc: UK
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Um. Given a perfect lens and a perfect vacuum in the complete absence of gravity or magnetic fields, I think it's possible. A little fiddly, in other words pca
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Experience is what you get just after it would have helped...
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#301046 - 13/08/2007 16:27
Re: Long Distance wireless link
[Re: pca]
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carpal tunnel
Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
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Quote:
Now I just need to figure out the best method of combining all the outputs into one beam
"Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light."
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Bitt Faulk
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#301047 - 15/08/2007 01:25
Re: Long Distance wireless link
[Re: tfabris]
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carpal tunnel
Registered: 17/12/2000
Posts: 2665
Loc: Manteca, California
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Quote:
Quote:
It's already got a collimating lens, but I tweaked it to come to a point at a foot or so
So, from someone who doesn't know much about lasers or optics, is it possible to make a lens assembly that focuses the beam at a point like you did, only have that point be the entire length of the beam (a true parallel beam)?
You use the multiple laser diodes to pump another gain medium causing it to laze.
http://www.llnl.gov/nif/psa/sshcl.html
Edited by gbeer (15/08/2007 01:40)
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Glenn
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#301048 - 21/08/2007 08:11
Re: Long Distance wireless link
[Re: JBjorgen]
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carpal tunnel
Registered: 13/07/2000
Posts: 4180
Loc: Cambridge, England
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Quote:
[Belize] Both locations are within 10 ft of sea-level.
Yow. I guess as of today they're still within 10ft of sea-level, but below, not above? Hope you (and/or your colleagues, if you're not out there yet) are OK. Looks like they might be needing more charity work than you thought...
Peter
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#301049 - 21/08/2007 13:23
Re: Long Distance wireless link
[Re: pca]
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veteran
Registered: 21/01/2002
Posts: 1380
Loc: Erie, CO
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Can you mount the laser in a plane, hack into the system and change the coordinates for the test firing and cook up a monster batch of popcorn in your professor's house? If so, I will be the Kent to your Knight.
"I want to see more of you in the lab"
"Ok, I'll gain weight"
Obscure?
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