At the risk of reopening the worm-can, I've two technical questions for anyone who can reduce my ignorance, and particularly for DC_Ed and Chock (who know a bit about the subject) brought to mind by reading another thread here...I don't fly (except in FS9 and FU3), but work in industrial electronics and am curious about all things radio & RFI.How does a coastline distort VOR signals?How does the NDB/busy-thundercloud thing work?Cheers chaps,D

I'll tackle the second. The ADF arrow will sometimes point towards lightning activity because lightning discharges are in the same low frequency range as NDBs. The most I've ever noticed was a slight jitter one evening while going around a huge cell."Poor man's radar" or "Poor man's strike finder".

Hey, thanks for the vote of trust :( 1. If I'm not mistaken, the disruption in the VOR signal has to do with the "reflectivity" of the surface (land vs. water). I think Chock is going to answer this in a more elaborate way.2. I think Zach got it alright. I've seen it a couple of times too and it can be from a little jitter as Zach says, to a big (i.e. some 30 degrees) oscillation

With regard to distortion of nav aid signals, both NDB and VOR signals are affected when the signal crosses a coastline at an oblique angle, and are also further affected if a nav beacon is quite a way inland and you are over water and receiving that signal. Ed is indeed correct, the distortion is caused by the different energy absorption properties of land and water for radio signals. The recommended solution for this problem is to use a nav aid that is close to the coastline if you are over the water.It's certainly less of a problem in the continental USA of course, where many flights don't even get near a coastline, but in the UK it is fairly common to find yourself over a coast line on a flight, especially for PPLs who are doing the European version of the 'one hundred dollar hamburger', by flying across the English Channel to an aerodrome in Northern France, since they will probably be tracking nav aids in the UK and France when over the Channel. Strictly speaking, crossing the Channel is not that big a deal, since it is only 21 miles at the narrowest point, you can actually glide across with enough altitude, but in IMC it might be useful to stay on track, since there are specifically defined crossing areas for inbound and outbound traffic from France to the UK. That is probably why the following question crops up in the IMC Rating exam in the UK...When flying over water using the ADF, coastal refraction is kept to a minimum by which of the following?A. Using an NDB that is well inlandB. Using the BFO facilityC. Using an NDB that is on the coastD. Flying lowerThe answer is C, because doing that will minimise the distortion owing to the fact that the signal doesn't travel a long way before hitting the coast and bending, so the distortion would not produce a large refraction of the signal. Also, the closer you are to the signal, the less it actually can be out of true anyway, so it makes sense to use one that is nearer to you.I wouldn't worry unduly about this phenomenon by the way, since you can cancel out the effect of it by triangulating your position with several nav aids, and they would probably average it out to a reasonably accurate position, and I suspect the only reason it gets brought up is because they like to ask you tricky questions on the IMC Rating test. I don't think FS simulates this phenomenon as far as I'm aware.Al

Thanks chaps.It's a pity the effects aren't modelled in FS but it's a good day anyway- I learnt something! The subject may keep my curiosity entertained for some time.RegardsD

On the NDB and lightning. I believe that if you are near a storm and you tune the receiver off station you will see the needle drift over the the general direction of the lightning strikes. I think that is the way the Ryan stormscope works. Not super accurate but better that nothing.P