All posts by Derek Green
Below are all of Derek Green's postings, with the most recent are at the bottom of the page.Solent-viewer,
Umm, I agree that's "sort of true". In a multi-element aerial side transmission reception is minimised by the director and reflector elements (over and above the main dipole element) whichever polarisation you choose. The horizontal wins which is why so many of our UK transmitters use horizontal to minimise side pick-up as we are such a small country. However, as we all know, mid-Southern England have particular problems with weather conditions and Northern France transmissions.
In essence, you have a choice of horizontal - with vertical reflections from layers in the atmosphere/troposphere, or vertical - with unwanted transmissions directly from the sides.
The advantage with the final state of Rowridge, post April 18, is that for the three "minor" commercial multiplexes the vertical transmission is 200kW, whereas the horizontal transmissions will be 50kW. On these multiplexes, this extra power in vertical polarisation must be better in our area! The engineers would not have designed it this way unless there is good reason.
For the other 3 "main" multiplexes they will have 200kW both vertically and horizontally, so it will make little difference which you choose.
And of course that at each unique location will need to try horizontal or vertical after April 18. If the aerial fittings allow, it might be that some might benefit from 45 degree or other polarisation somewhere between full vertical or horizontal polarisation? Just like the "mixed" polarisation for car aerial reception.
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Up until today (yes I have retuned today from factory resets!) I got good signal on most channels, even all the HD ones. This morning 08.40am all BBC TV and Radio channels are breaking up badly on two different Freeview devices. The same applies to most commercial channels. Odd. Is Rowridge at low transmitter power temporarily after final step? If so, hopefully they will boost up to full power.
Anyone else got problems?
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Geoff Smith,
Phew. At least one of you is having problems! It does make you go running around trying to fault find, probably pointlessly? I have rechecked all my connections but all 4 Freeview devices over the house are getting poorer signal strength this morning, certainly lots of digital breakups. I hope you are right about Rowridge having some problems! I am already on vertical polarisation and was getting good signal strength without the need any of the 3 boosters I had in circuit before 21 March. And virtually no digital breakups until this morning.
I am wondering whether it is co-channel interference yet again. I had hoped with the increase in power to 200kW on all vertical polarised multiplexes that this would be really minimised but perhaps not? I must go and have have look where the nearest high pressure zone is..... off to have a look on Met Office site!!!
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Geoff Smith,
I have just had the oddest experience. The signal strength was definitely down this morning, but I discovered that the 4 outlet distribution amp in my loft (which is over 15 years old!) had finally gone weird! The signal strength was 90% but the quality on all channels was varying wildly between 40 and 100%. I have just replaced it with a new one from B & Q (£14.99 for a complete aerial distribution kit with all sorts of cables, plugs etc that I did not need!!! but it was the cheapest option) and all the issues have gone away. There are still occasional digital glitches but very minor ones which I am assuming is due to the weather.... But I am back and running with 113 channels including all 4 HD ones.
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Monday 9 April 2012 6:15PM
Poole
Kim V,
You could try vertical polarisation of your aerial after the April 18 re-tune. This will involve getting your aerial elements rotated through 90 degrees. Before April 18 only a batch of the main BBC, ITV, Channel 4, Five etc channels, in three "multiplexes" but not the additional "minor" commercial channels, are being broadcast at 200kW on vertical polarisation. The remaining 3 multiplexes are still at a mere 20kW and horizontal polarisation only, but on April 18 they too will begin to be transmitted on vertical polarisation and at a massively increased 200kW too. With another re-tune and rotating your aerial, you should get all your missing channels back then and be less prone to co-channel interference from French stations.
Failing that, why not get a professional TV or aerial repair person in to sort you out, especially if you cannot sort it out yourself?