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Yagi vs. Quad
October 1966 QST Article

October 1966 QST

October 1966 QST Cover - RF Cafe[Table of Contents]These articles are scanned and OCRed from old editions of the ARRL's QST magazine. Here is a list of the QST articles I have already posted. All copyrights (if any) are hereby acknowledged.
Here is a story of one Ham's experience in determining how the performance of his Yagi antenna compared to his identically configured (number of elements, height off of the ground, etc.) cubical quad antenna. His location was a farm field in Tennessee, back in the mid 1960s, so there was really not much in the way of obstacles to perturb signals arriving at one antenna versus the other, except of course when the direction of operation happened to have the antennas in line with each other. Both antennas were tuned for optimal performance at 14.22 MHz, which is in the high frequency (HF) band.

See all available vintage QST articles.

Yagi vs. Quad


An artist's sketch of the spacious antenna site of W4RBZ. The beams are mounted 80 feet above the ground on telephone poles spaced 150 feet apart.

Establishing Antenna Superiority Through Reception Reports

By Robert E. Fitz, W4RBZ

After more than 30 years of hamming from a series of temporary and semi-permanent locations, my first act upon retirement from the Air Force was to settle at a permanent location on a small farm in Tennessee and install a pair of the biggest telephone poles I could acquire.

The many discussions I had on the ham bands regarding the Yagi beam vs. the cubical quad led me to conclude that the ideal sport would be the on-the-air comparison of the two; I wanted to know exactly which antenna I should keep as the ultimate. These QSOs concerning the Yagi and the quad did not convince me that either one of them was vastly superior to the other. A big percentage of the quad men seemed only to be comparing their quad against tribanders or small beams that had been used in the past.

It seems to be pretty well established that at the lower heights a quad has a definite edge over the Yagi. However, I was curious to know how the two antennas would compare when both were placed at a relatively high elevation.

The merits of Yagis and quads have been expounded through the years, with it being a matter of opinion which antenna is the superior of the two. W4RBZ was fortunate to have enough time and real estate to erect both antennas and make on-the-air comparisons. Here's what he found out.
A 20-meter 4-elemen t commercial monoband beam was installed on one of the previously-mentioned poles. This antenna worked better than any antenna I had ever used before at any location. About two months later I installed a 4-element quad, using the fiberglass arms and aluminum spiders available on the market. A coax switch was mounted on the station control panel to permit instantaneous switching from one antenna to the other for a rapid cross check.

At the time this article is being written, I have used the two antennas for about three months and have checked both antennas with over a hundred stations. Most of the stations that I asked to give a comparative report were foreign; a definite effort was made to concentrate on the long-haul boys.

Any good engineer or analyst could point out a number of weaknesses in my system of comparison. This I will concede. I have only the standard test equipment available to the average ham; I don't have the capabilities for installing model antennas or conducting elaborate laboratory tests. My only motive was to determine whether a good commercial beam performed as well as, the same as, or better than a typical cubical quad installed at the same height at the same location by a ham of average ability with ordinary facilities and equipment.

First of all, a short description of the antennas is in order. The Yagi has a 36-foot boom and was adjusted strictly in accordance with the directions given by the manufacturer. The quad is mounted on a 30-foot boom in a diamond configuration and was originally installed using the dimensions given in a previous QST article1 and in use by a number of hams. Both antennas were peaked to a fundamental frequency of 14,220 kc.

details of the quad and Yagi antennas - RF Cafe
This photograph shows some of the details of the quad and Yagi antennas.
Each antenna is on a separate telephone pole and the boom of each is mounted exactly 80 feet above ground. The Yagi is about 30 feet closer to the shack, and is nearer to the highway and power lines; however, the quad is closer to some tall trees about 50 feet high. Both antennas are raised and lowered by similar elevator-cage hoisting arrangements.

As mentioned earlier, the quad was originally installed using those element dimensions that seem to be most commonly employed. During the firs two weeks of testing there was practically no difference between the antennas. Then the quad was lowered and completely retuned for maximum forward gain. This seemed to give the quad an edge on some contacts.

After the quad had been in use in this condition for about three weeks, one of the old antenna experts from the West Coast suggested that my quad still might not be peaked for maximum performance and suggested that I try his dimensions. This I did. The quad performance fell off noticeably. For the next 25 or 30 checks almost every station giving a comparison reported either that there was no noticeable difference between the antennas or that the Yagi had the edge. This was most noticeable on the long-haul contacts. Previously, VU2CK had reported on several occasions that the quad had about a one S unit advantage; after this change, Karnik reported that there was no noticeable difference between antennas. The same was true with several 9M2, 9M6 and VK9 stations.

The quad was again retuned for maximum forward gain, and tests were resumed.
 
I will only cite my experience with the Yagi and quad installation. In general, there was practically no difference in signal strengths on the short-haul contacts, and there was seldom any difference on medium-haul contacts to stations in Europe, Africa and the mid-Pacific. However, on the very-long-haul contacts to the Far East, Asia and the South Pacific, the quad had a fairly consistent 2-3-db. edge. On only a few occasions was there a big difference in reported signal strengths; this seemed to work both ways, with the quad being given a 2-3-S- unit advantage in a few instances and the Yagi given the same advantage in a few others.

On a number of checks, inconsistencies in the reports indicated that the different angles of radiation of the two antennas had pronounced effects. For example, on one occasion a JA, DU and YK6 were worked in quick succession. The JA contact gave the quad the edge, the DU reported the stronger signal from the Yagi and the VK6 reported no difference in signal strengths. Instances of this nature occurred frequently.

I learned early in the game that, under ordinary conditions of QSB and QRM, one switch-over between antennas did not give a valid comparison; the signals from the two antennas were generally so close in strength that several checks in quick succession were necessary for the other station to be able to give a fair evaluation.

While my quad seemed to have an edge on long-haul contacts, there were still times, under the varying condition of propagation, that the Yagi put out a stronger signal. The type of antenna in use at the" receive" end was definitely a factor. Shown below is a summary of my last 100 reports, the results of which are typical of my experience over the past three months. The quad was tuned for maximum forward gain for these checks.

number of stations to compare antennas - RF CafeWorthy of note is that there was never any reported difference on long-path contacts. This could be checked on only about a half dozen occasions, but no one reported any difference between antennas on the few long-path checks.

There are several factors, other than signal strengths at the" receive" end of the circuit, that must be given consideration in any final selection of the better of the two antennas. Even when tuned for maximum forward gain, my quad has a better front-to-back ratio: received signals were generally weaker off the back of the quad. The Yagi has stronger side lobes; a number of times, after checks with long-haul stations, a W station quartering off the side would break in to tell me that the Yagi appeared to be stronger during the test. This was also noticeable in reception. I also noted that during periods of heavy rain the quad had considerably less precipitation static.

On the other hand, the Yagi is much stronger structurally and mechanically. The Yagi was comparatively easy to assemble and raise. Constructing and installing a 4-element quad is like trying to handle a crowd of romantic octopuses. During periods of high winds the Yagi seems much more stable and less inclined to shake itself apart or to tear the telephone pole out by the roots.

During the tests I had lightning strike. At the time of the stroke, both antenna were grounded at the station through a Waters Protax coaxial switch.2 The Yagi, with its grounded boom, suffered no damage. The quad driven element was burned and cut in two and a small amount of damage was done in the station.

In summary, after three months of playing with the two antennas, I have found that neither is overwhelmingly superior to the other. I know I have two good antennas since they both perform well at my location. For the average U.S. contact or during QSOs of 2000-6000 miles, my antennas seem to run about neck and neck. The quad has demonstrated to me an advantage on the long-haul contacts that makes a difference in pile ups; however, this was not true in every instance. I have also learned that the quad must be carefully tuned at the actual site of operation to acquire this advantage.

I still have a lot of playing to do. I am now trying to figure out some easy way of tying the two antennas together and possibly feeding them in phase to see what happens; to date I have come up with no simple system of phasing two antennas 150 feet apart and at the same height. I would welcome any ideas on this score.

I also have a V beam aimed east and west. While I did learn that this antenna outperformed a tribander, I haven't yet gotten around to comparing it with my quad or Yagi on 20 meters. I also want to compare a Yagi "Christmas tree" against a triband quad; this I intend to do during the next few months.

I'm still not sure which antenna I will finally keep. Only when someone notices an ad in the back of QST listing an antenna for sale will it become obvious which antenna I have selected as the best for my particular station. However, I'll probably wind up keeping the antenna that succeeds in riding out the Tennessee summer thunderstorm season!


1 Bergren, "The Multielement Quad," QST, May, 1963.
2 Protax switches are not designed to protect equipment from a direct lightning stroke - Editor.





Posted  2/13/2013
 
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