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All posts by John

Below are all of John's postings, with the most recent are at the bottom of the page.


I am getting very variable signal strength on the BBC multiplex at 7:45 tonight watching the England-Wales rugby programme. Normally the quality is rock steady at 100% but while it is at 100% mostly, it is dropping to 30% or 40% for a second every now and then. Strength is 58 to 60%.
Strangely, all the other multiplexes, including the low power ones, are absolutely fine, with rock steady 100% quality (eg ITV is 62% strength, 100% quality).
It is very windy but I have checked and my aerial is not moving in the wind.
Does anyone have any ideas?

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GB

Briantist
Thanks for you reply "There is a weather front moving over the UK causing tropospheric ducting ... "

I thought it must be something like that - and you have stopped me from trying to fix summat wot ain't broke!

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GB

The BBC multiplex (62) on Mendip has suddenly started breaking up for me, and judging by the variations in signal strength and signal qality mI am seeing, it is co-channel interference from a distant station.

Can anyone help by pointing me to a schedule which lists the dates of each of the changeovers and the channels on which the main transmitters transmit? I could then track down what might be the intefering station.

I could do it the long way (enterring postcodes appropriate to each main transmitter in the postcode checker) but I would have expected there was a listing somewhere.

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GB

Sorry for the typo.
"The BBC multiplex (62) on Mendip" should of course be "The BBC multiplex (61) on Mendip"

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GB

I have discovered your link Transmitters has Find Freeview by frequency, and when I enter 61, I get shown all the transmitters transmitting on 61, and their (planned? actual?) changeopver dates.

The Workington relay in Scotland started transmitting its BBC multiplex on C61 on 22 July 2011, so it could be a candidate for causing the inteference with my Mendip signal.

But it broadcasts on only 10Watts. Is it feasible that a 10W signal from Scotland could cause co-channel inteference with a 100kWatt signal from Mendip? I normally receive Mendip 61 at 60% strength and 100% quality but I am now seeing it drop to as low as 40% strength and 10% quality.
All other Mendip multiplexes are OK so it is unlikely it is my aerial etc.

There is no transmitter work reported on Mendip.

Any thoughts will be appreciated!

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Briantist
Thank you. I am bee ess fourty seven tee are and the initials are aich oh.
I called the Digital TV Help Line and they gave me the number for the Trade help line and neither could offer anything other than no problems are reported at Mendip and thererfore it's not the signal. They blame my arial/box and suggest I re-tune the receiver.
Neither of these account for why the ITV mplex 54 is still at 60% and working OK.
I retuned the box but it made no difference. My other box shows the same problem. The aerial looks fine. I have no amplification. I am an electronic engineer with ham radio experience.

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GB

Briantist
One more thing - in March 2011 the Trade View of the postcode checker said the BBC mplex C61 and the ITV mplex 54 coverage were 96/98% and 99/99% respectively for me. It now reports them as 84/89% and 87/92% respectively.

Have you any idea why they have reduced?

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GB

Briantist

> There is a list of the switchover order ...

Thank you - that is a very useful site and just what I was looking for!
Nothing in the weeks before 27 July (in case it was delayed) or the weeks after (in case it was brought forward) seems relevant. The closest is Sudbury (London) upped the power of ArqA on Ch 60 to 100kW on 20 July, but I cannot see that being a problem with Mendip Ch 61. The other Sudbury mplex are on 41, 47, 56 and 58 so again no problem.

My line of sight to Cork is across water - do you think I could be getting Irish (or continental?) co-channel inteference?

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GB