the toss

Your picture is ok where it enters the DVR (as shown by your test monitor) so that would suggest the problem lies with your DVR or VGA monitor. Swap them out to prove which is the culprit.

It looks more to me that your auto iris is stuck in the open position

Where do you source yours from?

There is no way of cheating Mr Ohm

I make it a rule to use 24Vac cameras for anything over 50m. Like CCTVman says - it's all to do with your power.

I will bet that these are 12V cameras - right?

You can do that by using a BNC "T" connector and while it is not technically correct it works perfectly ok

I guess the the real difference in our views is the environment we are thinking in. To me a long transmission line is 300m @9Ghz whereas to you a long transmission line might be 30Km @ 60Hz but since power transfer in an AC electrical distribution network is voltage driven & not current driven I still dont believe skin effect impacts as much as you say.

Skin Depth (>90% Cu) = Sq root of (2r divided by wu)

where r = resistivity w = angular frequency and u = permeability

skin depth = 8.5mm @ 60Hz

skin depth = 0.0066mm @ 100Mhz

as can be seen at 60Hz skin effect is of no consequence until the conductor is > 17mm dia.

Back to the original post and THE main reason to use 24Vac instead of 12Vdc is (just like in electrical distribution systems) the efficiency of power transfer - ie lower voltage drop due to current in a fixed resistance. It also enables voltage rectification & regulation at the load which will negate ANY voltage drop (within reason) over the transmission line

BTW I am a licensed professional electrical engineer with more than 34 years in the electric utility industry as a transmission and substation engineer.

and I am a licensed proffessional RF engineer (with electrical engineering degree) specialising in microwave radio systems ( and where skin effect IS actually relevent ). I think you will find the multi conductor construction of your transmission lines is more to do with mechanical integrity than skin effect.

Skin effect isn't worth considering until you get to 500Mhz or so and it is more about signal propogation than power transfer

For small conductors the AC and DC resistance are the same. On large conductors the AC resistance is higher due to the skin effect which does not allow correct to flow in the center of the conductor. That is why power lines use multi conductor wire so as to increase the surface area. DC current can flow through the entire conductor so for a same size large conductor you will have less resistance with DC than AC.

 

I am not discussing AC impedance (capacitance and inductance) since this does not become an issue over short distances.

 

For household AC and low voltage DC applications the DC resistance can be used to calculate voltage drop and the voltage drop will be identical whether you are using AC or DC for a given voltage.

Skin effect is virtually non existant at 50/60Hz and can be ignored

There is not much you can do - it is working as it's designed to

So why is 16mm lens the biggest? Are they relying on the fact that being HD the digital zoom can do the job of large lens's. If that is the case why have ANY HD camera with a varifocal lens

Any such thing as a HD analogue box camera that can have the lens changed to what is required ? thanks in advance

Up til now any installation of HD analogue cameras has been pretty run of the mill domestic or small commecial. But I have a job upgrading an existing system of 42 cameras in a fairly large distribution warehouse. The existing system utilises some specialist cameras besides general overview of other areas. There are two NPR cameras running 60mm lens's for close ups of number plates from a mounting position 100m back from the gates. There are three used for item tracking on the loading conveyor system. These cameras are not only recorded but used in real time on a day to day basis. ie the number plates are manually logged and approved for entry to the site before the gate is opened. Therefore the digital zoom on playback is of little use , what is needed is a realtime close up view of the numberplates as they seek entry. (hence the 60mm lens)

After doing a fairly comprehensive search of distributors in Australia , it seems the only choice of analogue HD cameras (CVI,TVI or AHD) is a fixed 3.8mm lens , a 2.8 - 12mm varifocal , not counting the ptz models. So it seems that a replacement in analogue HD is not available for anything above 12mm.

So what I'm asking is - anybody know where I can get an analogue HD camera with a lens bigger than 12mm ?

BUT (now that I've had breakfast & my mind is working) what we are really talking about is TOTAL capability. You have 19 cameras @ 500mA = 9.5A. Power supply is good for 20A. The distribution over the 18 channels is only done by your 18 x 1A fuses. So you should be able to change one fuse to 1.5 or 2 A and run two cameras off it with no problems.

Maybe - it depends on how your power supply is designed. On a simplistic level you have a 20A supply split over 18 channels. That gives a smidgen over 1A / chan. Your cameras require 0.5A each so in theory you could (just) run 2 cameras on one channel but you are sailing close to the wind. The other problem is the built in protection. If it is a fuse per chan then you may need to up the size but if it is PTC protection then you may need to get the soldering iron out. The better way would be to buy a smps to run the 19th camera

Dont understand how you are getting your PoE to the cameras without running cables to them

Chase up cable suppliers. I get RG59 in 500m rolls. Siamese in 300m rolls

The dark clouds are breaking and the storm beginning. France then who, Germany or Sweden?

I dont want to turn this into a "my dong is bigger than your dong" session. Why do you think Belden make so many coax cables that are only "slightly" different. (as you put it ). What is the difference between RG58 & RG59. By your train of thinking one is slightly thicker than the other and thats it. But I know that you are knowledgable enough to know better. So what is it that makes one have a Zo of 50^ and the other have a Zo of 75^. They look the same , they both can terminate in BNC connectors , cut them open and its hard to see a difference other than overall diameter. Its pretty much going the other way from comparing rg59 and RG6. The centre conductor may be smaller but that apparently doesn't make much difference other than to dc resistance and attenuation according to you. But I know that you wouldn't use RG58 for CCTV and RG59 for your CB radio.

If you look at dc & ac equivalent circuits that represent the characteristics of coax cable there is a thing called radial transconductance and radial transcapacitance and this is extremely important when calculating the TE11 propogation characteristics. Now I'm not an expert on coax cable design but I know a fair bit on the effects of that design on HF (microwave) signals. I can try to explain it as I understand it but if you asked any difficult questions I probably wouldn't be qualified to answer them.

I cannot comment on any of this if we talk digital signals - I am a child of the analogue age.

Great stuff - you have proved my point. While West Penn call these cables RG6 , RG11 , RG59 almost everybody else would call them long range RG59 , extra long range RG59 and standard RG59 because ALL they are is RG59 with different size centre conductors resulting in lower dc resistance and signal attenuation. When you look at a real set of electrical specs you will find that TE11 signal propagation , slew rate and signal velocity factor are ALL very different between "REAL" RG6 , RG11 & RG59 and I'm surprised that West Penn have not been challenged over their marketing practices. Having said that it is increasingly obvious that coax specs seem to be at the mercy of the marketing industry for a number of years and no one seems to do anything about it.

Another common example of the specification barstardisation it the 3" speakers capable of handling 100w. They neglect to mention it is 100 PIMP (peak instantaneous music power) which in real life is meaningless.

So survtech - cable aint cables especially if it is West Penn cable

Seriously? They are not RG59 by any stretch of the imagination.

 

A cable's "RG" designation is a function of the impedance, the diameter of the center conductor and the spacing between inner and outer wires, not the actual materials used in its manufacture. The RG designations are a vestige of an old military numbering system dating from World War 2. "RG" designates the term "Radio Guide" and the "U" signifies "Uniform" or "Universal". They are mostly used to identify compatible connectors that fit the inner conductor, dielectric, and jacket dimensions of the old RG-series cables.

 

Still, calling CCTV-compatible RG6 "long range RG59" is like calling a Boeing 777 a "long range DC-3". RG59, no matter its construction materials and use, has a center conductor ranging from 23 gauge to 20 gauge, depending on the manufacturer. RG6 has an 18 gauge center conductor and RG11 has a 14 gauge center conductor. The major difference between low frequency cables and high frequency cables is the construction of both the center conductor and the shield. LF cables typically have pure copper center conductors and shield while HF cables typically use copper-clad steel or aluminum or some combination of the two.

 

HF cables also commonly use a foil shield and an integral drain wire. The main reasons for the differences in component materials and type of shield are the cost to produce (and sell) and the properties of the signals the cable is meant to carry. Steel and aluminum are substantially cheaper than copper and even adding the cladding and/or tinning process adds less to component costs than using pure copper. In fact, there are some types of hard cables that have hollow center conductors for that very reason - to save the unnecessary cost of the "missing" copper.

 

The second reason for using clad wire vs. solid copper has to to with DC and AC resistance and the "skin effect". LF signals travel totally within the diameter of a wire, so if the inner part is made of steel or aluminum, which both have far higher resistance per foot than copper (or hollow), the signal would suffer greater attenuation and would deteriorate relatively quickly. HF signals ride on the outside of a conductor, something called the "skin effect". Because of that, it is not necessary to use solid copper conductors for CATV because the inner copper part of each wire (including the individual strands of the shield) is unused. In fact, the hollow center conductor of certain "hard cable" types for HF signals is actually a plus. Due to the skin effect, the signal only travels on or near the outer surface and the higher the frequency, the shallower into the cable cross section the signal travels. Hollow wires have both the inner and outer surfaces to ride on and the inner surface adds surface area, lowering the attenuation.

 

You shouldn't use CATV or RF-rated non-pure-copper-conductor cables for LF signals for that specific reason. It can be acceptable for short distances but not longer. Copper/copper RG59, for instance, can transport video signals up to 1,000 feet but I wouldn't use clad cable for distances longer than maybe 200 feet, if that. The specs of the two types of construction say it all. For instance, West Penn 841 and 6100 are almost exactly the same except for the construction of the center conductor. 841 has a solid bare copper inner conductor, which yields a DC resistance of 6.5 ohms per 1,000 feet while 6100, which has exactly the same specs but with a copper-clad steel inner conductor, has a DC resistance of 28 ohms per 1,000 feet. If a 6.5 ohm/k resistance yields a maximum distance rating of 1,000 feet, a 28 ohm DC resistance would yield a maximum distance rating of around 230 feet.

 

Finally, I use West Penn's catalog as a reference because it is simple, yet comprehensive. Belden and other wire manufacturers agree with the gist of what W/P says, only their catalogs are not laid out as simply. Belden, in particular, manufactures so many variations of cables and their documentation leaves so much to be desired that it is almost impossible to pick a cable without spending a huge amount of time digging through their catalog and translating their specs. I don't know why you equate West Penn's specs with a speaker manufacturer's over-inflated power rating. Do you also compare the horsepower of cars to the flavor of beers?

Just about all coax can be got in CCA, CCS and Cu and that is not what we are talking about. We are talking about WHAT distinguishes one type of coax from another. You seem to think it is centre conductor size and I'm trying to tell you it is SO much more. You last paragraph actually sums it up for me. West Penns catalogue IS NOT comprehensive at all and is actually dumbed down to cater for people who cant comprehend specifications. This is amply demonstrated by comparing to the Belden catalogue (as you yourself point out). I suppose you must think Belden does this just for the fun of it.

Please dont diminish yourself by using stupid comparrisons of beer & cars. The loudspeaker reference was an example of the barstardisation of technical specifications to suit the marketing industry. I thought you would be capabale of understanding that.

Pirs as used on sensor lights are total junk. The are many grades available as any security technician will tell you. The are PIRs specifically designed for outdoor use and you should stick to these. I usually use the Bosch OD850-F1 but Optex & Rockonet also make excellent PIRs

Great stuff - you have proved my point. While West Penn call these cables RG6 , RG11 , RG59 almost everybody else would call them long range RG59 , extra long range RG59 and standard RG59 because ALL they are is RG59 with different size centre conductors resulting in lower dc resistance and signal attenuation. When you look at a real set of electrical specs you will find that TE11 signal propagation , slew rate and signal velocity factor are ALL very different between "REAL" RG6 , RG11 & RG59 and I'm surprised that West Penn have not been challenged over their marketing practices. Having said that it is increasingly obvious that coax specs seem to be at the mercy of the marketing industry for a number of years and no one seems to do anything about it.

Another common example of the specification barstardisation it the 3" speakers capable of handling 100w. They neglect to mention it is 100 PIMP (peak instantaneous music power) which in real life is meaningless.

So survtech - cable aint cables especially if it is West Penn cable

answer me this servtech - what is it that distinguishes RG6 , RG11 & RG59 from each other? Now if you look at the very limited specifications on your West Penn link then you would have to say it is the centre conductor guage because that is the only difference between the 3 according to West Penn . I shall look at your other references shortly as well as try to find you some good bedtime coax stories to read.

I said - " it may or may not work for your application"

I Didnt say - "RG11 is coax but no good at all for CCTV " (tom said that )

Thank you for your replay

 

There is a coaxial cable called RJ11

RJ59 will not have a clean picture over 300m is this true?

I believe you meant RG11, not RJ11. Also, it's not necessarily true that RG6 is not suitable for CCTV. With any type of coaxial cable, the capability to transport video signals is determined as much by cable construction as it is by cable size/type.

 

For best CCTV results with coax cable, it should have 100% pure copper center conductor, not copper-clad steel or aluminum. The cable should also have a shield made of woven pure copper, covering at least 95% of the inner core. That cable is typically referred to as copper/copper or bare copper. Cables with the designation "CCA" (copper-clad aluminum) or "CCS" (copper-clad steel) have limited usefulness for CCTV. The reason being that an analog CCTV signal needs pure copper for best performance / longest distance. Coaxial cables for CCTV can have additional shielding, but the primary shield must be pure copper and cover at least 95%.

 

You can obtain RG59, RG6 and RG11 with either pure copper or copper-clad construction. Clad cable is primarily used to transport HF (high frequency) signals like Broadcast or Cable TV, radio and other RF signals. Pure copper cable is used to transport low frequency signals like baseband video, audio and some types of data. If you choose bare copper, the distance capabilities without mid-span amplification and/or signal correction are:

 

RG59 - up to 1,000 feet / 300M - 20 gauge center conductor (Example: West Penn 825)

RG6 - up to 1,600 feet / 500M - 18 gauge center conductor (Example: West Penn 806)

RG11 - up to 2,000 feet / 600M - 14 gauge center conductor (Example: West Penn 811)

 

The above table is for copper/copper cable. Distance capability is drastically reduced for other types. As with any type of cabling, the correct termination (connectors) is required for best results and good practice must be followed when installing the cable (no cuts or kinks, installation following proper "bend radius" requirements, etc.).

That is what I said AND you wont know til you've done the work installing it. But I am not talking about the signal transmission capability I am taking EMI rejection at CCTV frequencies.