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[Articles Home]  [Add Article]  

Durable Easy To Build 4 Element 6 Meter Quad

from Steve, WA8UEG on August 4, 2013
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Durable Easy To Build 4 Element 6 Meter Quad
Or 6N2 Or 4 Element 6 And 5 Element 2
Permanent Or Portable
You Decide Based On Your Needs
By Steve, WA8UEG

With 6 meters getting it’s magical properties back I started thinking of all the fun I had back in the late 60’s and early 70’s operating six meters and the bug to get back on the “magic band” bit me. Soon I was in possession of a IC-505 and 200 watt 6 meter amp. I quickly put up a dipole at 50’ or so and made several contacts during openings but before long it became apparent that a better antenna was needed. Living at a high altitude has its advantages especially when it comes to VHF and with an antenna with good gain at about 2000’ ASL my thoughts went to building a quad and getting serious.

My needs were only for 6 meters so I built mine as a mono bander however adding 2 is simple but there are a couple of options to decide on if you want 2 meters also. The element spacing for 4 elements on 2 meters is much too wide. My best guess is that using the existing spreaders as is will result in a DB or so reduction in expected forward gain and a lousy front to back ratio. If your currently using a rubber duck, ¼ wave mag mount on top of the filing cabinet or a ground plane and just want to be able to better access repeaters or reach out to some that are further away then your current antenna allows then using the 4 existing elements should work fine and be a huge improvement, just feed it on the horizontal arm rather then the vertical arm for vertical polarization. I don’t think the match will be too good so you will probably need a simple matching system which will be detailed at the end of this article. If on the other hand your interested in weak signal 2 meter work I suggest you add 2 elements, a properly spaced reflector and first director making it 5 elements on 2 meters and feeding it for horizontal polarization as described during the construction for 6 meters.

Material Needed:

(1) 10’ 2 3/4 in schedule 40 PVC pipe cut to 8’ and 2 end caps.

(16) 4’ electric fence Sun Guard II fiberglass Step in stakes (20 if you will be adding 2 Meter elements) I purchased mine at Tractor Supply for $1.95 each. These are perfect for spreaders.

(1) SO239 and screws for mounting (2 if doing 2 meters)

(1) Crimp on electrical connector (2 if doing 2 meters)
(<100’) #16 or #14 wire. I used #14 stranded copper but just about anything will work. More per the 2 meter dimensions if including 2 meters.

(1) Can of spray paint for plastic if you want the boom to look pretty.

All dimensions and spacing are listed at the end of the article.

The first step is the only difficult part of building this antenna. First cut the boom down to 8’ you can leave it at 8’ or cut it down to two four foot sections so it’s easier to work with and portable. Now you will need to mark the holes on the boom where the spreaders will be mounted for a reference point. There will need to be 2 holes clear drilled through the boom and 2 more at a 90 degree angle spaced ½ inch in front of the first two to allow the rods to clear each other when inserted, this needs to be done for each set of spreaders. It is important that all the holes are at 90 degrees and in line with each other. If you are adding the 2 meter elements you will need to drill one hole on the horizontal plane and one spaced ½ inch away on the 90 degree plane spaced from the driven element per the 2 meter reflector and director dimensions at the end of the article. (you will only need one rod in each plane for the additional 2 meter spreaders).


Boom marked for drilling

To properly drill the holes a drill press is a must, the size of the holes need to be 3/8” (the spreader arms are 3/8” so the fit is tight and to push in or adjust requires grabbing one of the wire holders and twisting while pushing or pulling) Once I drilled the first hole I simply placed one of the spreaders through the hole and leveled it vertically with a carpenters level and then drilled the 2nd hole making sure the boom and spreader remained level. I then rotated the boom so the spreader was horizontal and re leveled both the spreader and boom after moving it up in the vice and drilled the 90 degree holes repeating this procedure for the remaining elements. You can make some practice holes on the 2’ piece you cut off if you need to practice.

Remember if your doing 5 elements for 2 meters to drill the additional holes for the 2 meter reflector and director per the chart.

A picture is worth a thousand words, below is what we are trying to accomplish. If you don’t have access to a drill press I would suggest taking it, marked up and ready to drill, to a small machine shop explaining what’s needed. It should only take them 15 minutes and you can probably talk them into doing it for free or maybe 10 bucks on their lunch hour.

Once you have the holes drilled your home free, the rest is a piece of cake.

Now it’s time to prepare the spreaders. Place one of the fence rods in a vice close to the step used to push the rod in the ground. Take a hammer and hit down on the step portion to break it loose from the shaft, a good knock will take care of it. Now twist the foot rest back and forth to loosen it even more with a pair of pliers. Next hitting the foot rest with the hammer drive the foot rest off the rod (I used WD 40 on the rod to make it easier) These are tight fits, if it seems to hang up use the pliers to twist back and forth and loosen again. If your doing 2 meters loosen, but do not remove, the bottom wire holder which will be used to hold the 2 meter elements using the same method. Do the same for the very top wire holder that will hold the 6 meter wire. The remaining 2 wire holders can stay as is as they are not used. Now prepare the rest of the spreaders in the same manner. If your adding the additional 2 meter elements you will need to cut each one down to 30 inches then remove all the wire holders left as well as the step from the 2 extras.

A good knock with the hammer then wiggle back and forth with pliers and drive off

Next were ready to make the feed line connectors, for these we will use one of the steps that were removed.

First remove the small rib running through the center of the rest with a utility knife so the SO239 will lie flat. See detail below.

Remove small rib shown on bottom left with a utility knife

Position the SO-239 in the corner of the foot rest so that the connector will lay completely flat on the surface and drill a hole to accept the SO-239 (make sure the flat portion of the connector does not ride up on the curved surface of the foot rest when measuring for the hole). You will notice that only 3 mounting holes will be useful the lower outside hole will not be fully on the plastic. Place the SO-239 in position and drill out the mounting holes including the one where only a little plastic is visible as it will be used as a strain relief for the element wire, If your off a bit and the connector will not lay flat use a file to open up the hole a bit before drilling the mounting holes also drill a small hole to allow strain relief for the size wire you are using in the smaller fin as shown in the third picture down. When mounting the SO-239 place a crimp connector over one of the lugs with the plastic cover removed from the connector, this will be used as a solider lug for the ground side of the driven element. Make another connector if including 2 meters. See completed assembly below.

First remove the small rib running through the center of the rest with a utility knife so the SO239 will lie flat. See detail below.

Coax connector installed

Next, remove one of the top wire holders from a spreader and replace with the feed line connector as shown below.

Feed line connector installed on spreader

If including 2 meters you will need to take the 2nd feed line assembly and replace the lowest wire holder (closet to the pointed end) with the feed line connector on either the same rod for horizontal polarization or another rod to be inserted on the horizontal plane for vertical polarization.

Next cut all the wires according to the chart at the end of this article, I cut them all and then color coded each element wire with weather proof tape of different colors. If using it as a portable antenna each element can be quickly identified without having to measure.

Below is the driven element ready to string coded blue

Now were on the home stretch, insert 4 of the spreader arms through the boom for the 2nd director element so that each one is protruding 5 inchesas measured from the boom to where the rod starts to taper to a point, this is not critical just an easy way to measure. See below.

Director 2 spreaders protruding out 5 inches

Now insert the driven element spreaders so they protrude 3 inches, followed by D1 protruding 4 inches and the reflector protruding 1 inch.

If including the extra two 2 meter elements insert each 30” rod through the holes so that equal lengths (aprox 14 inches) extend out on both sides of the boom and install one of the wire holders removed earlier about 2 inches down from the end of the 4 spreader arms (might want to coat with some WD 40). Turn the top wire holders on all spreaders so they are all in the same direction.

Place the end caps on the boom and if your going to paint the boom, now is the time. I painted it the same color as the spreaders arms (sort of). NOTE: PVC & sun do not do well, so paint is advised.

Grab the 6 meter reflector wire and bend it around the top outer most spreader arm wire holder so it will hold in place then run the wire through each upper wire holder on the remaining 3 spreader arms, when your back to the first wire bend it around the holder as the 2 ends will be twisted together and soldered later.

Next do the same for the driven element so that each end of the wire terminates at the feed line connector. Run the end for the center conductor through the strain relief in the plastic fin and the wire for the ground lug through the SO-239 hole.

String the remaining wires for D1 & D2 in the same fashion as the reflector.

Now wrap the 2 wires at each element together and solider. Bend and trim the wire at the SO-239 so its neat and solider one end to the lug and the other to the center connector of the SO-239.

Wires spliced and soldered

Set the quad on level ground and adjust each spreader arm so the the wires are taught but do not bend the spreader arms. Do this by adjusting each spreader an equal amount. I.E. if the reflector is too tight move each spreader arm in a half an inch rather then pushing one spreader arm in for the adjustment, moving each spreader on an element will keep everything square and in line. Adjust each element using this method.

Now wrap the 2 wires at each element together and solider. Bend and trim the wire at the SO-239 so its neat and solider one end to the lug and the other to the center connector of the SO-239.

Elements properly tensioned

If including 2 meters string the wires for the 2 meter elements now using the same method but adjust each one with the wire holders and do not readjust the spreader lengths. If using the extra 2 elements use the new reflector spreaders and do not use a 2 meter wire on the 6 meter reflector. If you added the 2 new elements it will be a 5 element quad consisting of one reflector (30” spreaders added), driven element, D1 (30 inch spreaders added), D2 & D3. Of course if your using it as is it will be a 4 element 2 meter quad using the existing spreaders.

If this is to be permanent seal the feed line connectors with liquid tape to water proof, use a small brush and PVC cement to lock all the spreaders in place then cut off the excess rods with a hack saw if desired, use a dab of epoxy where the wire lies in the wire holders to secure in place this will help prevent sagging under icing conditions.

If it will be used portable mark each spreader where it protrudes through the boom with a permanent marker or paint so you will not need to measure when re assembling also mark each spreader with a color code same as the element wire so it will go right back together. Once everything is in place adjusted and coded you should be able to take it apart in 15 minutes or so and re assemble in the same amount of time or less. To take apart push the spreader arms in, remove the element wire then pull out each spreader. The whole thing will fit in a 4’ bag such as a portable lawn chair bag.

If you’re doing portable a boom to mast clamp can be made out of painted wood and U Bolts, or you can make one out of some flat aluminum stock. I picked up an aluminum one I could make work at a hamfest for $1.50. There are also commercially available ones that are readily available on the web. If you a newbie and would like plans for one just drop me a line and I will be happy to send you “how to make” plans. It’s also possible to use a PVC T connector and short piece of PVC pipe as method of mounting to a rotor.

Initial testing registered a SWR of 1:3 to1 at the design frequency of 50.125 sitting on a metal ladder with the bottom elements only a foot from the ground. On a 12’ mast (shown at beginning of article) SWR was 1:2 to 1. The gain and F/B numbers were based on comparing to a 6 meter dipole and measuring from a portable receiver 100 yards away, another ham station 50 miles away and several beacons so not scientific but the best I could do. In a word the performance is outstanding.

Spreader Spacing 6 meter

Reflector to DE is 35 inches
DE to D1 is 30 inches
D1 to D2 is 28 inches

Wire lengths 6 meter

Reflector 21’ 1”
Driven Element 20’ 7”
Director 1 19’ 10”
Director 2 19’ 3”

Spreader Spacing 2 meter

Reflector to Existing DE is 15 in.
DE to New D1 is 12.285 in.
D2 use existing
D3 use existing

Wire lengths 2 meter

Reflector 29.824 in.
DE 29.102 in.
D1 28.232 in.
D2 27.384 in.
D3 26.564 in.

6 Meter Specs

Boom: 8 ft
Turning Radius: 6.5 ft
Gain: 12 db
F/B: 26db
Total Weight: 13 lbs

Member Comments:
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Durable Easy To Build 4 Element 6 Meter Quad  
by N6JSX on August 4, 2013 Mail this to a friend!
Interesting, but a little hard to follow....

Two things to reconsider in your design:
1. 2m gamma BNC connector will get water logged and make for very poor RF connections in WX. SO-239 is referenced in your article and a better choice.
2. Your 'gamma match' is simple but lossy. You might want to try using a bazooka/sleeve balun and tune the wire length for resonant frequency.
http://groups.yahoo.com/group/RDF-USA/files/N6JSX%20Stuff/ Bazooka-Balun.pdf
This is how I make VHF/UHF Quad/Quagi's for T hunting where we want as little loss as possible. More RF components in-line the more the signal gets attenuated.

And YES, to the arm-chair eHAM guru's --- 'Balun' is a misnomer as a Bazooka/Sleeve Balun is really an RF choke not transforming anything, but it works!

Your 2m wire dimensions do not seem proper, even for just one side of a quad element, typical for 146.000:
reflector.... 20.5" Zt = 82"
driver........ 20.0" Zt = 80"
driven 1.... 19.4 Zt = 77.6"
driven 2.... 18.3" Zt = 73.2"
(((1030,1005,975,920 / F) *0.97) *12)
 
RE: Durable Easy To Build 4 Element 6 Meter Quad  
by WA8UEG on August 4, 2013 Mail this to a friend!
Correct you are, I did not build the 2 meter portion and it sure looks like the wire length is more than just a little off. I would suggest anyone adding 2 meters re calculate the lengths as they should be closer to 21 inches not 29 inches! The spacing should work fine. Needless to say any connections should be water proofed.
Thanks for your comments.
 
RE: Durable Easy To Build 4 Element 6 Meter Quad  
by KC7YE on August 4, 2013 Mail this to a friend!
Too drill the boom, make a fixture: 2x4 x length of boom with Vee sawed entire length. clamp boom to 2x4 (C clamp ). Mark center line of boom, line up with drill bit on drill press table. Clamp a couple scrap blocks to table to index center line. Mark spacing, drill one set holes, rotate boom 90 deg, drill next set. Is very repeatable. Old machinist/pipefitter trick
 
RE: Durable Easy To Build 4 Element 6 Meter Quad  
by G4AON on August 5, 2013 Mail this to a friend!
I love quad antennas, I have a couple of home made ones for 6m portable work...

The gamma match on the 2m quad can be avoided by careful work in EzNEC, if the dimensions can be tweaked to obtain a feed impedance around 50 Ohms it just needs a choke balun on the feeder or if it's near 100 Ohms a quarter wave of 75 Ohm coax will match it.

See: http://www.astromag.co.uk/quad/ for my simple 6m wooden quads...

73 Dave
 
RE: Durable Easy To Build 4 Element 6 Meter Quad  
by WA8UEG on August 5, 2013 Mail this to a friend!
Dave,

Nice job on your quad. I am also a big fan of quads, my low band quad is a old Hy Gain Hy Quad I purchased in the late 70's and is still going strong today. Your correct in that no matching should be needed on 2 with some careful pruning, as I mentioned 2 should be an easy add but since I do not do any 2 meter work it was more of an after thought. What is unique with this design are the spreaders used. The ease of attaching the quad loops and the ability to easily adjust the loops along with the low cost and extreme durability and very light weight of the rods used. On 6 the SWR is good from 50.8 to 50.250. I use a simple tuner when operating AM or FM frequencies.
 
RE: Durable Easy To Build 4 Element 6 Meter Quad  
by JOHNZ on August 6, 2013 Mail this to a friend!
It is very refreshing to understand that the disability fraud cases who operate on 14313 and bicker with each other endlessly in 14313 threads on qrz.com are NOT representative of amateur radio today. Technical projects, such as this 6m quad, are a great way to improve one's growth in the technical aspects of the hobby. Last year, I constructed a 6m 4-elem quad, based on a design by KG4JJH. It performed flawlessly in every engineering test we put it through, giving better than 8 db gain under many operating conditions, including portable ops. The ten ft boom and 16.5 Lbs weight presented no problems. Soon as I can find time I would like to check this antenna out further too.
 
RE: Durable Easy To Build 4 Element 6 Meter Quad  
by WA8UEG on August 6, 2013 Mail this to a friend!
Thanks, couldn't agree more. Another article I wrote should be popping up here soon on re building CD45II and similar rotors.
 
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