the toss

Pure copper conductors , >95% shielding , 0.9mm centre conductor

You can get DVR's designed for vehicular use (taxis , buses etc) at a reasonable price. This will give you everything you need , multi camera display , recording etc

If you are responsible for building that then you should be proud - a beauiful piece of work

70% of a commercial balun in terms of physical size is the BNC connector and the housing. Why not get a commercial balun and de-construct it then just use the circuitry to install in your available space in the camera.

As a general calculation you would assume each camera used would require 1amp. So 8 cameras = 8 amps So either of those supplies would be OK. The current rating on a supply is only an indication of what it is capable of supplying

It will not be static (where would static come from ? ) Much more likely to be an earth potential differential.

still useable as a dummy camera

I dont really understand your connection explaination. When you say " via ethernet " are you saying they are networked or are they just using cat 5/6 cable ??

It is hard to say without more info. If it is 20awg 95% "pure copper" then 41^ seems a bit high. The 10dB loss would depend on what frequency it is measured. If you swept a cable from 1Mhz to 1Ghz the attenuation would vary from about 2dB @ 1Mhz to 40 dB @ 1Ghz over 100m

1) short inner to outer at one end and measure DC ^ at other ( return loss ) You will need to know your cable type/specs which may present a problem if it's not your cable and has been buried

Its probably a bit late now but CVI ( and probably TVI) will run out to 500m. Have you done a DC resistance measurement to check those joins??

If it is good quality coax you should have no problems over 1000'. It should have been done properly in the first place with no joins

I would be revising your understanding of your laws cause that has to be the weirdest statement I've seen in a long time. EVERYTHING the camera is viewing is in line of sight else it wouldn't be viewing it.

This would depend entirely on the laws for your location. Where I am any action that is for the purpose of intimidation , harrassment , causes offence or duress would put you in trouble. I'm willing to bet that your neighbour would (rightly or wrongly) have a similar story to tell about you. Why dont you talk to them and if a solution cant be worked out then just agree to stay out of each other face

There are plenty of units available fairly cheaply but they have their limitations and you are going to have to power them (and the camera ) somehow. These units are advertised as 4 channel but keep in mind that they are really "one of four channels". You cannot plug 4 cameras into it but only select one of the available 4 channels to use. This is to give frequency diversification in case of an interference issue. I have used one in the past to find out why so many eggs were broken in the chookhouse. Turned out to be a cannibal hen who ended up tasting really good with baked potatoes and pepper sauce. While they have a use please remember that they are essentially a hobbiest item and not something you should put any degree of faith in. You will have continuous signal dropout issues (especially when raining) as the signal path is short range line of sight

Sounds right to me

Why on earth would you use motion activation on an outdoor camera to trigger email/sms alerts. You now have first hand knowledge of why it shouldn't be done.

It may be a case of semantics but most electronic devices will not run on reversed voltage. BUT they CAN be designed to accept a reverse voltage input. A simple full wave rectifier will correct any reverse voltage and offer up the correct polarity to the device. This is how dual voltage cameras work. This is a cheap and common form of protection in quality electronic devices but I would not expect it to be in cheap cameras where cost have been cut to the bone.

Even cheap kits can do a reasonable job but as Tom has suggested a cheap kit running on cheap unsuitable cable is a recipie for dissappointment. While I'm not a big fan of cat cable because of its poor physical integrity, it can certainly come to its own if you have a few cameras co-located. In Aust there is a standard that conduit should not be more than 40% filled.

Its not hard to make your own. A piece of aluminium angle , drill your holes , fit BNC male-male panel mounts and there it is.

Fault finding 101. You have 1 camera working fine. Swap out the other 6 cameras in place of the camera that is working. They should ALL work on that position. Those that dont are faulty. Now that you have tested the cameras are good get one working and then swap it onto other channels at the DVR. Any that stop working indicate a faulty channel input on the DVR. You would hope there are not 6 faulty channels but...... Now that leaves only the cables. Pick an input that you have tested as good and pick a camera that you have tested as good. Test each cable using the known (good) channel and a known (good) camera. Any that dont work is faulty. When using baluns and CatXX cable you can only use ONE twisted pair for the video signal. You CANNOT split the pair and you CANNOT double up with another pair

Now there is a problem waiting to happen. It has always been a standard to have the tip positive and the sleeve negative. You would want to hope there are protection diodes in the power circuitry. Nevertheless you can do what you suggest but if the cameras have IR then a 1A supply probably wont be enough to do the job at night

I might be a bit picky but RJ45 is a name for termination hardware not a type of cable. I think it is important to have the terminology correct

Your BIGGEST problem is wanting 24/7 reliability AND wireless in the same package

As Rossko has pointed out the 12V is a nominal working voltage and you will likely find that anywhere from 10 -14 V it will work fine. I'm intrigued about the statement that a diode will cause voltage fluctuations - can you elaborate