Looking for a reilable way to transmit composit video  - Page 1
Forum section: electronics / beginners

author: tomy983
author_rank: Contributor
timestamp: September 14, 2016, 06:03:06 pm
content: Hi!This friend of mine who does forest wok asked me to help him set up a CCTV installation.The requirements1 camera, 1 monitorTransmission distance anywhere between 200 meters and 2 km (it varies)Preferred way is rf link12v operation (car battery, alternator)Needs to be sort of portable (40 kg is still fine)Cheapest is betterThe difficultiesThis camera will serve the operator of a large winch which pulls the trees up or down a mountain side. It should help him see if a person is clear from the hook before lowering it and generally would serve as a huge safety improvement .The line is moved about once per weekThe terrain is of the worst, up and down, lots of vegetation and would be impossible to have a line of sight.What I have tried1.2GHz and 900 MHz video Tx Rx about 800mW of power with omnidirectional antenna, with no luck.What I thought might workArmoured fiber optic linkIs coaxial possible at 2Km?Helium balloon to raise 20 meters the TxIs there a way to make a steel cable act as a transmission line?Well, here I am looking for suggestions on how to make this link... how would you do?

author: dmills
author_rank: Super Contributor
timestamp: September 15, 2016, 09:13:47 am
content: UHF is always basically line of sight, so that is probably a non starter.RF over cheap satellite coax?Advantage is that the cable is very cheap and effectively disposable, and the RF means you should not get into issues with cable compensation as the bandwidth is small compared to the operating frequency.Analogue modulators should be readily available surplus from CATV upgrades as should appropriate distro amplifiers.Get an old telly that does NTSC with an RF input, job done.The alternative is really fibre, easiest to start with a digital SDI signal in that case, as there are all sorts of converter boxes available in that space, warning from experience, critters will eat fibre jacket unless you get the right stuff.If you go for fibre, do keep the stuff on a professional cable drum (The stuff has a minimum bend radius and means it) and do protect the ends when it is not in use, the extra cost of expanded beam connectors may be worth it for reduced cleaning issues.Regards, Dan.

author: tatus1969
author_rank: Super Contributor
timestamp: September 15, 2016, 11:12:27 am
content: I cannot point to specific products, but I know that the quad copter community has quite some evolution in in-flight live video streaming. I have seen them building links in the km range, streaming that directly into a VR helmet. Very impressive.

author: dmills
author_rank: Super Contributor
timestamp: September 15, 2016, 02:31:43 pm
content: Yea, but they have line of sight, it makes a HUGE difference at UHF and up.The only way RF is really going to work here is if you can put a repeater somewhere in sight of both locations (Or use a truely stupid amount of power).Regards, Dan.

author: Kilrah
author_rank: Unknown
timestamp: September 15, 2016, 02:40:15 pm
content: Quote from: tatus1969 on September 15, 2016, 11:12:27 amWhat he's tried (and doesn't work) is basically the top end of what we tend to use for that.For having been in that field for more than a decade there will be no RF-based solution other than what dmills says in the post above.

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 15, 2016, 03:12:51 pm
content: Quote from: tomy983 on September 14, 2016, 06:03:06 pm+1. if necessary, Rx too...