North West Wales mux 12D strange signal variations

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Andrew Webster,Wigan
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Joined: 18 Sep 2014 16:03
Location: Wigan Northwest England
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North West Wales mux 12D strange signal variations

Post by Andrew Webster,Wigan » 12 Oct 2016 20:12

When I first received this mux one thing caught my eye the signal level was up and down so monitored it and it still did it weather was settled at the time then when we got windy weather it still behaved the same so I thought why is the signal varying like this.

Image

This what it it does most of the time sometimes it can settle at one level but not more than about 10 mins then it's off again.
At first when I received this mux I had to beam West because of the Stoke mux also on 12 D so off beam then I discovered I could receive a better signal beaming N/E so Conwy coming off the back of the beam.
This first video I made shows the mux beaming West.

https://youtu.be/H6ApU0S_dok

The second video was last Sunday beaming N/E.

https://youtu.be/TYdlkfaUYZI

This is the path of the of the mux 79 km long is shown below

https://lh3.googleusercontent.com/-rzlC ... 050/64.jpg

None of the other muxes behave like this checked the Bradford mux similar distance but that's stable the Birmingham/Shropshire muxes do vary but nothing like this they move slowly.
Anyway a few pictures of the the signal varying.

Image

These two from this morning first 10:38 second 10:40.

Image

Image

The timescale of the graph is two mins the red line is the signal the blue line is the average.

So the burning question is why is this happening I was thinking is the an effect of the sea or is the path crossing the City of Liverpool or aircraft scatter the mux does act like the last two pictures every day and even when it was blowing a gale the other week.
So any answers welcome.

Andy
Receiving equipment: 2 Sony ST-S311, 1 Sony ST-SE520, 1 Sony ST-SE700 2 crossed FM 5s rotatable, 1 homemade FM 3 horizontal beaming S/E, 1 vertical FM 3 fixed beaming at Ireland, 2 element band 1.

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Julian Hardstone
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Re: North West Wales mux 12D strange signal variations

Post by Julian Hardstone » 13 Oct 2016 01:28

Excellent observations Andy. That's a strange effect, I could understand it on Ch. 10D because you would almost certainly be receiving the same mpx from 2 or 3 tx, St Johns in Liverpool (line of sight for you), Moel y Parc and Wrexham Rhos.
The tx frequencies and data timing are GPS-locked, but I'm sure there could be phase variation which could give phase variation of 1 - 9 beats per minute, as shown on your graphs.
I wonder if one of the projected new tx is currently testing on 12D
http://www.wohnort.org/DAB/ukloc.html#NWales

Andrew Webster,Wigan
Posts: 1864
Joined: 18 Sep 2014 16:03
Location: Wigan Northwest England
Contact:

Re: North West Wales mux 12D strange signal variations

Post by Andrew Webster,Wigan » 13 Oct 2016 11:33

Julian Hardstone wrote: The tx frequencies and data timing are GPS-locked, but I'm sure there could be phase variation which could give phase variation of 1 - 9 beats per minute, as shown on your graphs.
I wonder if one of the projected new tx is currently testing on 12D
http://www.wohnort.org/DAB/ukloc.html#NWales
Gwaenysgor 600 w 49 km is due to start on 12 D and that would boom in here as it's line of sight to here so I would expect to see an increase in signal strength.
Those oscillations happen any time of the day this morning the signal is more stable rising and falling slowly.

Andy
Receiving equipment: 2 Sony ST-S311, 1 Sony ST-SE520, 1 Sony ST-SE700 2 crossed FM 5s rotatable, 1 homemade FM 3 horizontal beaming S/E, 1 vertical FM 3 fixed beaming at Ireland, 2 element band 1.

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