TV reception bad after fitting variable gain amp/splitter

[pls1]

A few months back I installed a digital aerial on the roof which was connected to a freeview box on the ground floor. Reception was perfect as the aerial has good line of sight from the roof.
I needed a second connection to an analogue TV in the bedroom so ran another cable to it from the aerial and temporarily connected it to the same screw connections on the aerial. Again reception was perfect for both the analogue and digital TV - all channels.
Recently I needed a third connection so decided to do it properly and fit a masthead splitter with a variable gain amplifier (which can be connected to one of the downleads in the house).
http://www.screwfix.com/app/sfd/cat/pro.jsp?id=26562&ts=40380
I went this route as i didn't know what strength the signal was and I would be able to vary the gain if necessary.
Now that three cables are connected, the reception is poor on all connections, varying the gain on the amp doesn't help. The analogue signal is grainy and the digital set isn't picking up half the channels it used to.
Am I not getting enough gain ? How can I rectify this?

 

[breezer]

remove the signal amp and see what happens

 

[pls1]

signal is even worse, digital TV has no channels and analogue TV a lot grainier

 

[Space cat]

Let's clarify this. You broke into the cable up at the aerial and put the amplifier in, aerial to input and the three downleads to outputs. (How many outputs does it have?) You also broke into one of the three downleads in the house and put the power supply box in, downlead to input and TV to output - and plugged it in!. After you'd done all this your signals on all three cables were much worse than expected AND the gain control had no effect.

Following breezer's advice, you removed the amplifier and everything got even worse.

Did you also remove the power supply? How did you link up the cable ends that you removed from the boxes? In particular, how are you splitting the aerial into three cables without using the amplifier?

 

[aptsys]

I'd first check that the screen hasn't come into contact with the centre conductor at any of the connections. This would lead to loss of signal.

 

[pls1]

So here's what I found out,
removing the masthead 4-way splitter and temporarily joining the aerial output to one of the downleads resulted in a perfect signal.
Putting the masthead amp back in again degraded the signal a lot and it didn't make any difference the gain setting on the amp or positioned it on any of the downleads.
I tried another 4-way splitter I had instead of the masthead splitter and this worked perfectly even splitting 4-ways without any amp connected!
Looking at the replacement splitter it is a Maxview 5-2300Mhz 4 way splitter. The masthead one which didn't work was a Labgear UHF 470-862Mhz.
Is the problem because the labgear splitter has the wrong frequency range? It didn't mention anything in the documentation.

 

[Space cat]

Freeview uses frequencies within the analogue TV UHF band so the Labgear does cover it. (In case you're interested, all the digital channels are multiplexed onto just six actual UHF channels.) Does the Maxview use the same arrangemant of a separate power supply and, if so, is it in the same place as you had the Labgear one?

 

[aptsys]

Was your power supply definitely connected to one of the downleads properly? (and working?)

 

[bernardgreen]

It is possible that the amplifier input is being overloaded by the signal from the aerial. When this happens the signal is distorted as is passes through the amplifier

If the signal from the aerial is strong enough to be split 4 ways with good quality pictures then it is quite likely the ampifier is being over loaded and either no amplifier is necessary or the input signal has to be reduced ( attenuated ) to a level that doe not overload the amplifier.

 

[pls1]

If the signal from the aerial is strong enough to be split 4 ways with good quality pictures then it is quite likely the ampifier is being over loaded and either no amplifier is necessary or the input signal has to be reduced ( attenuated ) to a level that doe not overload the amplifier.

I should of pointed out that the Maxview 4 way splitter I replaced the labgear with doesn't need an amp - the signal is strong enough. What I couldn't understand is that using the Labgear, even without the amp the signal was crap

 

[RF Lighting]

Does the labgear splitter / amp require a 12V power supply to make it work properly?

 

[Space cat]

I should of pointed out that the Maxview 4 way splitter I replaced the labgear with doesn't need an amp

When you say "amp" I think you mean the bit you put into an aerial lead and plug into the wall. That's not an amplifier, it's a power supply. It put low voltage DC onto the aerial lead to power the real amplifier which is up by the aerial.

Since the Maxview doesn't need one it must be a passive splitter; it just divides the signal from the aerial between its four outlets. Each one will receive a weaker signal than it would have done directly from the aerial but this can be enough. I have TVs working quite happily on an aerial signal that's been halved three times in splitters. It's 18dB down but still adequate.

The Labgear really is an amplifier so it can put out a stronger signal than it gets from the aerial but --- IT NEEDS POWER! It's possible that when you tried to use the Labgear there was something blocking the flow of DC from its power supply. Some TV outlets have internal capacitors that block DC. Without power, not only will your Labgear not amplify; you'll be lucky to get any signal through it at all.