electrical interference and saorview

pegasuspub

house with 3 tv's,one with saorview built in,and 2 analogue only all fed from attic where there is a vhf antenna for rte and a uhf grid antenna for tv3,tg4 and saorview combined with triax vhf/uhf masthead amplifier(screened type).house in countryside and good analogue reception,normal saorview reception excellent....... now the problem... saorview reception breaks up due to electrical interference caused when the owners laptop,washing machine,kenwood mixer,hoover is operating.....to try and solve the problem i did the following...
1.i changed the plastic ross splitter in the attic for a triax metal f type.
2.i changed the downleads for heavier double screened types.
both of these did not solve the problem
3.i changed the mast head amp
4.i disconnected the vhf antenna
5 i changed the grid antenna for a folded dipole yagi grouped type
6.i tried to earth the outer screen of the coax to the electrical earth
7.finally as a last resort i ran a separate coax lead from an outside chimney directly to the saorview tv(no amp,no joints)
all these options failed,the picture still broke up when some of the appliances were on,although not as bad,but still bad enough to annoy viewing,in the end after 2hrs i reconnected all the old gear and left it as it was originally.... what am i missing here?how are the electrical impulses getting into the system?i thought moving the aerial outside and as far as possible away and without an amplifier would have solved it.....what a waste of a morning any advice please.

watty

Indoor aerials, just as much in attic are notorious for interference pickup. That's why even in a good reception area a small 10 element or 4 x bow tie grid at least 1m above the roof ridge (and more if nearby house on Transmitter path is on higher ground).

There is no substitute for an outdoor aerial. On the face of it that is the solution. So when you tried an outdoor aerial did it have a "balun" built in? What type of coax and how "good" was the Analogue reception with it?

Note Analogue reception is only "good" if there is no "snow" at all on TG4 and no mast amp is needed.
A mast amp is only to counter loss of the down lead cable (or possibly the loss of a 4 way passive splitter, 6dB to 8dB), so too much gain makes the system vulnerable to overload and thus disruption from interference.

channelsurfer2

thats interesting watty. As an observation on that point, mine is installed on the gable end just about 1 metre above the gutters but not about the highest roof level point as its a timber framed house with no chimney. I did notice last week during the rain that the signal was lost and checked. seemed the signal strenght had gone down to 39% and quality 1%. now today it is 30-35% and 100% quality when i upped the gain on the amp. It used to give readings of 55-58% signal.. I thought 40% was the min needed for DTT signal? ( i think its because of the ordinary rg6 cable i used instead of WF100 cable or similiar and the Triax aerial which I would not recommend using http://www.triax.co.uk/Products/Aerials/UHF%20Aerials/Supergain%20-%20Yagi%20Aerials.aspx?productId={36D81A39-9DF4-4E6B-9B84-B143B8D2EDE0}&Tab=0 as the rain plays havoc with it.

Peter Rhea

Rain doesn't 'play havoc' with aerials, you must have a poorly waterproofed connection somewhere.

There's nothing wrong with those Triax aerials.

channelsurfer2

have to disagree with you there. all the connections are dry. the masthead amp is dry. I even got up in the pouring rain and checked. the aerial itself retains the water on it to no ends and you can see it very obviously. when the aerial is dry the signal quality improves.... and before you ask the coaxial cable is dry at every point.anyway i dont want to detract from the thread. it was just my observation...

Peter Rhea

I remember reading this thread about the effects of rain & yes, the effect of rainwater gathering on the aerial is referred to but I've never known it to have such a dramatic effect.

Sam Russell

Interference is best dealt with at source. Check that the earth connections on the equipment causing the problem. Check that supressors are installed. I would work on the source first. (It is nearer the ground).

Booms

Pegasuspub:
What's you signal and quality strength as reported by the tv? (should be accessible in the menu)

whizbang

If you can vary the gain of the amp: start at lowest setting and step up in small stages. record signal level and quality for each step in gain (saorview only), post results back here.
Are you sure its saorview only? its very easy to ignore noise on an analog tv.
have you tried moving TV to different room?

Peter Rhea

@ the last 2 posters: I suspect the OP here is an installer.

pegasuspub

correct peter,i was called to check the problem,i did not install the system first day and assume the masthead amplifier was used as the signal is split in the attic where all the cables are and as there was no mains socket and just a lighting supply it is dc fed from a 12 volt psu behind one of the tv's via a power pass port on the triax splitter.the last antenna i tested was a triax 18a and the dtt signal was at 49dbuV with a signal to noise ratio of >40db,this is from mullaghanish on channel 21 and is the only dtt transmitter available at the site.the triax 18a was the best antenna i had in the van at that time,i have not returned to the site since as i was hopeing for inspiration.obviusly the interference is visible on the two analogue tv's also but it totally wipes out the dtt signal and two of the interference sources do not have an earth wire as most modern domestic appliances[hoover etc ] are double insulated i believe ,the last cable i tried was tx100 and i used this to feed the dtt aerial only on a back chimney and directly to the newer tv,without any amp and without any joints,as this didnt solve the problem i was slow to move all the antennas,i have to keep analogue going for the moment because of the two older tv's.if i thought moving all antennas outside as far away as possible from the interference source i would do it,but if it fails i certainly wont get paid for it,any thoughts from learned boards users appreciated.

watty

Check there isn't a loose wire in the Fuse box.

whizbang

change the power supply?

Johnboy1951

If the interference is coming along the power line then try powering the devices for TV reception from a different mains line from the fuse box ....... and maybe even try a mains filter in the line feeding the devices.
A quick test might be to power the devices from a filtering UPS to see if there would be any improvement.