On the final day of XT2TT worked them QRP while testing the Quad. Also 9M6 was very loud S9+10 while my quad was pointing to east. Pileup was over 1k wide. I gave my call twice “oh3t/qrp oh3t” and he came back immediately with oh3 oh3 5nn. Very rewarding to test the antenna with good results. I have to admit that I used my old yagi for working Clipperton team TX5K, since I am still a bit hesitant to put kw through my tuner-work-in-progress.
Antenna Bandwidth
Antenna bandwidth is critical aspect of design. I am suffering from snow and icy conditions at least 4 months each year. Resonant antennas can not be designed to be very narrow, since the snow and ice will alter the resonance point and swr significantly.
The yagi design that I have been using as the reference for comparison with the quad can be seen below. I used eznec to calculate the swr and optimized the feed impedance to correspond whet it would look like with the matching stub or for example gamma feed (pick your favorite).
As can be seen from the plot the feed impedance for this 3 el yagi is reasonably low. I used 15 ohm as the feed impedance for drawing this plot.
The reasonable feed swr can be considered to be below 2 for the antenna. The low point for swr < 2 is 14.14 MHz (the upper figure) and the high point for < 2 swr is 14.36MHz. So the < 2 swr range for this antenna is 200kHz. This is fine for example 40m band in EU and plenty for 17m and 24m WARCs but for 20m this is unacceptable.
The point here is not to start optimizing the 3 el yagi but to demonstrate that narrow yagi designs that are optimized for gain and f/b may lead into trouble. Personally I am not a big fan of traditional yagi designs, but prefer the modern OWA designs because of the winter conditions.
Quad and Bandwidth
Traditional quad antennas are equally narrow. One of the main reasons for opting to go with the HRSQ design is the tough winter conditions. The HRSQ is tuner fed, and antenna can be tuned regardless of the snow, ice, and rain. However, the pattern will change as I have already demonstrated in previous analysis.
But lets go extreme. If the resonance point is shifted down and tuner is used to put the antenna into resonance and swr 1.0 the pattern will change.
Plot with 13.5MHz will revert the pattern, the gain is few dB below the nominal, f/b is destroyed, but I can still keep on working and make contacts with full power.
This plot is drawn with 14.5MHz. The pattern has similar characteristics to feeding way below the nominal frequency. The gain is again below the design, but contacts can be made with full power.
Clearly this design due to its nature of feed with tuner and force feeding the antenna has its benefits in tough winter conditions.
HRSQ is clear winner in bandwidth.
Turning Radius
One of the critical design criteria for my tower was to be able to stack the antennas. Stacking has the impact of increased gain and better control over the launch angle. Stacking has also the impact of really pushing down the launch angle below 5 degrees with good gain.
In order to stack antennas one has to avoid the guy wires. High gain 15 and 20m yagis require long booms and in case of my tower setup I do not have the real estate to spread out the guy wires to accommodate long boom yagi stack. Further, I studied the different monoband and multiband yagi options and always run into problem with the guy wires. So I had to optimize the turning radius.
The turning radius for these antennas were calculated for the modeled yagi, HRSQ in diamond and “standard” quad configurations.
| Antenna | Turning radius, meters |
| Yagi | 4,22 |
| HRSQ Diamond | 4,27 |
| HRSQ square “standard” | 2,5 |
So the monoband 20m yagi has a similar turning radius than the HRSQ in diamond configuration, but 1,7m longer than HRSQ in square configuration. So we have a clear winner.
Summary and Final Words
These three articles were covering comparison between quad and 3 el yagi.
Based on the simulation results I would conclude that very few quad myths actually hold true. Quad is not equal to 3 element yagi. Quad is no more fault tolerant to construction errors than yagi. Yagi is clearly better in all performance related metrics compared to quad.
Yagi is the very clear winner in this comparison!
Quad wins in turning radius, and especially HRSQ wins in antenna bandwidth, but that comes with the extra burden of high power tuner in the feed system.
So, how reliable is this comparison? Based on my experience from the models which I have done and the results from field tests and on-air performance comparisons I was referring earlier, the results are very close to what you will get from these antennas.
Of course, quad and loop antenna enthusiasts may say that it is not fair to compare monoband yagi with multiband quad and declare the yagi as clear winner.
Yes I agree, it is not fair. Monoband yagi is superior antenna, but the quad design is very easy to multiband. The point was to demonstrate that quad is very close to yagi, but not superior. The benefits of quad design comes in the next acouple of sentences. In fact all the results and plots in the articles were from monoband yagi and multiband quad. But the results for quad are what they are, even in the multiband setup. So basically, I would say it is reasonably fair to build a quad that is close to 3 el monoband yagi, and get 4 bands for “free” without compromise in performance! It is very fair!
Thanks for reading!
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