I saw the light

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KC8GTR, Nov 23, 2019.

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  1. KC8GTR

    KC8GTR Premium Subscriber QRZ Page

    Hello folks ,

    A newbie here so don't expect me to have read too many post and threads and such .
    So if this topic have been discussed , feel free to let me know .

    I do want to post a interesting question that takes the scope of VHF , UHF and beyond to the beyond limit .
    I'm curious about using light waves instead of RF waves .
    What efforts , projects and scientific papers have been created to explore using for example...LASER beams to communicate ?
    I can envision having a short focal length telescope spinning on top of my tower looking for a beam back at me .
    The same telescope could so easily be equipped with a simple LASER pointer at he eye piece ready to broadcast back to the other station .

    The hardware upstairs does not need to be too complicated , possibly be more affordable .
    Read on .
    I think it would be very similar to Yagi's , longer the boom and element count the narrower the beam pattern .
    So it's the same age old paradigm , gain versus beam width .
    That is also very true for light buckets , oops I meant telescopes .
    Short focal wave lengths telescopes have wider views but less resolving power .
    And the opposite is true , longer and more narrow view .
    It seems very possible to easily erect a " light bucket " contraption either a refactor , reflector or the very wide view ...the parabolic dish .
    If you can see the blinking red light on top of those commercial broadcasting towers , so would your light sensing device .

    Better yet...imagine bouncing your LASER beam off the moon !
    There are mirrors on the moon just for that purpose !
    Seriously folks...can you imagine making a EME voice QSO to and from the moon using 5mw at 650 nm !!!
    That would be outstanding .
    Consumer grade telescopes today comes with tracking hardware for following celestial objects , including the moon .
    High quality cameras are now common for the amateur astronomer but not sure if they are fast enough to catch a modulated LASER beam .

    What would it take for power ?
    I really don't know .
    I assume we are still required to keep visible LASER power to 5mw ?

    All this sounds really interesting and surely will challenge those who tries this mode out and see what performance , reliability and range they can achieve .
    I think with good results and favorable to the masses , this could be the beginning of high resolution voice , video , data ect ...bounced from the moon or across town .
  2. VE3CGA

    VE3CGA XML Subscriber QRZ Page

    My kids & I used a laser pointer to shine across a river valley here, using binoculars we could clearly see it reflecting off some signs about 1KM away
    Perhaps a rotating mirror at the top of a pipe mirror coated inside, could give 360 degree scanning
    I think the major fly in the ointment would be aircraft.
    Theres been several incidents reported of flights being hit by laser
    maybe they were on the ground, seems it would be hard to do when they are at cruising altitude
    You might have an angry F22 knocking at your door wondering why you targeted him:D:D
  3. KD0CAC

    KD0CAC Ham Member QRZ Page

    These guys do higher frequency play ,

    I read something on there mail-reflector the other day about this subject , and a new law about lasers being in the air / pointed up [ remember if your a couple of degrees up from parallel from the ground ] --- your pointed in the air ;(

  4. N1OOQ

    N1OOQ Ham Member QRZ Page

    Bouncing a laser off the Moon is non-trivial, more so than RF. This is done relatively routinely by astronomers for purposes of accurately measuring the Earth-Moon distance, to about a cm or two. They're actually bouncing off of the retroreflectors left there by the Apollo astronaunts, and there is one on an unmanned Russian lander.

    Anyway, they use relatively high power, beamed through a relatively large telescope, and basically count individual photons returning. Not that a determined amateur couldn't do it, but the resources needed are considerable. One wonders if FT8-type software would be useful?
  5. WR2E

    WR2E Ham Member QRZ Page

    Can a straight line ever be truly parallel to the ground?
  6. AA4PB

    AA4PB Ham Member QRZ Page

    Back around 1980 I was involved in using a UV laser to transmit a video signal between two tall buildings in NYC. While we did successfully get the signal between the two points, it wasn't reliable because the movement of the high rise buildings in the wind was more than the beam width of the laser.

    I took the laser on the commercial airliner with me. It was too delicate to allow it to be checked baggage and too big for carry on so I purchased it a ticket and strapped it into the seat beside me. Try explaining that to a stewardess :)
    KP4SX likes this.
  7. KD0CAC

    KD0CAC Ham Member QRZ Page

    I did not look at the details of the web sites discussion .
    But the impression I got was a blanket law about pointing , even very low power lasers in the air .
    I can only guess without checking further , that like ham radio [ to get some knowledge training / rules ] known and then with license we could use ?

    Kinda like drones , also have not played with , but is seems new laws come / and then go ?
    KY1K likes this.
  8. KF5LJW

    KF5LJW Ham Member QRZ Page

    You are kidding right? What do you think you are communicating on right now. Could it be Fiber Optic Transmission using Laser LED light to communicate at speeds up to 100 Gbs. perhaps? Sounds like that science paper is ancient history back in the 50's when Bell Labs started experimenting and using it in cooperation with Corning Glass.

    My senior project was a laser two-way data link using Laser LED penlight. My roommate made a laser microphone to shine on your neighbors window and listen in on what is going on inside. Today you can find hundreds of designs to do just that.

    Besides the dangers or shooting lasers over distance of land, lasers useful range is extremely limited. Basically used for short distances like LIDAR, range finding, and short distance networking. Is has a name: Free-space optical communication (FSO)
    Last edited: Nov 23, 2019
  9. AA4PB

    AA4PB Ham Member QRZ Page

    Probably any law against pointing lasers applies to those in the visible range.
  10. KF5LJW

    KF5LJW Ham Member QRZ Page

    No the most powerful lasers do not emit visible light. A low wattage Infrared or ultraviolet laser can blind you instantly and you will not see a thing. Just a terrible burning of the eyes and blindness. If you wanted to do damage and not get caught, use an invisible laser. No one will ever see where it came from or what happened.
    WG7X likes this.

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