G/LD-017 Red Screes

I’m showing the real bulge/curvature of the earth over the distance, and an absolutely straight line (i.e. a Euclidean straight line, not a GR geodesic) between points - no refraction taken into account. It may not be as relevant to radio as the example you give, but it is what it is, and the thing is still in development as I scribble.

With just a little work, I could also include any number of k factors (Special K only for those with accounts and deep pockets)…

Ah, I think I see what you mean by your masterfully concise sentence - is it that the Fresnel zone ellipsoid should be arranged around a curved path, with curvature determined by the factor k, rather than along my straight line? That would seem sensible. Time to build in a k-factor dropdown just like how them pro’s do.

OK, so the program now includes various k factors, including 1.333, as options in a dropdown. Thanks for pointing out that this has to be taken into consideration. Here’s how that path between Windermere and Snowdon GW/NW-001 looks now:

HTH, Rob

I read the article that G3CWI linked to yesterday, but didn’t pick up on the K factor until I read it again today.

If I understand correctly the K factor allows you to draw straight line propagation paths between points, rather than the actual curved path due to refraction, by fudging the Earth’s radius a bit so it is flatter than reality? I think I understand that K won’t change other than where you are on the Earth’s surface, presumably because the Earth isn’t quite round?

It also means we are back to the possibility that there does exist a path between here and Snowdon. I need to start looking at the Welsh alerts again, clearly :sunglasses:

Cheers, Mark. M0NOM

That’s about the long and the short of it: RF engineering firms use these factors when considering things like microwave paths between stations. There’s quite a lot of references and literature on the subject, some going into quite a lot of technical detail.

Basically, these k-factors are used in order to simplify the graphical representation of a signal as it propagates through regions of the atmosphere having slightly different refractive indexes. These refractive indexes depend variously on atmospheric pressure, CO2 and water-vapour content, and hence on elevation and weather conditions. So, it turns out that most RF engineers tend to use just two or three standard K-factors when designing microwave systems, instead of analyzing the atmospheric conditions on the day and making complex calculations.

So, it’s rather more than the “tinker’s fudge” I thought it was when I retired last night, but I think we’ve got it covered now… :smiley:

Rob

Did you not read the bit about troposcatter a few posts back? The answer to your question is yes but you’ll not do it without directional antennas.

I’m OK on the troposcatter as you explained it earlier - what about Es, sporadic E? Which of those is most important in getting a 2-meter signal from GB to Spain, for instance?

When there is an Es opening to Spain (perhaps several or more times a year) signals can be phenomenally strong. I’ve never heard a strong tropo signal from Spain though others have been more fortunate.