Many moons ago, I wrote about a comparison I ran alongside an operator in south Wales - about 125 miles away from me. He's near the sea, runs a 4-element SteppIR, and runs about 400W.
So, it was a bit of a surprise - not accepted by some - that my simple delta loop was being heard at the same signal strength by the same operator, at the same time, on the US east coast, as the south Wales station.
To me, this is easily explained. It's the terrain, stupid!
Living on a ridge, with ground that slopes initially steeply, then gently to the coast, is of enormous benefit in terms of ground gain. According to the ARRL HF Terrain Assessment model, my 3-ele Yagi gets a ~7dBi boost from ground reflections, even with the antenna being set at no more than 6m high. What's more, that total peak gain of over 14dBi occurs at just 2.5 degrees above the horizon. By lowering the antenna to about 4 metres above ground (remembering we live on an elevated plot), the peak gain comes down to just 1 degree at 14dBi. That is very tough to achieve from most sites.
True, DX doesn't always come in at such incredibly low angles. But more often that not, access to very low angles is of benefit, not hindrance.
Now, I saw the same thing happen again this week. A west Wales operator this time, operating a 3-ele SteppIR (the make of the antenna is irrelevant, of course). I don't know the power in use, but that's OK, as I didn't have a chance to make contact with the US station, so it's a listening test only.
The result? The station was a 5/5 to me on a delta loop with base at 1.8m, and 5/5 to the other operator on a Yagi up at about 10m. No difference!
OK. You are probably not convinced just yet. That's understandable. So, let's look at how the ARRL HFTA software models the gain for both stations. This time, I'm comparing identical Yagis, except mine is only 6m up on the tower, whereas the west Wales Yagi is set at 10m.
Are you starting to warm to the argument now? My gain (blue) is +14.3dBi at 2.5 degrees, whereas the SteppIR in west Wales (red) is way, way down at minus 2.5dBi at the same elevation. Rather self-evidently, the other station stays well down on gain until we reach parity at 11 degrees, beyond which the west Wales Yagi then has a marginal advantage for a while.
So, whilst I again stress and accept that not all DX comes in low, a lot of it does. So, a lot of the explanation for the ability of my simple wire antennas to match the gain of big, expensive antennas atop big, expensive towers, is likely to be in the advantage of my terrain.
True, I haven't compared the delta loop against a Yagi, which was my original position. That's because HFTA can only handle horizontal antennas; my delta is vertically polarised. However, whilst ground gain is likely different, the delta is able to access very low angles, due to the sloping ground in front of it in most directions.
Antenna modelling with MMANA-GAL suggests that my vertical delta has anything between 4.4 and 7dBi gain, and real RF measurements confirm the radiation is at or only slightly above the horizontal, i.e. 0 degrees.
So, if we take the worst-case gain for the delta, at 4.4dBi, that still puts it at least 5-6 dBi ahead of the 3-ele Yagi at 10m in west Wales until at least 5 degrees elevation - and that's without any ground gain included for the delta!
In short, if you want the best location for DX, don't take my word on what to look for. Take that of the great Les Moxon, who, according to an acquaintance of his, would only choose a hillside location for a new home - explaining his vivid accounts of milliwatt SSB QSOs between himself and VK land!
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