[UK-CONTEST] Aircraft Reflection Path Plot

[Ray James]

Hi Ken,
Having checked the path plot between GB3ANG (IO86MN) and your location in IO81WV, air traffic between Manchester and EI would not be useful to you.
That path is too far south west of the mid-point which in your case is between Kendal and Settle.
The east/west Manchester/EI path is also "side-on" to you which is not the most favourable anyway. 

They can produce reflections but of far shorter duration than those travelling in or close to the path your directing to.
Your actual mid-point towards ANG is very flight active, being on a regular flight path and should produce superb results. 

However, the path plot between you and IO67UF identifies a mid-point in the Irish Sea triangulated between Whithorn, St Bees Head and the northern tip of GD.
This is definately not on a regulally used flight path so opportunities to hear the Isle of Skye beacon will be rare but not impossible.
Like a HF contester would plan ahead with greyline knowledge, propagation forecasts and more, this is an area were VHF+ contesters can optimise potential results.
Use of regular flight paths can give very good results, even by chance and without recourse to knowing when a reflection opportunity is available though it helps a lot to know so as not to waste time.
Use of rarely used flight paths opens up opportunities to work rarely worked or heard locations/multipliers. In your case, IO67.
Yesterday for example there were numerous opportunities.

05.55 DAL6      767-400  Detroit - Heathrow    33,000'
08.00 VIR206   747-400  San Francisco - Heathrow   37,000'
10.15 ICE542   757-400  Keflavik - Paris   39,000'
10.25 BAW48   747-400  Seattle - Heathrow   33,000'
16.25 BAW9     747-400  Heathrow Phoenix   31,350'
22.00 ICE455   757-200  Heathrow - Keflavik   38,000'
22.20 DHK972 767-300 East Midlands - Cincinnati   31,975'    


In relation to the total UK/EU to/from North American air traffic in 24 hours then that is a very small number and even the majority of those were in my opinion borderline cases but possible due to the wider beamwidth of a 4m antenna over what I'm used to on the likes of 70cm, 23cm and 13cm. Only the first two were in what I would consider prime mid-point positions and there were a fair number of other G/GM flights that veered west of the Cumbrian coast that could  possibly have produced an audible signal from the beacon and if not, certainly a visual trace using Spectran or other waterfall display of your receiver bandwidth.
The method I used to determine these possibilities is very easy.
Establish the mid-point using the SM7LCBpathplot software on his website. 

Go to www.planefinder.net 
Zero in on UK airspace and in particular the midpoint area you are interested in.
Click on the "Playback" icon.
Set a date from the calendar.
Set a start time.
Set the speed of playback. I usually use 120x normal.
When you see an aircraft approaching the mid-point circle (as indicated on the pathplot map) then hit the pause button to enable you to pause everything and click on the jet to identify everything about it including the height.

Range depends on numerous factors of which height and the size of a jet (area of reflection) are the most important.
You're 650km from GM8RBR's beacon. Something over 800km is the maximum I believe for a jet at 40,000' so you are very comfortably within that.
An SBS receiver would be useful for portable stations where no internet connection is possible but range would be a negative as I believe that even with a very effective 1,090MHz antenna there's a limit of about 400km.
That's fine for seeing traffic within 400km but it is important to know what is further away than that and coming closer so you're prepared for a maximum range contact (or CQ calls) on both inward and outward flights and not just outward.
As you say, the online resources are free and provide all the advance notice you need.

Good luck!

73 Ray GM4CXM



  




________________________________
 From: Ken Eastty <ken.g3lvp at btinternet.com>
To: uk-contest at contesting.com 
Sent: Monday, 9 January 2012, 22:50
Subject: Re: [UK-CONTEST] Aircraft Reflection Path Plot
 

  Aircraft Reflection Path Plot (Ray James) -

Thanks for that Ray, this is no doubt the mechanism which permits 
reception of GB3ANG here (IO81WV) on 2 & 4m for most of the time 
providing there's plenty of traffic in the airway between Manchester & 
EI. It's a pity that the plots don't include the height at which an 
aircraft would have to be flying for it to be 'seen' from both ends of 
the path but I suppose that it only takes a few moments to calculate it.

So far I've not heard GM8RBR's  new 10W beacon on Skye (IO67UF) on 70.1 
Mc/s except via ms. The typical height of most airliners would seem to 
be insufficient to act as a reflector over this path.

73...

Ken

G3LVP
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