Right, strange "reception" problems with FV relating to a twin wallplate diplexer....

[Matt_C]

Okay, odd one this, can't figure it out...

Couple years ago got my mum two freeview boxes for the two TV's she has. Aerial on roof, one cable comes down side of house, and goes through hole in wall to a TV point. On this is a twin output diplexer thingy. One cox runs to one TV, one runs to TV in other room (both run under floorboards)

So, when we got them they worked fine, virtually no probs, everything cool.

Lately, she's been having problems specifically in the "other" room (other being the room where there is no direct RF output, cable runs from diplexer wall plate in "room 1" under floorboards directly into back of FV box). This I could solve by swapping cables over from output A (other room) to output B (room 1), but of course this meant that output B wasn't providing signal to tv in room 1, so not a great fix. Sometimes I swapped em both over (now output A is feeding tv in room 1, and output B is feeding TV in other room) This would work for a while, end up swapping back again.....

Anyway, decided first thing to do was replace the diplexer. Got new one, removed old one, fitted new one, worked fine. Happy days.

Now it is back to it's old tricks!!!

The problem is that FV reception on other room keeps losing signal, very eratic, but only with specific mux's (whatever mux ITV2 is on) and signal jumps constantly from low to high, meaning a breaking up and very blocky picture.

Now, I made a discovery this eve on a fleeting visit : output A is feeding FV in other room, output B is feeding FV in room 1. If I unplug output B, FV in other room instantly becomes perfect - even tho I haven't touched that cable! Soon as I plug output B back in, reception in other room goes pants again. Doing the opposite has no effect on reception in room 1, as this is either perfect, when plugged in, or non-existent, when unplugged.

I don't get it? I don't understand how the diplexer would be giving some sort of intereference(sp) between the two? I realise it's not isolated as both outputs share a common input, but for this to happen with two dixplexers?

Perplexed, I am!

Would I be better trying a) yet another diplexer or b) fitting an external RF splitter (like this : PICCY LINKY) outside and feeding two coax's into the house, to an isolated twin output wall plate?

Any idea's?

 

[J7MAN]

Are you able to get upto the rig? A twin output masthead amp would be better than a splitter.

 

[njp]

Just replace the passive splitter (a diplexer is a different beast entirely) with a simple amplified one. That should avoid the adverse interaction between the two sets. I suspect the problems only manifest when the signal strength drops for some other reason - you clearly don't have much margin to play with!

Like the man said, a masthead amp would be best, but it's more effort, and the history suggests you don't need it.

 

[Matt_C]

It doesn't have a passive splitter - one cable goes into the back of the wallplate which makes it into two outputs...

Can't get up to the aerial at all, and not found an aerial installer who has the guts to get up on our roof (its fapping high!!!!!!)

Don't get why it worked for ages, then don't. replace diplexer, worked, now don't again!


I hope I am not using incorrect terminology; I was led to belive that a wall plate that has one in and two out is a diplexer! It's not a TV + FM seperator or anything just a simple one of these;

One cable goes in the back, and both outputs work, lol.. Well, at least they DID work.... Now not so much lol

 

[J7MAN]

How highs your roof Matt?

 

[Matt_C]

no idea

high enough that we have never had a window cleaner brave enough to do the upper storey windows! Needs re-slating but anyone who has ever come round for the quote has taken one look and said "no chance" and done a runner LOL

 

[mrfreeview]

It doesn't have a passive splitter - one cable goes into the back of the wallplate which makes it into two outputs...

Can't get up to the aerial at all, and not found an aerial installer who has the guts to get up on our roof (its fapping high!!!!!!)

Don't get why it worked for ages, then don't. replace diplexer, worked, now don't again!


I hope I am not using incorrect terminology; I was led to belive that a wall plate that has one in and two out is a diplexer! It's not a TV + FM seperator or anything just a simple one of these;

One cable goes in the back, and both outputs work, lol.. Well, at least they DID work.... Now not so much lol

If you look at this twin BellingLee socket on the backside then you should find that in each of the connections from the terminating stud of the coax there is a resistor in series to each of the sockets on the front. This is attempting to create an impedance match for the connection of two devices. The output signal stregnth from each of the sockets will only ever be, at best, 1/2 (3dB less) of what is available at the end of the coaxial cable on the back side of the sockets.

It could verywell be that your DVB-T Signal Strength is so low that when you have a fade margin problem the signal becomes so low that the STB decoder can't decode the signal. (The minimum received signal strength of a DVB-T signal should allow, as a mimimum, for 6dB of fade margin.)

If you have a signal strength meter on your STBs even if it is only displaying as a percentage - have a look and see what level you have. This will give you a clue of what you can do to improve things.

You may find that you can get away with replacing the current dual socket face plate with a single socket so as to get access to the full signal strength (you will never do this by using just 1 of the sockets!) and then add a small 2 output amplifier.

I hope my post has been of use

 

[Matt_C]

STB has signal strength indicator - on all channels it is usually abover 3/4's, cept on tv in other room on ITV2 mux channels, unless you pull the other output out...

 

[mrfreeview]

STB has signal strength indicator - on all channels it is usually abover 3/4's, cept on tv in other room on ITV2 mux channels, unless you pull the other output out...

Sorry all this room 1 and ""other room" is getting a bit confusing!

If I am reading the post correctly:

You have a cable from Coaxial socket "B" to a STB/decoder in room 1

&

You have a cable from the Coaxial Socket "A" to a STB/Decoder to Room 2

So you have cables as: A->Rm2 & B->Rm1

Again if I am reading correctly: If you disconnect the cable that goes to Room 1 STB at socket B, then the STB in Room 2 connected at Socket A works correctly.

If this is so then try reversing the A & B so that "A" goes to room 1 and "B" goes to room 2. (so you now have A->Rm1 & B->Rm2)

What is the impact then?

Does the decoder in Room 2 again stop working correctly? And if what happens if you now disconnect the cable to room 1 (in socket A) does the STB in room 2 then work correctly?

If so then I think the fault is either on the cable to room 1 or its STB

Does the STB in Room 1 have an RF modulator? If so is it turned on? and if so to what channel? Is it set to the channel used for the ITV MUX?