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Video Transmitter/Receiver question - radio license question

Hello, I am installing a video security system at the business where I work. The cameras are mounted in enclosures recessed into the ceiling. I have minimal access to the video output cable on the camera when the camera is mounted in the enclosure.

This makes it sort of difficult to position the camera, set the zoom, and adjust the focus--I can't connect a local video monitor to allow me to see what the camera is actually viewing. In order to solve this problem, I have decided to buy a video transmitter and connect this to the output of my video switcher in the electronics room (quite a distance from the many cameras). I would then mount the transmitter out in the main building amid the cameras. I would then carry a receiver and portable video monitor to use for camera adjustments. I wouldn't use it very much--maybe a few hours every few months. There are walls inside the building that the signal would need to penetrate plus it would need to penetrate the roof for adjustment of outdoor parking lot cameras.

The question I have relates to the video transmitter/receiver link: I have found on eBay, and Froogle transmitter/receiver pairs that appear to be made in China. I have read that these units are probably illegal (too much power) to use in the US without a license. I have also read that they are cheaply made and that they may stray outside their frequency bands. I don't know anything about these items-maybe someone has had some direct experience with them. Maybe someone has another suggestion for a transmitter/receiver pair.

I really don't know how much transmitter power I would need to access all the areas of my building. The building is 150 ft by 150 ft with concrete tilt up walls on the four sides. The internal walls are constructed using 2x4s with sheet rock covering. There is lots of fluorescent lighting throughout the building.

I have been thinking about using a 1.2 GHz transmitter/receiver pair. This seems like a good frequency since it won't conflict with 2.4 GHz portable phones, and WiFi. Does this seem like a good choice?

My intent here is to be legal though not fanatical. I do understand that amateur licenses are not too difficult to get (I do have an EE degree but I never studied radio transmission-though I am interested). If I did get a license, I could operate more powerful transmitters-though it is hard for me to know if this is overkill.

Some suggestions from knowledgeable individuals would be appreciated.

Thanks, Greg Laird

Reply to
glaird
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My suggestion would be for you to investigate spread spectrum wireless technology, where no license is required, and it can bounce a video signal clear across Boston where it is extensively used on television monitoring of the traffic flow on our Central Artery and Tunnel system.

When we built the CA&T, spread spectrum equipment was quite expensive, but today that same technology is available dirt cheap.

Harry C.

Reply to
hhc314

Hi Harry, Thanks for your suggestion--which I think is a good one. I have looked around on the web and found lots of spread spectrum transmitter/receiver devices. I can't seem to find any that are designed for ntsc video--they do rs232, ethernet, various other serial formats. I have looked around for a ntsc to serial converter and then a serial to ntsc for the other end. I haven't been able to find such an item--though I would imagine it would be common.

Do you have any pointers to spread spectrum video tranceivers, or video to serial encoders/decoders?

Thanks again for your help, Greg Laird

Reply to
glaird

I myself have never seen spread spectrum video transmitter devices. Real time video needs a lot of bandwidth and power dispersion.

You will not really know if the system you want will do the job without testing it. High frequencies can easily be blocked by walls, depending on their thickness and required distance. If the unit has high enough power, is should be able to penetrate a near by wall.

As for license requirements, anything that can transmit a signal through the air, and has a rating over the legal limit, is subject to have an operation permit. For any device that can transmit an RF signal through the air, requires to meet very strict standards. If the signal interferes with emergency or essential services in the area, the user will be held responsible.

In your case, if your building is in an industrial area, and if you are going to only use it for a short period of time once in a while, there is probably very little chance of having any type of problem to use a small RF transmission device. As for the FCC or DOC, depending where you are, they usually will only respond if there is a complaint.

--

JANA
_____


 wrote in message 
news:1148770934.802071.48390@j33g2000cwa.googlegroups.com...
Hi Harry,
Thanks for your suggestion--which I think is a good one.  I have looked
around on the web and found lots of spread spectrum
transmitter/receiver devices.  I can't seem to find any that are
designed for ntsc video--they do rs232, ethernet, various other serial
formats.  I have looked around for a ntsc to serial converter and then
a serial to ntsc for the other end.  I haven't been able to find such
an item--though I would imagine it would be common.

Do you have any pointers to spread spectrum video tranceivers, or video
to serial encoders/decoders?

Thanks again for your help,
Greg Laird
Reply to
JANA

how about using a webcam (or pc with a capture card?) and a wireless network to a borrowed laptop pc, or (considering that the service is only needed infrequently) a pair of cellular phones that do video?

It's not like you need broadcast quality video to aim a security camera.

Bye. Jasen

Reply to
Jasen Betts

Jason, I was simply posting what my experience is, and not why spread spectrum is now being widely uses for video transmissions.

I really am not very interested in where and how the video originates, only in its transmission. The advantages of spread spectrum include virtual elimination of multipath effects (which was a real problem in the early 420-Mhz amateur TV days), and license free communication.

It's honestly a hard concept for a non-engineer to grasp, since it depends on spectral dispersion of the signal in a pre-assigned statistical manner, which makes for great communication at high bandwiths, and is virtually undetectable unless you have receiving equipment that has the same frequency shifting key and algorithm as the transmitter. On top of this, a 5-mile link range is relatively easy to achive, and inexpensively. This makes it the choice of most new highway surveilance video systems and many remote control applications.

Harry C.

Reply to
hhc314

These are all good suggestions. I did spend some time looking around for a spread-spectrum wireless video transmitter/receiver and had no luck. As JANA said these sorts of items are hard to find so I have given up on this approach. I do like the idea though.

Jansen's suggestion is also interesting. I do have a wireless network in the building. I looked at PC video capture cards and have found quite a few. Some issues with this approach--it was not clear to me what sort of software I would have to run on my Linux sytem to source the video frames over the wireless network. Then, what would I have to run on my laptop to view the frames.

Also, I am sort of uncomfortable about taking my laptop to the top of a ladder for camera adjustments--I imagine that I would drop it for sure! I did think about finding some little cheap PDA to view images with, but I don't know exactly what to look for.

So, now I am back to my origional idea of using a simple transmitter/receiver comination like the ones sold on eBay. I have a small NTSC LCD video monitor to use for viewing. JANA is correct, my building is in an industrial area and I will be using the transmitter for short periods of time infrequently. If I put the antenna indoors, there probably won't be that much radiation outside the building--so I probably won't be bothering anyone.

The question I now have is what frequency would be a good choice? I have been thinking about a 1.2 GHz frequency so I won't bother portable phones or WiFi. Is this a good choice? How about power--1 Watt, 1.5 Watts?

Best to you, Greg Laird

Reply to
glaird

there's linux packages to get frames and video streams from various different capture cards and usb cameras etc and to serve the stream them over the web.

find the software first and then pick hardware.

vlc (video lan client) would be one package you could use to view the images. AFAIK there's a windows and a linux version.

maybe some way to strap it to your chest, then it's hands free. you just need to open the lid and look down.

it's probably possible to serve it as a series of static images updated every few seconds. any PDA that can view web pages containing graphics should vbe able to handle that.

Bye. Jasen

Reply to
Jasen Betts

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