The Quad Antenna

 

Becoming a ham in the winter of 1959-60 it's obvious that I've had a few years of playing with antennas, I don't have an exact count, but counting all antennas LF up to UHF it's way over 100 different ones, wire and beams..  The one antenna I would match up to anything on the market is the Quad, even the StepIR that has such a huge hype right now can not compare element for element.  You ask, why then don't I have quads now?  At age 54 I developed a problem with my wrists and hands that the doctor told me to stay off the towers, finding good help to climb towers is hard to find, so it was time to keep things simple.

If we look at all the advantages and disadvantages of quad verses beam we come up with the quad's biggest disadvantage, it's three dimensional rather than two and depending on materials used can be a real headache with ice.

Lets start out with a simple comparison, two element quad verses three element beam, and simply one band.  We'll assume these are cut perfect and the utmost is obtained for both.  The quad will have more gain at any given height and actually perform at 40 feet as good as a beam 15 to 30 feet higher.  25 or 26 DB front to back is about the most you will every get from a beam, while I've seen over 30 DB with a quad.  The quad can produce 60 DB side nulls which at times can be very useful.

Now lets make them tri-banders or five-banders.  Using the boomless method for the quad where the spreaders slope forward for the driven and backwards for the reflector, we can now keep almost perfect spacing to keep the gain and front to back very good on all bands.  The beam on the other hand will have to have at least three elements with traps and then additional elements mixed in to get somewhere close, adding to the weight dramatically and a lot more interaction between elements.

Now if this has kept your interest, the following information and pictures are of quads I have built and most definitely work.  Keep in mind there are different materials and methods other than what I used, but these were built for durability and cost effective.

 
Simple 2 Element 5 band Quad

This is actually a 7 band quad as 6 and 2 meters were added with two additional spreaders.  It was built by N8BNE in the fall of 2005 using Cubex spreaders and a 10 foot boom.  The wire is number 12 copper motor winding wire and the matching stubs are RG-11 using the following measurements.
 
Frequency Driven Drill Points Reflector Drill Points Stubs
14.200 69’3” 12’3” 72’9” 12’10 ¼” 11’0”
18.118 54’3” 9’7” 57’0” 10’1” 9’0”
21.300 46’2 ½” 8’2” 48’6” 8’6 ½” 7’8”
24.940 39’5” 7’0” 41’5” 7’4” 6’6”
28.500 34’6 ¼” 6’1 ¼” 36’3” 6’5 ½”  5’6”

 
If you want to know how this antenna works at 32 feet just ask Larry, N8BNE.
 
Over the years I tried many different pieces of hardware and as far as spreader arms go, I find what Larry used, (Cubex), to be probably the best, although a little expensive.  I found taking two pieces of 2 inch angle aluminum 1/8 inch thick approximately 2 to 2 1/2 feet long bolted together and fitted with 2 inch muffler clamps was about the least expensive method and very strong.

Spreaders or elements have been tried from solid fiberglass, tapered hollow and bamboo.  The spreaders that I found to last the longest and withstand Michigan weather was bamboo sealed with Scotch 33+ tape, it will take at least two large rolls to do one spreader.  Don't use cheap electrical tape, it will come loose and you will end up with many flags after the first winter.  The Scotch 33+ will stay tight and keep the water out for many years, the spreaders Larry used had been in my barn for about 10 or 11 years and were removed from quads I had built over the years.  Some of those were 15 to 18 years old.

Don't drill holes to put your wire elements through, they were only called drill points by the fiberglass manufactures, they will only cause weak points in your spreaders.  Early years I only used electrical tape to connect the wire to the spreaders, but now the tie raps work great to get the wire nice and tight, and then tape.  Also using large tie raps to connect the spreaders to the spreader arms and then taping works great.  Always seal the upper spreaders so water can not build up in the tape and the same to the bottom, as this causes real problems when it freezes in the winter.
 
Now that we have covered the fundamentals, here a some quads from the past that really worked, but remember we didn't have WARC bands when these were built. If you have built a multi element four or more element five band screamer, pass it along and we'll put it up here also.

 
4 Element 20-15-10, 1977 on 80 foot of tower

This was one of my first quads that I actually took a picture of, it was built on a 24 foot boom.  The 80 foot tower was centered in my back yard, 65 feet by 65 feet using a 4 way guying system.  This one helped put me over 100 countries for my DXCC.
This was the same antenna over a year later erected at new QTH at Concord, MI, tower increased to 96 feet and I now had 18 acres to play with and spring was just around the corner.


 
The Big One!

This is the only picture I could find of the biggest quad I ever built.  34 foot boom holding 7 elements, 4 on 20 meters, 6 on 15 and 7 elements on 10 and 6 meters.  I held a QSO with this one which may be a record, I talked to my friend Rod, ZL3FM SK now, from 9PM local time till 10.15AM the next morning 13 hours and 15 minutes on 20 meters.  No time during the QSO did his signal ever go below S7 with 95% of the time S9 up to 30 DB over.  Antenna was only up from April to mid July of 1979 when 75MPH winds caught it sideways and snapped the 3 inch boom in half.  I guess I should mention, yes that was yours truly up there.

This was a reconstruction of a similar antenna without 6 meters, you can see it on my antenna page.


The following are graphs of tested antennas and where they worked the best, keep in mind the one above worked great on 10, 15 and 20 and real good on 6.  
 

This one worked good on all three bands, with 20 and 15 working best.  10 foot spacing is a good compromise for 20 and 15 but drops off for 10.  
 

This one worked super on 20, great on 15 and good on 10.  It would beat the pants off any 4 element single band beam. 
 

This is probably one of the best compromises one could come up with for 5 elements on 20, 15 and 10.  With the closer spacing gives 15 meters the most gain here, 11DB or so, while the addition of a 5th element on 20 gets the gain back up to 10DB or so, and 10 meters is about the same.  This spacing also produces very good front to back on 20 and 15, but about 15 or 20 DB max on 10.  One must keep in mind with any antenna you reach a point of diminishing return, approximate gain with a 4 element Quad is about 10 DB.  One must double the elements to obtain another 3 DB.  The Big One theoretically produced 10 DB on 20 and close to 11.5 DB on 15, while 10 meter was around 12 DB.  Six meters was not far behind.

One more advantage of the quad that may not be known, metal elements or aluminum on beam antennas will produce rain static, where as the quad does not.  This may have been eliminated in the StepIR where the elements are inside fiberglass.  I remember running heads up single op single band in a contest against my friend Bruce AA8U one year on a rainy weekend, he had a quad and I had a beam.  Two or three times over the weekend the rain static on my end was 10 to 15 DB over 9 and I couldn't hear a thing, Bruce just kept right on going.  Needless to say he whooped me with well over 3 or 400 Qs.

Another thing one should know, you can broadband the quad by making the Reflector about 5.5% larger than the driven element and each director about 2.5% smaller as you go out.  This will reduce the front to back and slightly lower gain, but will allow you to have good SWR from CW through the top of the phone band on 20 and 15.  If you build for say a center frequency on 20 of 14.200 MHz for max gain and front to back you would use about 3% longer for the reflector and 2.5% shorter for the directors, all directors being the same size, not tapering down as you go out.  This will produce about a 1.5 to 1 SWR 50 to 75 KHz each side of center and climbing as you go further.  A two element quad is not as critical since only the reflector length starts to get into the picture as you go down.  If one wants good results for CW and phone with a two element, one could build the reflector for about 13.900 MHz and the driven for 14.150 MHz, you should be able to reach the top and bottom of the band with an SWR of under 2 to 1.

Good luck with your quad project and let me know how it works out.  In 1978 I received my Ph.D. (Positively Hears the Difference) Award by Clarence Moore (Inventor of the Cubical Quad 1942).

 

April 2009

I have been asked several times about how does one get a quad on top of a guyed tower.  First let me say I have been fortunate since 1972 to have a Heights self supporting aluminum type tower, it has been changed several times over the years when QTHs were changed, from 64, 80, 96 and now 112 foot.  With this situation even though I could never allow the tower to hold all the wind load in high winds, it was still guyed.  When taking quads to the top or lowering, the quad could be on a pulley and rope to the mast pipe.  Guys with no winds can be removed and allow one to pull the quad up to the top, when in place the guys reconnected and then one could go up and attach the boom to the mast.  Taking it down was just done in reverse.

As for a say Rohn 25G guyed tower removing guys is not an option.  I have helped put quads on top of these type towers and what follows is a good recommended way to do it without the use of a crane or helicopter.

Lets say you have a 100 foot tower and it's guyed at 30, 60 and 90 feet per Rohn's instructions, or any other arrangement in three directions, as long as you have the top 7 or 8 feet open above the top guys here's how it's done.

Across the flat side opposite any one guy set you can attach a 6 or 7 foot long boom piece, on the ends of the pipe is another set of guys running parallel to the set of guys on the tower so they are a few feet out past the tower guys ends at the ground.  That pipe you put on the tower should be a couple of feet above the top guys.

At the top of the tower or preferable on the mast pipe you will mount a pulley so a rope at least the length two times longer than your top guy.  This rope is attached to the center of the quad which you lay across the two tram guys and can pull from the opposite side away from the tram.  The Quad is balanced across the two tram wires like a train track.  When the Quad gets to the top, the pulley being higher on the tower will pull it high enough so when the elements get near the other two guys it will go up high enough to not cause a problem.

As long as the quad is balanced, like a two, four or even six element quad it can be placed on top of your tower very easily.  Cost as compared to other methods is very reasonable, two extra guy lines, six to eight foot tram bar, pulley and rope.