Voltage Reference Between Multiple TV Antenna Inputs

http://www.aerialsandtv.com/ampsandsplitters.html#Splitters

http://www.digitalspy.co.uk/forums/showthread.php?t=398723

ideal should be separate cable from each tv to a central distrubution point.

unable to find any isolated splitters, although if the out covering was to be isolated the screening effect of coax would be lost.

the coax needs eathing at both ends.

if apartment has wall plate for tv to be plugged into the outer screen sould be earhed here, and not just at airiel end.

if the chassis of tv is live these should be allowed to be used.

Thank you for your prompt reply.

The apartment is 50 years old. Therefore there's no wall outlets available. Cable is directly comes to the aerial of the TV set.

2. Central distribution point is unearthed.

3. I am officially not allowed to make the Central distribution point earthed.

Because it is not mine, it belongs to municipality.

3. Unearthed distribution point is the main reason, of which it's outer body is carrying voltage, injected from someone else's TV set.

Therefore my aerial cable coming from the distribution point brings me voltage.

The only other way would be to Make up some shield isolation cables.

or Ground loop isolation device

the first link has some good info on your problem

http://www.epanorama.net/documents/groundloop/antenna_isolator_building.html

http://www.uspystore.com/coaxial-video-ground-loop-fault-isolator.html

http://www.amazon.com/VSIS-EU-Cable-Ground-Loop-Isolator/dp/B0017I3K9M

http://www.digitalspy.co.uk/forums/showthread.php?p=3265910

http://www.google.co.uk/search?q=tv+coax+ground+loop+isolator&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&redir_esc=&ei=gvvaS_T7F5f20gTvo9yEBg

Thank you peterg7lyq

I will try to build a 1:1 transformer as explained in your Link#1

I will let you know when completed.

The point I am verifying in my mind that I have three units of TV sets n my house in 3 different locations.

Can I use a single 1:1 insulating transformer at the aerial cable entrance to my house and distribute the output to each TV.

(However if not, I can amplify the output before distribution. I already have a simple boadband amplifier somewhere under my hand )

It is ridiculous, the Cable TV network provider is offering me if I accept buying their digital decoder to switch the encrypted digital broadcastings, since I am scaring to blow up my TV set, of 4000 USD, due their faulty network.

Kindest Regards.

as long as you are sure your TV`s are ok.

just isolate incoming coax then distribute to your 3 TVs.

good luck

do you have access to the distribution box or the other tvs ?

reason there are two ideas that spring to mind now i think about it.

some tv`s mine included hav a facility on the setup of the tv accesed via the remote control, To send power up the coax to power mast head amplifiers. this was intended for single coax feeds from the TV directly to the Mast head amplifier.

It was never intended to go via a distribution splitter.

the other thing you could try is to break or carefully cut the outer braid of the coax either where it goes into the TVs or at the distribution box which ever is eaiser.

easiest way is to unplug coax remove about 1 inch of outer plastic to revele braiding and carefully remove or cut this so it is no longer connected, then cover with insulation tape.

Doing the cut method will break the cicuit of the outer braid the coax should still perfom its function so long as one end of the coax is left attached so only cut one end.

In the USA, I believe the incoming splitter is required by law to be grounded (although many are not). If the Incoming splitter is grounded, then the shields of the cables going to the intermediate splitters and all the TV sets should also be grounded, simply by being connected to the coax (it IS coax, isn't it?).

It sounds like you need fuses in every connection. I don't know how that could be done without degrading the signal, but if you are getting currents large enough to melt plastic, then you have a significant safety problem, both in terms of personal shock, and in terms of possible fire. You are also wasting significant energy.

My guess is that there is a single defective TV somewhere in the building that is causing the problem

Exactly. I agree abt. a defective TV somewhere in the building, or somewhere around. in someone's house, I am not able to access.

I remarked one unclear point in my previous explanations. Now I am clearing hereby.

I am getting large circulating currents to melt the plastic insulation of the coax cable. Upon remarking the sparks, I got checked the amount of the difference voltage by multitester. I read 27 to 32 Volts. (across the aerial input of m TV set and the coax cable connector)

Regarding your questions,

1. Yes the cable is Coaxial as usual in the broadband TV aerial connections.

2. The house and the plugs are correctly fused, complying the international safety standards. No particular fuse reserved only for TV. And as appreciated using an earth leakage protector is not possible in this leaking case.

I could only imagine any type of insulating coupler. (Such as an opto-coupler or an electromagnetic coupler to block the circulating current ouside of my house, to be placed at the point of entrance, of which the aerial coax cable to enter in my house.

Kindest Regards

Nezih

GA, except that only version A is safe. With the plastic melting, it's almost certainly a large current in the shield. Although version C would stop the shield current, any inductive splitters or baluns connected would then transfer the current to the center conductor.

Thats why "A" was "A" so to say......and not "B" or "C"......well checked out!!

Thanks for the GA by the way, but the fix was so simple, I am not even sure I earned it really....

Better than $100 transformers and the like don't you think? and far far cheaper if you do it yourself.

Thanks Andy. I will make a trial as soon as possible.

I will cut the aeral at the entrance point in my house. And place a jonction box, of which two coax. connectors in each sides.

Then will connect the shield to other side's shield via capacitor,

An also the live to live via an another adjacent capacitor.

Hope this will block the high circulating current of approx. 30 VAC between the distribution center and my TV set.

I believe that even I will receive the 30VAC, 50Hz reference voltage, binded over the TV signal at the TV side, My TV set will be deaf for 50 Hz signals and only evaluate the HF broadcasting

Kindest Regars

GA

As it happens, I did some TV repair work in S-E Europe. Many TV sets were with live chassis, so the solution of the designer was to use two xxpF capacitors/1000V to galvanically separate the TV set and antena cable.

SPlitting a TV signal more than one time is a recipe for terrible viewing. I always used multi-channel distribution amps to do that. If you can ground the plug of the distribution amp, you will probably get rid of the ground loops you are chasing.

Kramer makes a good 1-in/4-out amp for around $ 100 USA:

http://www.fullcompass.com/product/269739.html

Thank you for your comment in the matter of grounding the distribution amp.

I did this trial. obtained no success as mentioned below.

Once I placed an antenna amp has one input and one output. Then splitted the amplified output to 3 units of TV sets. Of course I grounded the both shields.

The problem occured when grounding. Incoming cable got warmed.

Because incoming cable is carrying 30VAC in reference to my earth.

The outer distribution center, of which I am not authorized to intervene, is receiving a leakage.voltage from a defective TV in any building, and brings it to my house, via the aerial (coax.)cables. Since the consierable ohmic resistance of the long aerials, the circulating current is being limited. Therefore not blowing the defective TV, but the current is enough to melt the plastic insulations of the cables when grounded.

Kindest Regards

TVs, at least in Europe are always 2 wire, no ground, so they have no reference to ground and the earth connection on the antenna can quite often have a "feelable" AC voltage on it....noticed it on many TVs over the years. I would go so far as to say almost unavoidable....but bad news when you have a communal antenna system.....

Some Sat receivers seem to do the same thing.......the only fix I have found is to use a camping receiver that takes only 12 volts DC.....but that won't fix the TVs unless they are also 12 volt with a "wall wart" too.....

Try the caps fix I posted.....

Thanks to interest of all guys for their useful ideas for solution given in this thread.

Recently produced Far East TV sets are built grounded chassis.

The ones I have are A Hyundai Electronics LCD and a Samsung LED 6 Series. Both are grounded.

Since other TV sets in the neigbour's houses are 2 wire and no ground, they can be considered live chassis.

They should be injecting a feelable AC voltage to the common CaTV system, not harmful, but only producing diagonal lines on the screen at the weak stations.

But this is a different case. The current is not only feelable, but carrying high currents to heat the shield the coax. cable. Possibly because of a defect TV set.

Now today I made an experiment. First I decided to try the insulation transformer solution.

I bought a Balun. You know it's a transformer. One side is 300 ohm's of impedance, and the other side is 75 ohm as standard.

However I could not find an insulating type in the markets. There is connection between both windings.

(This means no use to make two baluns first converting 75 ohms to 300 then re converting 300 to 75 ohms to obtain an insulation. Entire terminals are condutive to each other.)

Therefore I removed the connections between four loops, each are 150 ohms.

Connected two loops parallel to obtain 75 ohms. (They were already paralleled.)

The remaining two loops were (150+150=300)serial connected. I converted them to be parallel 75 ohm.

Now the primary and secondary loops were independent from each other, of which there is no ohmic connection between them

Therefore I obtaned a 75 ohm to 75 ohm insulated transformer.

I then checked how useful is this magnetic coupling.

I can tell that the insulation is O K. However %20 of signal loss at output. strong stations are good. but some weak stations are gradually noisy.

Since insultion problem is solved, it is not problem to amplify the output, with a broadband amplifier, of which I already have. Therefore this is a kind of solution.

I will try the capacitor method tomorrow.

Kind regards.

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