Hi, Barry.
There are so many inconsistencies in this video if somebody wants to make a valid comparison. Of course, comparing any two antennas to obtain valid test data is a very complex process and requires a test range with fancy equipment and knowledgeable test engineers. For that and other reasons, for many years ARRL has refused to publish gain data from antenna manufacturers. It's so difficult to get right.
Looking at this video we see a small transmitting loop on a tripod and, very close to it, a very low horizontal endfed wire antenna, and all of this in a clump of trees. This is no "test range".
First, let's look at the loop. A "small" transmitting loop is one where the circumference is about 0.1 wavelength or so. It's short enough that the current in the loop is constant all the way around. The inductance of the loop is resonated with a capacitor to create a parallel tank circuit. At resonance the current in the loop can get very high and the voltage on the capacitor can get VERY high. As in any antenna, this high oscillating current is what causes the RF radiation.
An effective small loop wants to be as big as possible without exceeding 0.1 wavelength. Because of the high resonant current, the loop conductor wants to be LOW resistance. That means fat, no joints, solid copper (or silver if you have some laying around.) This means a solidly-welded copper pipe with no joints for best results. RG8 braid will work but with greatly reduced efficiency. The capacitor is the hardest thing to get right. It has to handle the high RF current as well as handle upwards of thousands of volts. That's why most all field portable loops limit you to about 20 watts. For 100 watts you're talking about a vacuum variable capacitor or some other hefty arrangement.
Can a small loop be an effective antenna? Yes. Definitely. But nothing is free. Antennas can have three desirable characteristics: high efficiency, wide bandwidth, and small size. At best you can have two of these. An iffy antenna might have just one. A
good small loop can be, well, small, and have good efficiency. It will NOT have wide bandwidth. It will show "high Q". The bandwidth of a good small loop might be a few kilohertz. If a small loop has much more bandwidth than that it's probably quite inefficient. A small loop is vertically polarized. That's why you can get decent results at low height, as on a tripod. Since it's self-contained electrically it doesn't require a ground system. That's nice when you're in the field and have no options to hang a wire.
Now, onto the End Fed Half Wave wire antenna. End feds are handy for portable operation being very packable, light weight, and sometimes handier for managing a feedline than a centerfed dipole. Other than the handy factors, end fed halfwave antennas aren't magic. They do the same thing as a dipole. A horizontal dipole is going to be sensitive to its height above ground. When it's a quarter wave high or higher, a horizontal dipole or end fed can be a very effective antenna. It can be efficient and it can have good bandwidth. But it isn't small when deployed and it requires one or more supports.
Conclusions:
Can a quality small loop outperform a very low endfed? Yes it can!
Can a small loop outperform a high dipole or endfed? Eh, maybe. But the half wave will be less fussy to tune, less sensitive to its surroundings, handle more power, and be way cheaper. But you can't stick an endfed on a tripod.
Can you make a rational head-to-head comparison between the two antennas on one frequency and one target area and one moment in time? Eh, not really. Due to many propagation factors, even two
identical antennas in different positions can give different results that make one seem better than the other.
So, Barry, you ask me the time and I tell you how to build a clock.
73,
Chuck
NA3CW
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