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Picture break up on Aura
- Thread starter MikeSh
- Start date
OP
MikeSh
Well-Known Member
Shouldn't be. Rowridge is unusual among main transmitters in having both H & V polarities with, AIUI, the latter being to help avoid interference from French transmitters, which presumably are H. They are the only TV transmitters in that direction.
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Black Hole
May contain traces of nut
In as much as the main transmitters are H, but I believe the lobes are wider in H than V (for a V antenna).
Don't know, just asking the question.
OP
MikeSh
Well-Known Member
I saw something that suggested that for a horizontal aerial the acceptance angle was narrower in the lateral plane than the vertical. So that would suggest that if turned vertical it would have a wider lateral acceptance angle ... which ought to make it more susceptible to catching other signals.
Of course it didn't say how much difference, so it may not be enough to matter in reality.
peterworks
Ye Olde Bowler
Don't know if it helps but I am on the East side of the Isle of Wight. I have a wideband aerial in the loft (vertically orientated) which looks like the attachment. I have no line of sight to Rowridge and plenty of Oak trees in the path plus a hill.
My reception is perfect (except for Sky Arts which does break up on the very odd occassion) and it feeds two Humaxes plus the TV.
It looks something like this.
My reception is perfect (except for Sky Arts which does break up on the very odd occassion) and it feeds two Humaxes plus the TV.
It looks something like this.
OP
MikeSh
Well-Known Member
Interesting. That's the mux (22) that was worst during my brief test in V. On both the Aura and the FOX it had less signal power displayed than in H, despite V being advertised as 200kW and H only 50. I put it down to my poor aerial mounting but maybe there is actually. something strange with it.
Black Hole
May contain traces of nut
Maybe; it was just my hunch but RF isn't my thing.
Do you have an amplifier?
Rowridge Vp was Planned by UK Spectrum planners to protect from co-channel Continental transmitters using Hp. They expected new aerial install/replacement in the areas served to use Vp rather than Hp (and eventually not need Hp transmit). Then Arqiva did the COM7/8 thing. 
How was the aerial changed to Vp?
A) Taken off the cradle and refitted? so the cradle and pole was in-between the directors?
B) Taken off the pole and the cradle to pole fixing adjusted to Vp, so there's a sideways load on the pole and fixings?
Either way the pole and other metalwork could well have frequency dependent interactions. More so than in Hp orientation.
Non line-of-sight signals can include diffractions and reflections off things and may need the aerial to be moved in a cube of space with roughly 1 metre sides up/down crab left/right and fore/aft to find the sweet spot where all wanted signals are roughly equal. A pro installer uses a spectrum analyser display to aid this process. Even tilting the aerial up to the sky a degree or two can make a difference.
DIY installers have to use sight of receiver signal meters and check all frequencies after every aerial position move.
It's all to do with wavelength, path lengths of direct vs reflected, selective absorption (tree leaf size) etc,. giving cancellation and/or reinforcement.
https://www.aerialsandtv.com/knowledge/aerials/aerial-polar-response-diagrams has some plots of a sample real receiving aerial at ch 21 Vp and Hp. Not very signficant differences to the front. Rear/side lobes however are different.
i
How was the aerial changed to Vp?
A) Taken off the cradle and refitted? so the cradle and pole was in-between the directors?
B) Taken off the pole and the cradle to pole fixing adjusted to Vp, so there's a sideways load on the pole and fixings?
Either way the pole and other metalwork could well have frequency dependent interactions. More so than in Hp orientation.
Non line-of-sight signals can include diffractions and reflections off things and may need the aerial to be moved in a cube of space with roughly 1 metre sides up/down crab left/right and fore/aft to find the sweet spot where all wanted signals are roughly equal. A pro installer uses a spectrum analyser display to aid this process. Even tilting the aerial up to the sky a degree or two can make a difference.
DIY installers have to use sight of receiver signal meters and check all frequencies after every aerial position move.
It's all to do with wavelength, path lengths of direct vs reflected, selective absorption (tree leaf size) etc,. giving cancellation and/or reinforcement.
https://www.aerialsandtv.com/knowledge/aerials/aerial-polar-response-diagrams has some plots of a sample real receiving aerial at ch 21 Vp and Hp. Not very signficant differences to the front. Rear/side lobes however are different.
i
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OP
MikeSh
Well-Known Member
A, which was wrong. I thought it was it when doing it but only after restoring it to H did I sit down and research a bit. In fact I actually found the paper instructions that came with it which specifically said not to do what I did. Doh!
OP
MikeSh
Well-Known Member
Out of curiosity this morning I checked the signal strength of 25, the weakest mux. It was 82 from my previous check and it was more or less the same today but bouncing all the time between 78 and 86, very occasionally it hit 90. It's pretty windy today so I'll hypothesize that it's because the trees are waving around so much.
Also odd was that the reading seemed to be in steps of 4 - it only read 78, 82, 86 and 90. I'm pretty sure I've seen better resolution than that before (on other muxes probably). Maybe the rapidity of changes means it can't average fast enough.
Also odd was that the reading seemed to be in steps of 4 - it only read 78, 82, 86 and 90. I'm pretty sure I've seen better resolution than that before (on other muxes probably). Maybe the rapidity of changes means it can't average fast enough.
peterworks
Ye Olde Bowler
Sorry for the late reply - been away for the weekend. No I do not have an amplifier.
The aerial was fitted by a pro with all the, I assume, right gear.
To reiterate Sky Arts only breaks up on very rare occassions.
Black Hole
May contain traces of nut
peterworks
Ye Olde Bowler
'Experts' - they have a very good reputation on the island
We had our aerial fitted by a 'Pro' when we moved into our new house 5 years ago, but we couldnt get all the HD channels. We were told that's as good as its going to get.
Went across and looked in my neigbours loft and noticed their aerial was aligned vertical and much bigger, so I went out and purchased a bigger aerial to replace the pathetic one he supplied and aligned it vertical and using an app on my phone I then received all the HD channels plus a lot more!
Went across and looked in my neigbours loft and noticed their aerial was aligned vertical and much bigger, so I went out and purchased a bigger aerial to replace the pathetic one he supplied and aligned it vertical and using an app on my phone I then received all the HD channels plus a lot more!
Black Hole
May contain traces of nut
I put up aerials for a friend about 30 years ago, H to Mendip and V to Mynydd Machen (thus avoiding crosstalk), only for another friend to decide that was wrong and realign the Machen aerial to Wenvoe!
Black Hole
May contain traces of nut
I don't recall.
OP
MikeSh
Well-Known Member
It's been a while since they appeared to have finished messing with Rowridge and saying there might be picture breakup, and since then SWMBO says she hasn't had any. So I think that was almost certainly the problem.
Out of curiosity I'd like to try it in V (next door has had a new aerial installed and that's been set vertical) but the location makes it a physically demanding job and not without risk, so I'll leave it all as is unless/until something goes pooh again.
Interesting discussion though and I have learned some stuff.
Out of curiosity I'd like to try it in V (next door has had a new aerial installed and that's been set vertical) but the location makes it a physically demanding job and not without risk, so I'll leave it all as is unless/until something goes pooh again.
Interesting discussion though and I have learned some stuff.