Selecting good frequencies for analogue transfer.

27 Jan 2008
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Llanfair Caereinion, Nr Welshpool
United Kingdom
I have ms with TV’s and a satellite dish with 4 outputs and two aerials feeding a mast head amplifier with two outputs.

Two outputs from dish and two from aerials feed the living room where we have a TV and an old Sky box plus a box with freeview + free to air box satellite and a USB input which I use to show pre-recorded films.

Two satellite outputs also go to my wife’s bedroom where it powers a sky+ box.

Mothers bedroom is supplied with a single coax from living room and at the moment it is connected to the old sky box in the living room but hardly used so not too worried about that.

The new living room has a shoot gun cable to old living room with a satellite plug on one and TV plug on the other, plus a second cable which goes to my wife’s bedroom with a inferred eye so we can control the sky+ box from new living room.

However the new living room has problems, the freeview pixulates and the sky+ has interference flashes that come across the screen, and the two satellite boxes from down stairs have a very poor analogue picture, just good enough to see what mother is watching but not good enough for watching our self.

Analogue signals on channel 21, 28, 36 at moment only 21 watchable.

I am sure a pre-amp can cure freeview but really want to watch sky so getting rid of the flash lines of interference is main aim, plus if possible improving the signal from the two satellite boxes down stairs.

When programming TV with freeview I noted some were NorthWest and some were marked Welsh so it would seem two aerials are pointed to Moel-y-parc and Winter Hill. I got Liverpool Bay which I will guess comes from a repeater as too weak to watch. We are living just where the river Dee starts to become an estuary in Shotton just 3 miles from English boarder.

So I seem to remember that the RF output from Satellite boxes is not very clean and my problem is likely due to channels selected for the analogue output to the Smart TV in the new living room.

Rather than sit there trying each channel in turn can some one suggest three channels which will not interfere with each other? The channel 38 degraded 21 so moved to 36 which seems OK, But channel 21 looks like some one is using a drill without suppressors, but it’s there all the time.

Cables all plastered into the wall so can’t really go for better cables.
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I wouldn't give up on the frequency changes just yet. Finding a better channel can take some perseverance. There have been times when I have looked and tried all of the unallocated frequency slots and then whittled it down the best 3 or 4. That's just with a single Sky box. You've got two boxes in your system, so you're juggling even more.

If it was me on site I'd start by simplifying the system. Start with the RF out from just one box along with your aerial feeds. List out all the unallocated channels and then go through methodically and test each one. You'll quickly build an overview of channels that are poor, ones that are good and ones in the middle. Add the second box (on a different frequency) and repeat the exercise.

There are some other unknowns (for us at least reading your posts from a distance) in your system. Are you using decent cable? I'm talking WF100 for anything carrying the TV aerial signals. This includes any fly leads from wall sockets and daisychaining any RF loop-throughs. How are your cables routed; do they travel parallel to any power leads/mains cable or near any poorly shielded power supplies?

Signal flashing and pixellation could just as easily be a sign of too much signal strength as too little. I wouldn't add any signal boosting until you're sure that too little power is the real culpret. Use the signal meter in the TV to check strength on one of the Freeview mux frequencies. If Strength (S) is 60% or higher then it's unlikely you need more power. Quality (Q) is the key. Ideally you want Q at 80-100% and S needs be no more than 80% or you risk over-saturating the TV tuners. You're receiving (I believe) from Moel-y-parc and from Winter Hill. These are two high-power transmitters, so unless you're in a very difficult location or there's some issue with your aerial and/or cabling then I'd be very careful about adding extra boost. All it does is compensate for power losses in cable and joints. It does nothing to improve quality (Q) which is the really important part of the signal.
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It seems something odd going on, as signal and quality change as we are watching, also seems every other day main box is asking for a re-tune. I will spend a little more time, but if can't find it soon I will kick freeview to touch, and use satellite only.

Seems channels 32, 34, 39, 42, 45, 48, 51, 52, 58 and 59 are in use, only 42 gives consistent good reception rest are up and down like yo-yo's.

I thought it was just my house in Bryn-y-baal which is high and gets Central, Welsh and Northern, but it seems even in Shotton there are still problems with freeview, I blamed the mast head amp power supply to start with, on turn on everything seems to work, but 2 hours latter is seems to fail, but swapped and still the same.

And no I am not transmitting, my 70 cm set has failed so could not transmit on TV channels even if I wanted to now.
As long as there's no 4G interfence in your area then try a frequency between 60 and 68 as a start.
NOT including 60 as it's too close to 59.

Frankly, there are so many possibilities for interference that your best bet is a competent technician with a spectrum analyser that can see what's there. Guessing is seldom successful.
Thanks, think you are right, think I will just use satellite and kick freeview to touch. Been in the house 3 weeks, it has requested re-tuning freeview around 10 times, no freeview aerial and then no co-channel interference so I will have to consider sky multi room and kiss good by to freeview.
But Freeview is free.

And Sky is no longer providing standard Sky+ Digiboxes. They have been dropped in favour of Sky-Q (which probably costs more.)

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