[maxlemon]

Anyone experiencing problems with BBC from Rowridge? I'm in Gosport area and the picture seems jumpy. Had my aerial turned for vertical polarisation reception. There was no particular need for this, I just saw it was a higher signal and automatically thought it would be better (for the Mux's where vertical was higher). Probably unnecessary?

Whilst I typed this I thought of turning the (loft) aerial for horizontal polarisation. Seems fine now, no stuttering.

So my question is now why would vertical polarisation be suffering at the moment? It's a bit academic as all is fine on horizontal but I'm interested now.

Any ideas?

[brumlad36]

Originally Posted by maxlemon

Anyone experiencing problems with BBC from Rowridge? I'm in Gosport area and the picture seems jumpy. Had my aerial turned for vertical polarisation reception. There was no particular need for this, I just saw it was a higher signal and automatically thought it would be better (for the Mux's where vertical was higher). Probably unnecessary?

Whilst I typed this I thought of turning the (loft) aerial for horizontal polarisation. Seems fine now, no stuttering.

So my question is now why would vertical polarisation be suffering at the moment? It's a bit academic as all is fine on horizontal but I'm interested now.

Any ideas?

It may be that your system is suffering from overloading. All six Multiplexes (MUXs) transmit 200kW on vertical polarization, whereas only 3 MUXs transmit 200kW on horizontal polarization. The other 3, commercial (COM) MUXs, transmit 50kW on horizontal polarization.
So you may be getting too much overall signal with your aerial vertical (6 x 200kW, instead of 3 x 200kW + 3 x 50kW).

Chris.

[SimonBlackham]

I switched to vertical immediately after DSO - and then changed back to horizontal on a different aerial because of reception problems.

I have not got back to it yet as I have Freesat as a backup (and I have been setting up 19.2 satellite for free F1) - but I intend to switch to vertical on a re-positioned aerial when I have time as this should be better at eliminating French interference. (we used to use Mendip which also eliminated French interference).

[SimonBlackham]

Reception has been terrible over the last few weeks...

I have both H and V aerials and vertical is far worse.

The channels giving poor and often no reception are HD and channel 28 - particularly from around midnight to 8am.
I suspect that 28 is getting co-reception from Stockland Hill during the good weather - but how on VP???
HD on 21 is very flaky.

It was never this bad before DSO.


I am going to review and re-install from scratch when I have time.

PS H and P give characteristically similar poor reception - there appears to be little difference between the reception levels and quality between them even with the COM MUXes.

[Mark C]

Originally Posted by SimonBlackham

Reception has been terrible over the last few weeks...

I have both H and V aerials and vertical is far worse.

The channels giving poor and often no reception are HD and channel 28 - particularly from around midnight to 8am.
I suspect that 28 is getting co-reception from Stockland Hill during the good weather - but how on VP???
HD on 21 is very flaky.

It was never this bad before DSO.


I am going to review and re-install from scratch when I have time.

PS H and P give characteristically similar poor reception - there appears to be little difference between the reception levels and quality between them even with the COM MUXes.

This morning there's a huge lift on I think. All muxes from Hannington were unwatchable for me, I suspect CCI from Sutton Coldfield, which for me is on the same bearing.

Forget the TV, and get out there and enjoy the sunshine is my advice !!

[tr_ramsgate]

I am not at all surprised that there should be reports of poor reception in high lift conditions after DSO.

Transmitters which would never have come in on the pre-DSO power now have the potential to interfere even if the nearest transmitter has increased power.

And, of course, there a fewer channels in the spectrum to allocate, and relays have gone digital to add to the problem of co-channelling.

In the South of England the situation is further exacerbated by French transmitters having also increased power at around the same time as the UK DSO - although their DSO preceded ours in the South, many transmitters remained on low power until we moved around our frequencies..

Here in Ramsgate (20 miles from Dover) the massive extra power at Dover does not guarantee the absence of interference from Continental transmitters even when they might be at a considerable distance.

I could well imagine that the most reliable performance can come from re-orientating the aerial for maximum exclusion of the potentially co-channelling transmitter rather than on-beam orientation to maximise signal strengh of the desired reception.

An aerial that was capable of pulling in the previous low powers will deliver more than enough signal strength in off-beam positions.

I have certainly experienced the reception of V-polarised signals from my local relay with an H-oriented aerial.


.

[Analogue110]

I'm sure lots of problems are down to aerial systems designed for pre-DSO conditions. Have a read of this from 1969

http://www.bbc.co.uk/rd/publications..._1969_20.shtml

[David (2)]

Living in a overlap between main & relay i can also confirm that reception of V signals is poss on a H pol aerial and vise versa. Clearly this needs more signal to work but it Does.

Should add that you dont need to pick up much signal in order for it to register with the decoder, although this is far too unstable to use as your main station. Eg modest wide-band aerial V pol (no amp) for relay picks up a few chs from main mast in our street, even though pointing 90deg wrong way-which is why when we switched i insisted on a Grp aerial for the relay-isolation is perfect on this-and isolation is critical in my view

[maxlemon]

Thanks for the replies. For me it was only ever the BBC channels being a problem, but since going back to horizontal all has been fine. And it stopped the moment I moved the aerial. But I expected interference on horizontal not vertical hence my original post.

The digital signal here always has been really good, just a (10 year old "modern" aerial) stood on a beer crate in the corner of the loft and pointed south-west.

[albertd]

Originally Posted by maxlemon

The digital signal here always has been really good, just a (10 year old "modern" aerial) stood on a beer crate in the corner of the loft and pointed south-west.

If Rowridge is SW of you, that means that the transmitter near Rennes in Brittany is over the horizon beyond Rowridge with an 80kW Mux on Ch 24 (the same channel as BBC for you). That could be the cause of a problem in a lift.

There is another at Rouen, but that should off the side of your aerial.

[maxlemon]

Originally Posted by albertd

If Rowridge is SW of you, that means that the transmitter near Rennes in Brittany is over the horizon beyond Rowridge with an 80kW Mux on Ch 24 (the same channel as BBC for you). That could be the cause of a problem in a lift.

There is another at Rouen, but that should off the side of your aerial.

Rennes in almost due south, probably SSW but that kind of thing is interesting to know. Why would that only impact vertical signals though, I assume the Rennes is horizontal as most French seem to be but I cannot find specific data on Rennes.

Thanks though, I find this interesting but luckily all is well on horizontal polarisation.

[-ajm-]

I noticed some poor reception this morning. I assume its due to atmospherics, interference and such

[albertd]

Originally Posted by maxlemon

Rennes in almost due south, probably SSW but that kind of thing is interesting to know. Why would that only impact vertical signals though, I assume the Rennes is horizontal as most French seem to be but I cannot find specific data on Rennes.

Thanks though, I find this interesting but luckily all is well on horizontal polarisation.

Yes, Rennes is horizontal, but you can get some strange things happening with propagation over a long distance.

[SimonBlackham]

I would still expect that the COM MUXes on Vertical would be better because of the hight power and the different polarization.

I am using a log period on vertical so would also expect a better rejection of horizontal c/f an X element extragain (which I am using for horizontal).

I thought it may be over amplification (and therefore clipping) - but I cannot find anything greater than about 80% signal (on the BTvision box).

The log-periodic is amplifier is on the masthead and does not work when off - so I cannot easily test with no amplification (I will move its amplifier into the attic so I can "switch" it in and out).