Primarily for general aviation discussion, but other aviation topics are also welcome.
#1710471
So having booked a couple of weeks off work, and planned several trips , this pops up in my sky demon notams today :evil: :evil:

GNSS signal jamming trial. GND jammers located within 3NM radius position 520053N 0033831W (Sennybridge, Powys). Activity may affect aircraft within 122NM radius of site. Emergency cease jam contact 01874 635599 or 01980 957597. During trial GNSS REC may suffer intermittent/total failure, or give incorrect position info. Crews should be aware of these limitations and use alternate means of nav. For INFO 01874 635599. 2019-08-0283/AS4
Schedule: 0700-1600
#1710490
Worst case areas of effect against a receiver:

2m AMSL - Areas with clear line of sight to the transmitter site.

25m AMSL - Areas with clear line of sight to the transmitter site.

70m AMSL - Areas with clear line of sight to the transmitter site.

5,000ft AMSL – Up to 100 km (54 nm) in all directions.

10,000ft AMSL – Up to 105 km (57 nm) in all directions.

20,000ft AMSL – Up to 110 km (60 nm) in all directions.

30,000ft AMSL – Up to 112 km (61 nm) in all directions.

40,000ft AMSL – Up to 113 km (62 nm) in all directions.

#1710529
From the OfCom site quoted above it seems that there is rather more to it than malcolmfrost has presented above. The FULL content from OfCom in respect of this trial ais as below (my bold):
Notification of GPS jamming exercise: Sennybridge, 5 – 23 August 2019
Dates: The exercise will run over the period 5 – 23 August 2019.

Times: 09:00 – 18:00.

Frequencies: 1559 – 1612 MHz, 1215 – 1256 MHz, 1160 – 1214 MHz.

Location: Within 5km of Dixies Corner, Sennybridge. SN 874 364.

Worst case areas of effect against a receiver:

2m AMSL - Areas with clear line of sight to the transmitter site.

25m AMSL - Areas with clear line of sight to the transmitter site.

70m AMSL - Areas with clear line of sight to the transmitter site.

5,000ft AMSL – Up to 100 km (54 nm) in all directions.

10,000ft AMSL – Up to 105 km (57 nm) in all directions.

20,000ft AMSL – Up to 110 km (60 nm) in all directions.

30,000ft AMSL – Up to 112 km (61 nm) in all directions.

40,000ft AMSL – Up to 113 km (62 nm) in all directions.

Dates: The exercise will run over the period 5 – 23 August 2019.

Times: 10:00 – 12:00, 14:00 – 16:00.

Frequencies: 1559 – 1612 MHz, 1215 – 1256 MHz, 1160 – 1214 MHz.

Location: Within 5km of Dixies Corner, Sennybridge. SN 874 364.

Worst case areas of effect against a receiver:

2m AMSL – Areas with clear line of sight to the transmitter site.

25m AMSL – Areas with clear line of sight to the transmitter site.

70m AMSL – Areas with clear line of sight to the transmitter site.

5,000ft AMSL – Up to 180 km (98 nm) from the transmitter site within a 225°- 270° arc, up to 120 km (65 nm) from the transmitter site within a 177° - 185° arc and up to 100 km (54 nm) in all other directions.

10,000ft AMSL – Up to 195 km (106 nm) from the transmitter site within a 225° - 275° arc, up to 190 km (103 nm) from the transmitter site within a 150°- 190° arc and up to 105 km (57 nm) in all other directions.

20,000ft AMSL – Up to 210 km (114 nm) from the transmitter site within a 160° - 265° arc and up to 110 km (60 nm) in all other directions.

30,000ft AMSL – Up to 220 km (119 nm) from the transmitter site within a 160° - 265° arc and up to 112 km (61 nm) in all other directions.

40,000ft AMSL – Up to 225 km (122 nm) from the transmitter site within a 160° - 265° arc and up to 113 km (62 nm) in all other directions.

So for part of the day, at say 5,000' it covers roughly a triangle between D203, Camsore Point on the SE tip of Ireland and D001 in the Bristol Channel off Newquay, with a further quite narrow lobe running about due South from D203 as far as about Tiverton. There also seems a bit of inconsistency about the timings - the NOTAM states 0700-1600 (UTC) whereas the OfCom message says 0900-1800 (presumably BST , but even than an hour different :roll: )

*EDITED to correct 180 degree error in my description in my final paragraph of the position of the main area, which I originally, wrongly described as reaching Milton Keynes and Sheffield (hence the references below to my incorrect description, now corrected. :oops:
Last edited by Stu B on Mon Aug 05, 2019 6:08 pm, edited 2 times in total.
Dave W liked this
#1710531
Stu B wrote:So for part of the day, at say 5,000' it covers roughly a triangle between D203, Milton Keynes and Sheffield, with a further quite narrow lobe running about due South from D203 as far as about Tiverton. There also seems a bit of inconsistency about the timings - the NOTAM states 0700-1600 (UTC) whereas the OfCom message says 0900-1800 (presumably BST , but even than an hour different :roll: )


That isn't shown on the charts in the Pink AIC (no good giving a link as it'll expire.)
#1710557
Is this a good time to say I'm looking at an autumn/winter programme for my Masterclasses? Far more than just infringements (and cheaper than infringing) but in the nav tips module look at GPS/TradNav integration including seamless transition 'if the ipad overheats and shuts down' (just like mine did the other week, but 'works' for GPS jams or power exhaustion too). I seem to have 5 interested around Wilts/Dorset (I am told) and possibly the same somewhere in the Goodwood-Shoreham-Redhill triangle
#1710579
Paul B said
That isn't shown on the charts in the Pink AIC (no good giving a link as it'll expire.)

I just did a rough plot of the coverage shown in the OfCom announcement:
"Up to 180 km (98 nm) from the transmitter site within a 225°- 270° arc" and
"up to 120 km (65 nm) from the transmitter site within a 177° - 185° arc."


I would have thought that the OfCom statement was the authoritative source rather than the AIC?
#1710582
Stu B wrote:Paul B said
That isn't shown on the charts in the Pink AIC (no good giving a link as it'll expire.)

I just did a rough plot of the coverage shown in the OfCom announcement:
"Up to 180 km (98 nm) from the transmitter site within a 225°- 270° arc" and
"up to 120 km (65 nm) from the transmitter site within a 177° - 185° arc."


I would have thought that the OfCom statement was the authoritative source rather than the AIC?


It's a good job that the AIC says not for operational use then isn't it? :lol:
Stu B liked this
#1710599
Stu B wrote:I just did a rough plot of the coverage shown in the OfCom announcement:
"Up to 180 km (98 nm) from the transmitter site within a 225°- 270° arc" and
"up to 120 km (65 nm) from the transmitter site within a 177° - 185° arc."


I would have thought that the OfCom statement was the authoritative source rather than the AIC?

Isn't that exactly what is plotted in Appendix 2 of the AIC? I don't see it getting anywhere near Milton Keynes or Sheffield.
#1710634
Whoops - mega-embarrassing mistake on my part, I had plotted the reciprocal of the boundaries of that arc! So the size is correct but it is located in an arc from SW of Sennybridge to West of Sennybridge - which covers the coastline from about Pembury to just S of Aberporth - but it extends well out over Bristol Channel and the Irish Sea, almost to the Irish coast W of Sennybridge. Does that look more like the AIC (which I confess to not having searched for.)
I had got the spike down to Tiverton right, though!