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Need help with wireless video. (thanks)

Discussion in 'Electronic Basics' started by amer, Jul 12, 2003.

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  1. amer

    amer Guest

    Hello everyone.

    I need your advice for purchasing a small wireless video camera with a
    built-in transmitter. Main features I am looking for are :

    1- VERY high resolution, (comparable to modern Sony camcorders).
    2- Transmitter which can operate out of its "line-of-sight" also.
    3- Transmitter which can pass signal thru walls. (not mandatory)
    4- Moderately long range (e.g. 300 meters).
    5- Video to be recorded on a suitable device for later playback on TV.
    6- Long battery life (~6 hours)

    I have been browsing the internet but cant select the right model as I
    dont know much about electronics. Currently I have found one with '570
    lines of horizontal resolution'. Is this comparable to a normal
    camcorder? The website is :

    http://www.nctc.com/~dfluehe/

    What frequency, MHz or GHz, transmitter would be right for me? They
    start from 500 Mz and go upto 2.4 Ghz. Some, mentioned as for 'CCTV'
    equipment, go right upto 10 and 24 GHz also!

    How can I record the video for later playback on a normal home-TV?
    What type of
    device can I employ? Also what instrument would receive signal from
    the transmitter? Do I need to purchase an antenna or an amplifier
    also?

    Thanks very much for any help you can provide.

    Regards,
    Amer
     
  2. the Wiz

    the Wiz Guest

    Look for a receiver with S-Video output and a VCR with S-Video input. This has
    higher resolution than "standard" video.

    You need a transmitter-receiver pair that is compatible: same frequency, same
    modulation type, etc.

    The receiver will have a video output that can be connected to the video input
    of the VCR.

    For reliable long range communications, you may need a directional antenna at
    one or both ends. These will effectively limit the transmission to line of
    sight - you won't be able to move the transmitting or receiving antennas after
    they are aligned..

    The resolution of final image is limited by each piece in the path: camera,
    transmitter, receiver, VCR, video tape, display.

    If you're using a standard TV for display, you may not see much difference
    between cameras with different resolutions. If you're using a "monitor" quality
    display, you will be able to see the difference, assuming the resolution isn't
    lost in the RF chain.



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  3. DarkMatter

    DarkMatter Guest

    snipped fairly good application analysis...

    Not cheap.

    It wouldn't be worth its salt if it couldn't in your 300 meter
    realm. You want the low frequency stuff for that, not the GHz stuff.

    It's out there, believe me.

    You want that in stereo? How about a data comm link as well?

    That's you end. You do what you want with it after you get it.

    Actually, that is your end as well. Battery belts aren't cheap, but
    are available. The battery packs that are offered bellow seem quite
    sufficient as well, however.

    snipped link

    Fly by night lameness. Lo res at best.

    The product you want is probably WAY outside your ability to afford
    it. The units you describe are not little PC cam playtoys from the
    computer store, they are professional grade equipment.

    You sound as if you think the size of the box equates with price.
    It does not. The level of quality you are demanding is nowhere near
    normal PC techy consumer level crap... Just so you know.

    The degree of "resolution" you are pining for will cost you, if you
    ever get it at all. If you are serious, you can get it all...

    www.avalonrf.com

    It does get any better than that place. Custom solutions are
    available. Cop cars got 'em. Custom roof mount central unit, 4 cam
    capability... 9" flip down monitor...
     
  4. DarkMatter

    DarkMatter Guest

    That should be "doesn't". Damned spell checkers.
     
  5. amer

    amer Guest

    Dear Friend.

    Thanks a lot for the helpful information.

    I have inspected my VCR and it has an Audio-Video (A/V) IN and A/V
    OUT. It also has an RF IN and RF OUT. Is S-video different from these
    two? What is the Standard video?

    Also, transmitters come in many ranges from 500 Mhz upto 2.4 GHz and
    also 10 and 24 GHz for FMTV. Can you advise which one I should buy?

    I cannot install visible directional antennas on my transmitter or
    reciever, especially my transmitter because I would be wearing the
    camera on my body and I may change position at times. For a range of
    300 meters, can I do away with my transmitter antenna? Moreover, for
    penetration thru walls and out of line-of-sight, do I have have to use
    a higher frequency transmitter?

    I have a Sony Trinitron TV. I also have a 17" monitor with my computer
    which has a TV Card. The camera I am considering has 570 lines of
    horizontal resolution. Speaking in layman (me) terms, can I expect the
    video quality of the programs and movies we generally watch on TV in
    our daily lives?

    Thanks again for the help.
    Best Regards,

    Amer
     
  6. the Wiz

    the Wiz Guest

    S-Video is a different connector - more like the PC keyboard and mouse
    connectors. You will use the standard video connectors because they are all you
    have.
    Get a transmitter/receiver combination that offers the range you need. Be aware
    that the advertised range is typically for unobstructed line of sight. The
    range under "real world" conditions will be less. Consider the advertised range
    on wireless PC networking (wi-fi, 802.11 at 2.4GHz). It's something like 300
    meters outdoors, 50 meters indoors. In the real world, it's also dependent on
    the antennas used and any sources of interference. With the wireless baby
    monitor on at our house, a laptop wireless card can't sync with the router from
    8 meters away on the same floor. A friend has a three level house with the
    wireless router in the basement and desktop PC's with wireless network cards
    (which have external antennas) on each the other floors. The maximum distance
    is about 20 meters and the PC's work OK.
    No. Note that your are at the distant end of the range of most non-licensed
    transmitters.
    Frequency is not a major issue. Unlicensed transmitters are power limited based
    on the frequency used and most will provide similar range whether 2.4GHz or
    10GHz.

    Assuming that the transmitter you choose has provisions for an external antenna
    (not all do) you may be able to increase the range. Get a metal hat
    (construction hard hat) and mount a vertical antenna (non-directional, but
    definitely visible) on it to get the antenna above most of the obstructions and
    provide a ground plane for the antenna. To further increase the range, get a
    relatively wide beamwidth antenna for the receiver (for 2.4GHz, something like
    the Mini-Tenna at http://www.etherdesigns.com/pages/3/index.htm). Point the
    receiving antenna at the area to be covered and check the coverage by walking
    around with your camera/transmitter to determine the best aiming of the receiver
    antenna.

    If the above doesn't give you enough range, you may be looking for a more
    powerful (licensed) transmitter. Depending on your country, there may or may
    not be reasonably priced commercial equipment available. If your application is
    personal (non-commercial), you might consider getting an amateur radio license -
    hams can run much more powerful transmitters. Remember that there are penalties
    for a higher power transmitter - it costs more, weighs more, and needs bigger
    (and heavier) batteries.

    Antennas are a visible solution to increasing range, but they require no power
    and add very little weight, compared to a more powerful transmitter and it's
    associated batteries.

    Consider the relative range of 2.4GHz wi-fi in different settings:
    http://www.weca.net/OpenSection/range.asp?TID=2

    I'm using wireless networking as a reference because both wi-fi and video are
    high speed, wide band signals and there is published information about wi-fi.
    Your should have adequate resolution. However, be sure that you can return the
    camera and the transmitter/receiver for refund if they don't perform as
    advertised.
    Your application sounds like a convention floor interview project (or a school
    reunion), with the wearable camera and 6 hour battery requirements. In a
    situation like this, the ideal placement for the receiver would be the top
    center of the area, with cable to the VCR and TV.

    *** You can't put the camera in your shirt pocket and the transmitter in your
    trouser pocket and get 300 meters range.***
    You might get 10 meters if you're turned so the transmitter antenna is exactly
    aligned with the receiver antenna, but you may only get 3 meters.

    The criteria for distance when using RF are antenna height, antenna gain, and
    transmitter power. There are no shortcuts and no easy answers.


    More about me: http://thelabwiz.home.mindspring.com/
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    Drivers for Pablo graphics tablet and JamCam cameras: http://home.earthlink.net/~mwbt/
    johnecarter atat mindspring dotdot com. Fix the obvious to reply by email.
     
  7. amer

    amer Guest

    Hello Wiz.

    It was really great to receive a detailed and enlightening response
    from you, and just in time..I had almost made up my mind to order.
    Sorry for my late posting; I could not login properly to the internet
    since few days.

    You have given some really great tips on increasing my range through
    antennas etc. while remaining within the realm of the unlicensed
    transmitters. And also all the pros and cons of going wireless for
    video. Thanks again.

    However, what I gather from your advice is that wireless video is
    practically useless unless both sources are stationary with properly
    aligned high rise antennas. Or else, licensed transmitters are the
    only solution. Thus I am now seriously considering my options with
    licensed transmitters.

    You mention Unlicensed transmitters are power limited; how about using
    a high power amplifier with my transmitter? Will that give me a large
    out of line of sight range without antennas? If amps can do the job, I
    hope they are not too large or costly for me. Whats your advice?

    Are licesed transmitters the ones that are advertized as to work with
    the FMTV? Also, with these, can I expect an out of line of sight range
    of 300 meters (thru walls also)?

    Finally, some points I could not comprehend in your post. Pls.
    elaborate.
    Is a radio license issued to radio stations only? Sorry dont know much
    about them.
    What are hams?
    That probably means it is not portable at all. What is generally its
    size? Roughly, can I expect anything the size of a CDROM drive?

    Thanks a lot for your help.

    Amer

    (p.s. your guess of the supposed method of use for this camera is
    correct. However, the purpose is a different. Its more of an
    investigative nature.)
     
  8. the Wiz

    the Wiz Guest

    You've probably seen the wireless cameras that are used by TV news crews. These
    typically use a licensed transmitter with higher power. You should also notice
    that the camera and battery pack (either on-camera or on a battery belt) have a
    combined weight of 10 kilos or more. Part of this is the more capable camera
    (better optics, wide range zoom lens, etc) but a portion of it is battery
    weight.
    The unlicensed transmitter is unlicensed because it is power-limited. Adding an
    amplifier will move it out of the unlicensed power category. Depending on your
    country, you could:
    never be noticed
    receive a warning
    be fined
    receive jail time
    Licensed video transmitters typically operate on assigned frequency bands and
    require a matching receiver. They are not in the standard TV band.
    Most countries issue amateur radio operator (ham) licenses to people who pass a
    test on radio theory, law, and some level of receiving/sending Morse code.
    Depending on the country and the frequencies used, hams can use amplifiers for
    up to 1000 wats of power - obviously not portable or battery powered ;-)
    However, an amateur transmitter that delivers a few watts is many times more
    powerful than the unlicensed transmitters that deliver on a few milliwatts
    (think in terms of meters versus millimeters for a relative value comparison).
    More about me: http://thelabwiz.home.mindspring.com/
    VB3 source code: http://thelabwiz.home.mindspring.com/vbsource.html
    VB6 source code: http://thelabwiz.home.mindspring.com/vb6source.html
    VB6 - MySQL how to: http://thelabwiz.home.mindspring.com/mysql.html
    Drivers for Pablo graphics tablet and JamCam cameras: http://home.earthlink.net/~mwbt/
    johnecarter atat mindspring dotdot com. Fix the obvious to reply by email.
     
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