Video Quality Difference On Handheld Monitor And Dvr

[owillingham]

Hello, this is my first post in the forum. I'm an electrician by trade but do alot of cctv work for my customers aswell. I'm currently doing some work on a horticultural nursery, I have installed a camera to cover their diesel tank as they spend £1000 a week refilling it for the use of their vehicles, and they have reason to believe diesel is stolen on a regular basis. Due to the nature of the business huge distances are involved and the diesel tank is the best part of a kilometer from the office where the dvr is installed, and there is a hill and plenty of trees in the way aswell so no direct line of sight. I brought a wireless sender and reciever kit through ebay direct from china that claims up to 2km range with direct line of sight. I also brought a couple of Yagi high gain aerials from another seller (again direct from china) in order to maximise the range of the system. After installing the camera and transmitter I found that the signal wouldnt reach the office with a stable image but would reach a large shed approximately 150mtrs away, as I had already run cat5e cables to the shed for other cameras already in operation I decided to mount the reciever here. I then put a balun on the output of the reciever and used an unused pair from one of the existing cat5e cable to the office where I put another balun on the cable. When I watch the picture on my handheld test monitor (for use in setting up/focusing cameras etc) I get a stable image, theres a little interference (white horizontal lines) but the image is acceptable. But when I put the balun onto the back of the dvr and look at the image on the main monitor it either reads no signal or a picture that is so poor and distorted you barely tell what it is. Obviously there has been alot of install time and cost involved already so i'm not looking for a new approach (though any recomendations on how I should do it in future instead would be appreciated) but simply a quickfix solution to the difference in video quality between watching on my handheld monitor and going through the dvr. I'm assuming that perhaps my handheld monitor has built in filters/booster for the signal or perhaps its something to do with the electrical phase that the dvr is on and the phase that either the transmitter or reciever is on. (there are various electrical supplies over the site, I cant change the phase as most supplies are single phase but on different phases), and the phases not matching - obviously this wouldnt affect my handheld monitor as its battery powered. Is there any kind of image enhancer/filter/converter or such that may help with my problem? Many thanks in advance. owen.

[james.wilson]

what is the length of the cat 5 run and what baluns you using and what is the dvr?

chinese stuff is generally tat but first id get your cat5 link running right

[Alarm Protection]

Does the receiver have signal strength light on it to see if they are good/bad etc? White lines may be signal or as you say phase problems.

As James says it could be rubbish baluns.

If you have a picture at the receiver you could boost the signal using an active transmitter but 150 mtrs should do the job with baluns either side and an active may be to strong for it.

Next time buy from a local supplier though as some of the stuff the Chinese claim their equipment does is lies.

What happens if one of the transmitter/receiver develops a fault?

[owillingham]

not sure why my last reply didnt come up, but the interference (white lines) is from the wireless leg of the journey as I get it when plugged straight into the reciever.  I can live with this as its the best part of 1km in distance with a fair amount of obstacles.  I have since brought 3 more in case I need spare or a similar set-up.  The baluns are the cheapest of the cheap from china, but I have used loads without any problems, and as its only 150mtrs and the signal on my handheld is the same as it is next to the reciever i'm happy with the cat5 part.  The dvr is a prokam, I've got one in my house aswell and I really like them, they are a budget dvr but a goon one, i've tried a few different ones and there certainly are some rubbish dvrs out there.  I do tend to buy cameras etc from uk suppliers, but connectors, bnc crimps, adaptors, baluns etc i just buy in bulk from china as I dont think the cost difference in buying from western companies is justified.  I brought the wireless kit from china as it was incredibly cheap (£40 plus and extra £25 for the two aerials).  It would have cost hundreds to buy a similar kit localy and as I wasnt sure it would even work I thought I'd just experiment with the cheap option, which in honesty i'm very impressed with and as I said have since brought 3 more.

[owillingham]

Sorry forgot to mention there isnt a signal meter on the dvr to say whether the signal is good or bad, but thinking about it I could have used the colorbar generator on my handheld monitor to test the cat5 leg up to the dvr, not sure why I didnt do that but will do when i'm up there next week just to confirm the integrity of the cat5/baluns though I have a gut feeling this will work out fine as other camera images are going through the same cat5 on baluns with no problems.

[james.wilson]

Ok but your putting a far weaker signal into your cat 5 due to the cheap radio stuff. I also would class the i/f as acceptable it will cause you issues later on. You may be able to fix it with a decent active tp reciever.

Cheap stuff even connectors etc will work fine on short runs. When your going beyond that you should imho only use decent kit. No good now I accept.

As its a cheap dvr its probably struggling on the weak sync pulses of the video signal. You are going to need to clear them up. What does your test monitor / scope show the video signal is like?

[owillingham]

I dont have an oscillascope, and my test monitor doesnt have a signal meter either, i really only use it to align and focus cameras when I install them, and occassionaly check the ptz protocol etc.  I admit that any i/f isnt really acceptable but compromises had to be made given the diesel tank location and the unwillingness of the customer to spend much money (I know the argument could be put about money saved on diesel if any culprits are caught but his opinions on cameras is that just having it up there is a deterent whether it works or not, and even if it worked to the best of its ability it wouldnt stop or gain a prosecution of a determined thief).  If you think its a weak signal out of the reciever, is there a signal amp I could try before it goes onto the cat5? Also I'm assume that the dvr expects a line resistance of 75ohm on the input, I havent measure it but going through baluns and wireless kit, is this likely to give a difference resistance and picture (I will put a multimeter on the balun next week to check)

[sixwheeledbeast]

Instead of buying more ****. Get yourself a Signal Level Meter like a Ranger.

You can then check P2P and Sync levels.

Cheap stuff never pays, your forever messing with it to get it working; even connectors.

I am guessing you maybe better with active baluns, video level/gain will be weak at the DVR.

[owillingham]

I've just dug out the instructions for my handheld monitor, and it does give me a video level of the amplitude of the signal measured in mV, I've just tried it now with another camera plugged in but it just seems to go up and down with brightness of the image (eg camera in dark will give low signal level, camera pointing at light will give high signal level).  I'm doubting this level meter will help me determine the problem I'm having, but assuming that I purchase some active baluns, is it just a case of increasing the gain at one end to boost the signal or is there more that I need to do, if it is just case of turning up the gain, can I use my existing monitor or do it by eye?  This is the first time i've had this scenario, and I dont do enough cctv work to justify going out and buying another meter which in all fairness is unlikely to be used again.  I know you think I should forget about buying more ****, but I just need to know why I can see image fine in the office with the balun plugged into my handheld monitor but the same balun plugged into the dvr gives an un-useable image.  If it is just a case that the signal is amplified inside my handheld monitor but it isnt inside the dvr then I just want something to do the trick, either an inline signal amp or the use of active baluns etc.  I get the impression that you think I only buy cheap chinese cr*p, which really isnt the case.  For simple things like dc plugs and baluns (which is essentialy just a magnet with a few coils of cable around it), I do just buy cheap and in bulk otherwise even the smallest of jobs get expensive.  The wireless kit was brought cheap because i was doubtful that wireless would even work and I didnt want to spend bug bucks on a system that I cant sell to the customer and that the customer isnt prepared to pay, it was more of an experimet with wireless to see how it works.  I'm quite happy to buy branded baluns or active baluns if you think it will fix the problem but I'm still confused as to why the image is ok on my battery monitor but not through the dvr.

[james.wilson]

Cos its a cheap and nasty dvr?

You could try pushing more through your wireless link and then equalise at the end, but if you had used proper gear throughout you wouldn't have this problem. What your asking if I can paraphrase. Is how do I make the cheap **** I have work like high end equipment.

In truth you can't but you may be able to mask some of the issues some of the time with active baluns (decent ones) but I would be tempted to try over volting the rf link and then equalising.

Addlestone make some good gear for this or use NVT active gear at the source and the cat 5 bit. Plus how decent is the cat 5, you will IMO always have issues with this but you may get 6 - 12 months this way. You need to make your client aware of this IMO and give them an option cost to do it properly

James