View Full Version : self install - tv/fm isolator required/what is it?
Hello there
I've just installed my new VM set top box, and at the same time took the opportunity to tidy up some of the messy cabling that had been put in place by the previous owners.
I have removed a wall box (from inside) which contained a very old looking FM/TV isolator, 3 ports on it labeled, IN, FM and TV, it also has written on 5-1000mhz and is made by Vocom (vc300). From the TV port on this box I used to run my broadband modem.
On the outside of this wall sits a splitter box (which gets its feed from the brown NTL box on the other side of the property), one feed goes upstairs (now where the broadband modem sits) and the other now goes inside directly to the TV.
Everything seems fine and works well as it did before.
I am just wondering though whether the FM/TV isolator is required or not, and what is it? I'm guessing something to separate TV and FM equipment so that they do not interfere? Doesn't seem to be any interference with the cable modem/set top box, so is it ok to have this set up, or should I be putting the isolator back?
Cheers for any advice.
Nedkelly
08-06-2007, 07:09
The isolater protects you from power surges ie if a green box gets hit by lighting then this will go pop and protect your equipment and vice versa if you got hit it would stop there and not travel to the cabinet :):)
on in an hour!
08-06-2007, 08:48
The isolater protects you from power surges ie if a green box gets hit by lighting then this will go pop and protect your equipment and vice versa if you got hit it would stop there and not travel to the cabinet :):)
ned is dead right,you need the isolator,think of it as a type of fuse and youll get why its there.if you have scart feeds from the set top to dvd/vcr/tv then make sure your aerial isnt in your set top as if lightning hits your roof aerial the isolator is no use.;)
The main purpose of the isolator is to prevent dangerous voltages feeding back up the network and electrocuting engineers working on the system, or damaging equipment.
Normally this should not happen, but if there was a fault in your STB or if someone has messed with the wiring inside the house (an illegal install for example) then there is the possibility of mains voltage getting back up the network.
Do not remove this device!!!
as people have said,isolators are to protect surges of a certain degree in either direction,but lets face it if anything take a direct hit from lightening then theres not much you can do to prevent substantial damage being sustained.
sprattgraham
13-07-2007, 00:23
The isolater protects you from power surges ie if a green box gets hit by lighting then this will go pop and protect your equipment and vice versa if you got hit it would stop there and not travel to the cabinet :):)
They didn't install any here.
Cable comes from the CAB into a 3 way spliter, then goes into the rooms
Graham M
13-07-2007, 07:38
It would be very unusual not to have one, might be in the box outside.
sprattgraham
13-07-2007, 09:19
When we had the TV installed he removed the isolator and replaced it with a three way spliter
We have twp drop cables going to the omnibox out the front of the house, we of the drop cables isn’t used the other has a three way spliter one output runs to the living room another to another room then the third runs to a secound omnibox where there’s a two way splitter for the Broadband and another TV in the bedroom.
I can't be bothered to find the regs but I'm pretty certain that it is illegal to install cable TV without including an isolator. This has more to do with wiring faults than lightening protection. Adjacent houses are usually wired to different phases of the mains. Although there is only 230VAC within each house there is 400VAC between them. Normally, this is not a problem. But if there is a conductor between houses and a wiring fault within one of them, you may see 400V in the other. To avoid this lethal hazzard, any wiring that runs between houses has to include an isolator.
Your 3-way splitter probably has an isolator too:
http://www.technetix.com/productlist.asp?id=23&sid=34
It sounds to me as thpugh you have a TV/FM Diplexer that is used to feed TV signals and FM signals down the same co-ax.
See Maplins, is this what you have?
http://www.maplin.co.uk/module.aspx?ModuleNo=5126&doy=13m7
It is ok to remove this box if it is no longer required, i.e nothing connected to it.
The line should aslo be removed from the system.
You should ensure that where your equipment is now connected, it is via an isolator.
The general rule is this: Each bit of equipment should be connected to the line via an isolator such as VQ601LC. Example, From the line comming in (brown box outside) you have the line split 2 ways VQ1002 each line then goes to a single isolator then to STB or modem. You can see here that not only do you have protection from house to cabinet, but also between each bit of kit in house.
From what i have been reading more recently it is clear that since the change to virgin, many installers are not following these guidelines.
As an example, earlier this year Virgin dropped the use of the useful VQ302LC 2 way splitter/isolator (used where 2 bits of kit connected in same room, STB and modem).
They said they would instead use a sperate 2 way splitter and 2 single isolators VQ601.
Total maddness as this more expensive and very messy. More importantly, What is happening in many cases, is that a 2 way splitter is connected from a single isolator and then to STB and modem. Hence no isolation between the two.
---------- Post added at 13:58 ---------- Previous post was at 13:49 ----------
The VQ300 is a TV/FM diplexer/isolator now updated VQ330.
The likes of that shown in maplin link should not be used on virgin cable.
---------- Post added at 14:09 ---------- Previous post was at 13:58 ----------
They didn't install any here.
Cable comes from the CAB into a 3 way spliter, then goes into the rooms
If this splitter is green and has number VQ643 it is ok, combined splitter/iso.
If red and VQ1003, get them back to do job correctly.
sprattgraham
10-08-2007, 13:24
Just a small read one, I've had three techs out to look at the V+ and none of them have done anything about it.
Just a small read one, I've had three techs out to look at the V+ and none of them have done anything about it.
Just read your 2nd post again, if NTL/Virgin wired this then it is a major sloppy mess.
I am surprised you dont get problems. Isolators in situ correctly, also tend to reduce interference and hum. I have known a few instances where people have experienced interference on TV whilst their internet is being used, due to lack of correct isolation.
As said already, each bit of kit wired to the system should be via correct isolator.
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