Yagi vs. Delta Shoot Out!

Well, having come up with a lightweight, strong design for a 2-element loaded yagi, up it went, by moonlight, for tests the following early morning.

A 2-ele beam like mine.  Large, and needs to go up high.

Now, I was not able to put the beam up at anything like a good height - just 6m, though the ground does slope away sharply in front of it.  So what follows isn't an assessment of what the beam could do if it were at greater heights.

I turned the beam towards the long path signals from the Pacific.  Running at the other end of our large garden, away from any interaction between them, was my trusty 20m full wave delta loop which uses vertical polarisation.

Wow!  A SteppIR in a very macho scene.  It gives a good impression of the sheer size of even a simple 2-ele beam.  But the sad reality is that experienced beach operators will tell you that a simple vertical antenna easily outperforms a yagi from the seaside.  So 'beam' doesn't necessarily mean 'best antenna' for all locations.

Luckily, VK3VCE and VK5PAS were in a group that were only too willing to report on the two antennas.  The result?  The beam was between 1 and 2 S units down on the delta loop.  This was confirmed later in the day, when a station on Prince Edward Island also came in 2 S points down.

Propped up by an 8m fishing pole and made of any old wire, the delta, with its base at just 1.2m, beat the far more complex beam by anything up to 12dB.

So, in terms of decibels, that's a beam, at this height, returning 12dB less in and out firepower than a simple delta loop.

Now, again, the beam wasn't being given a fair chance, and it is a centre-loaded, shortened version.  BUT!  Let's look at this from the perspective of ease of deployment, use, and cost.

The beam is complex to get up into the air.  Books and magazines suggest it's easy, which it is if you have lots of money, plenty of room for guy wires, and permission to put a mast of some sort up.  For real hams, it's really very difficult; have a look at how wrong it can go if you're not prepared:



Then you need to rotate the beam.  This adds considerably to the expense, and necessarily means you'll have to twist your antenna around endlessly to get the best signals.

Then you'll need to make the whole thing windproof at, for 20m antennas, anything from 8-15m high, depending on whether you have any ground reflection sweet spots.  For me, with regular gusts to 80mph or more, this is a big ask, or a recipe for endless upping and downing the beam.

Big antennas can mean big disasters and high repair (or insurance) costs. 

Given that my 2-element beam would appear to have to reach at least 10m before it broke even with the delta loop, with an apex at 8m, supported by a single, $15 fishing pole and which resists winds to about 50mph quite happily, the beam loses the competition, hands down so far as my essential check list is concerned.

Low angle patterns typical of low-mounted, vertically polarised deltas.  This one's at 5m; at lower base heights, the upper lobe vanishes.  Low angle patterns are very useful for DX, and the delta excels in this respect.

Now, my QTH does have a clear aspect, is elevated at about 65m around the surrounding land, has some sea views, and has the best terrestrial ground you could hope for.  So a delta may not work quite so well from a cluttered environment, where a yagi placed above the neighbourhood would yield real benefits.

Just keep in mind that, whilst a horizontal beam sounds like a good idea, the reality isn't necessarily so.