Reception wall?

[jetset]

Can anyone give any thoughts as to what could cause this apparent brick wall reception limitation in the North East of my polar diagram?


I'm not aware of any obvious obstructions in that direction.

[ACW367]

The brick wall is the airway linking the Northeast UK with Amsterdam.  Because of the north sea military ranges there is very little route variation by the ADS-B airliners.  I'm guessing you don't have the range for the next airway further out over the north sea.

[jetset]

Thanks but I don't think that's the problem.
Here's a screenshot of Flightradar


Here's my box showing 2 planes heading for the brick wall which get time-outs when reaching it. 

[Runway 31]

Stephen

I would suggest that you are at the limit of your range as you are around 175 miles out there so I wouldnt be concerned as looking at the polar diagram it is no less then in any other direction apart from a few spikes.  The north east is not any different than the western side in fact it is a bit better being constant with the 179nm cirlce whereas the other side is consitantly less than the 179 nm line.  The east, south and south west are showing a lot less range than the north east.

A 350 mile radius is not to be sniffed at and I wouldnt worry about it.

Alan

[bratters]

I think the problem is probably topographical.

Bear in mind 2 points -  line of sight and aircraft altitude.  Like you I'm fortunate in having a 360 view but I have directions where reception is down. One is to the flat east which was a surprise but can be explained by a chimney being sufficiently close to blot out a surprisingly large arc.

Another is a wall is to the north - this is caused by intervening hills/mountains - requiring an altitude of 35000 plus  on the extreme edge of my diagram for a signal to be obtained.

Try a few doodles on piece of paper involving ramps and rising straight lines and you might be able to find the blocks on a map.

[RodBearden]

To aid in your experimentation try the Heywhatsthat profiler Up In The Air feature and try different antenna heights:
http://www.airnavsystems.com/forum/index.php?topic=3335.msg31610#msg31610

Rod