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Home Brew Collinear

THE

W7LPN

VHF AIR DIELECTRIC

SLEEVED COLLINEAR
W7LPN Collinear PDF

DU1ANV
See bottom of his page for references to coax collinear

Fiberglass tubing Aluminum tubing Printable PDF
I am not an engineer. I don't claim to be an Antenna Guru. This is a fun hobby to me and as you might guess, I've learned a lot from my early assumptions. The following projects have been very fun for me and I wish to share them for that reason alone. They have been good performers and were well within the abilities of most "Shade Tree Mechanics" or "Home Brew Enthusiasts". I am not trying to lessen the importance of the projects of any other ham. Enjoy & share & e-mail me with comments at mycallsign.hamradio@gmail(dot)com. In the drawing text, the antenna elements are 19 1/8th and 38 1/4" respectively. Over time I have changed this to the true wavelength of 19 1/4 & 38 1/2". Air Dielectric measurements are closer to true than coax velocity factors, and using the tip for tuning eliminates any need to change dimensions. The next upgrade will include 5/8 wl elements as the center portion of this collinear design. It will still have the 1/4 wl at the base and top as this appears to keep the phase shift correct. NOTE: For PVC dual wall models, always use heavy wall PVC for all parts. The thin wall will be far too flimsy.

Note: Some experimenters have reported high swr and poor analyzer readings even while this antenna out performed their commercial antenna.
A field strength meter will show true readings from the finished antenna.

Home - Frazier Antenna's

This design was built with PVC & Aluminum foil as a ultra inexpensive test bed. It performed very well. My design is not allowed on the ARRL web page in my opinion because it it competing with advertising dollars for QST magazine. One of my fellow hams modeled this design and built his own, but was not allowed to post it on ARRL.

Joel Hallas W1ZR wrote

"...I believe that what you have is an adaptation of the collinear that was in early ARRL Antenna Books (for example 13th edition, p 248). That antenna used sections of alternating RG-8 coax as the elements. If this is the architecture you followed, I believe your approach may be an improvement since the relative velocity of your mostly air dielectric "coax" will be close to 1.0 and thus the element lengths work out better from an antenna perspective.... The way coaxial cable works is that if the current on the outside of the inner conductor are equal and opposite to the current on the inside of the outer conductor, they cancel outside the outer conductor. Note that due to skin effect the current on the outside of the outer conductor (the antenna current) is a different matter and has nothing to cancel it. This, the cancellation effect, has nothing to do with diameters, except that the outer must be larger than the inner, so the inner can fit inside....By not being centered, the characteristic impedance will vary somewhat, but that is not a big deal, IMO. The thinner wire will be okay, however, the loss will be somewhat higher due to the additional resistance. Also not a big deal."

GL & 73, Joel

Joel R. Hallas, W1ZR

Technical Editor, QST

end quote

COPPER FOIL OVER PVC

WATER TIGHT FERRITE BALUN

UP AND WORKING
The next one I build will have 1" PVC inside 1.5" PVC and I will check it's durability in wind & weather. YD2WPE Eko used this configuration in Java atop a 40ft tower with good results.

New Model
The W7LPN Collinear 2m/440

The above drawings depict a antenna design constructable with a wide variety of materials, from PVC and copper tubing, galvanized conduit, aluminum tubing, even foil or mesh hardware cloth. It is a very forgiving design as to construction materials and slight dimensional variations. For this design I have used PVC and aluminum. The drawing depicts 5 separate sections of PVC. This is not necessary. Two 10 ft X 1" lengths will work for the inner section. The diameter of the outer radome will have to be decided after the inner is finished depending upon materials and construction techniques. It is a simple vertical sleeved dipole with #1 and #5 elements each being ¼ wl and the three additional ½ wl adding gain and becoming the collinear. However you figure gain, dB or dBi, it is 4x a full size dipole. The thin wire runs through the center and of course the tubing is outside. This configuration allows the natural phase shift to occur at ½ wavelengths by alternating element sizes instead of wasting RF energy in the form of heat by using capacitors at each element or loading coils. Since the thin wires do not radiate, they may run inside and skip the element fed by the other side of the vertical dipole. Hence, the center conductor of the coax starts @ element #2, the shield @ element #1. Each side skips one element and is attached to the next, alternating contact with each energy source. It may be advisable to cut element #5 a bit long as it serves as a tuning stub if necessary. I have not had tuning trouble, but during his first build of this model, Eko Pramono YD2WPE Java Indonesia extended his #5 element to obtain suitable swr. Before the extension, he was centered at 150MHz. After trimming he states, "Right in the middle of the band". Some good reading: http://home.comcast.net/~ross_anderson/sc.htm

The large diameter models may be broader banded but will be more gangly and in need of support. I used fiberglass outer radomes and this proved to be very strong. A single support at the base was sufficient. Eko Pramono used two layers of PVC bonded with the elements in between. This added rigidity and proved successful on his 45' tower in Yogyakarta, Java, and said “Its performance compares closely to the Hustler G-7”. After placement of the elements and thin wire, the most critical part of the design is the balun. I used 7 X #43 ferrite beads, sealed and fixed securely in place @ 38 1/2” from the tip of the lower element as seen in the first drawing. If the balun slips, it will de-tune the antenna. An Ugly Balun may be a better choice for you. Lastly, if you are on a tight budget and want to experiment, get some scrape tubing, or thin sheet metals/foils, some PVC and go for it. I have used galvanized tin, wire mesh, copper, aluminum & foils, without notable change. The least expensive and best performing model so far is made with 2 layers of PVC, heavy butcher grade aluminum foil, and two continuous strands of aluminum electric fence wire on opposite sides explained in detail below. A hairpin match was suggested, instead of a ferrite balun, by a colleague, but without the ferrite beads, sleeved verticals tend to send stray RF down the shielding, so the ferrite balun serves a combined purpose. I have not noted problems with bead saturation & de-tuning. Try it on other bands. Make one for your volunteer fire department, etc.. I hope you have fun with this antenna, and come up with a combination that works for you, in the most economical way.

Caution-- Read this first before beginning assembly.

Aluminum Foil-- One of the better performers and definitely the least expensive versions so far. Total expense, minus supplies already in hand was <$25.00. I used heavy duty butcher grade aluminum foil and bare aluminum electric fence wire. I used #40 pvc 1" x 10' x2 pieces with 1.5" x10' x2 pieces. The 1.5" completed tubing is capped and laid aside. The 1" pieces are joined as described below. the feed point and spaces between the elements are taped off with masking tape. Starting at either end, tape off the spaces between elements, lightly spray adhesive where you intend to afix the aluminum foil. Measure and cut aluminum foil in existing width and the lengths of the elements in the drawing. Pull the wrinkles out of the foil and align it vertically so it can be wrapped around the pvc. when 3/4 wrapped around, lightly spray adhesive on the dangling foil. Then finish wrapping around. Cont to each subsequent element. When finished, drill access holes in opposite sides of the PVC to run each leg of wire vertically. I drilled a 3/8" hole near the #1 element, fed the split and finished coax ends from the base of the 1" pvc up to the feed point, pull out the shielding, and secure it to the outside temporarily. Drill a second hole on the opposite side near element #2 and pull out the center conductor and secure it. Remember you are going to run in & out skipping contact with every other element and laying the exposed wire atop the foil. Drill the hole near the element you intend to feed (have contact with the foil). Pre-measure and cut the electric fence wire two full antenna lengths. insert the first at the shield feed point hole, push it in to skip #2 element and exit near #3 on the shield side of the pvc (hemostats work great for pulling the wire out). Just past #3 element drill another hole and insert the tip there, push it through #4 to exit near #5 to terminate in contact with it. Anchor the shielding and aluminum wire with a self tapping screw, gently, to the foil. Work the slack toward the tip and start the screw. If you pull the wire around the screw you can keep it taught while securing the screw. It's a good idea to use battery grease, ox-guard etc. on all contacts to prevent oxidation especially where copper meets aluminum at the feed point. Repeat this method on the opposite side, feeding the center conductor to the elements by-passed on the previous side. Wrap the finished elements with plastic box tape, the cheap stuff. I had my wife turn the tubing while I kept the roll tight and spun my way to the tip. Insert the finished elements into the finished outer radome and secure with a screw near the tip and one at the base penetrating the inner pvc enough to secure it's placement. I used snap on ferrite beads because i had some on hand, 7 each at the base, 38 1/2" from the lower tip of element #1. It stormed last night with wind and rain and it survived just fine. I will not secure the inner pvc permanently in case of need for repair or adjustment, as this was a new method. Once proven it will be filled with injectable foam insulation between the elements and radome. I mounted the base extension to my mast with 3 hose clamps. If a short stub of PVC is lined up in the groove between the mast and antenna, it prevents the antenna from turning, twisting, and leaning to one side as seen in the photos. So? Do you want to have fun building an easy high gain antenna you built yourself, for a few bucks, or buy an antenna made in a sweat shop in China, pay $200 and the Manufacturer only got $30, and the kid got $1.00? Not Me!!

RIGID TUBING AND COPPER WIRE
Things I've learned along the way... Start with 2 X 10ft X 1" sections of heavy wall pvc. There is no pvc coupler joint, which fits inside the PVC allowing for a smooth exterior without changing the diameter. I cut a 4" section of 1" pvc and split it with a hacksaw to make it able to be squeezed to a smaller diameter and used as an internal joint coupler. It will hold enough to assemble the antenna. You must thread the thin wire the full length of the tubing while joining these sections. It is very difficult to do afterward. Leave a couple feet hanging out each end and secure to the end of the pvc so you don't pull it all the way in. I also use a length of coax with enough extra for a coax balun if I choose to use one, and no PL-259 yet, so it can be place near the end of the pipe when finished. Split the coax and braid, and gently tin the braid all the way around the coax and to the tip. This will give you something secure to grab at the feed point holes. The Feed-point- Drill holes in opposite sides of the pvc big enough to reach in with a hemostat(medical clamp) or small long tip needle nose pliers. Pull the center wire out one side to attach to #2 element, and pull the shield out to attach to #1 on the other side. Then alternate with thin wire elements and large tubing. When you have assembled the desired # of elements trim the excess pvc from the tip leaving a couple inches to secure with a screw to the outer radome. Yes, you can add to, or subtract elements to make it higher or lower gain....much longer will require guy wires.

Life is an educational journey. I don't know it all, but I know how to build these. If any of this doesn't make sense, please e-mail me with questions & I will be glad to clarify or guide you through the build.

The previous designs bellow

Tri-Band Sleeved Collinear Home-Brew 2m/440/6meter Supplies & Suppliers: Fiberglass Tubing from Max-Gain- 4 sections 1 3/4”x48” & 2 sections 2” x 48” Fiberglass Tubing Galvanized Hardware cloth 1/4” or smaller mesh at any Hardware store- 3 sections 38.25” x 4”, 2 sections 19.13” x 4” #18 insulate wire 20 feet. Wooden Dowels- 2 pieces 1 1/4” x 6” Drill with 8” x 1/2” bit & press. Drill 5 pieces with 8” x 1/4” drill bit and drill press. Drill pressed center end to end as best possible. Near the center on opposite sides, drill 45 degree angle holes down to the center whole. Both holes should exit the dowel near the center 180 degrees apart, on opposite sides. This helps pull the wire through. 5 ft RG-213 with high quality PL-259 at one end. Strip about 3 inches of insulation back and twist the shielding together so both conductors may be pulled through the dowel later. Leave about ¼ inch inner insulation on the center conductor to isolate them electrically. 7 pieces of #43 Ferrite Beads, must slide them over coax now before assembly unless you leave the PL-259 off until later. Marine epoxy- Boating supply stores Hot glue gun. The basic construction of the Tri-Band Collinear consists of an outer radome of 1 3/4” and 2” fiberglass tubing with a PVC cap at the top. I purchased the tubing from Max-Gain, and had them cut to 48” for shipping. The exact length of sections or placement of the joints is not critical, as long as you end up with enough total length to house the entire assembled internal parts, about 18 feet. To assemble, join the 1 3/4”x48” sections with marine epoxy and 2”X 12” sleeve tubing epoxied over the joints to reinforce and strengthen it. Total finished length is about 18 feet. Secondly, the guts of the antenna consist of 1/4” hardware cloth sections cut 38”x 4” and curled around 1”x 6” wooden dowels placed between each element. If you have a long enough working area lay out all the mesh on the floor end to end starting with a 19” section and ending with a 19” section. Place the finished dowels between each element and at both ends. First staple the mesh on the ends to each dowel making one continuous piece, leaving an electrical separation between elements of about 1/2”. Curl them around the dowels at the ends of the 38” lengths by wrapping the 4” around the dowels to form a 1 1/4” mesh and wooden tube. The center edges of mesh between the dowels will be opened a little. Don't worry about that, but make sure the sharp edges are bent inward slightly. Staying open helps keep it flexible while inserting it into the tubing later. The dowels have been center drilled end to end to run the thin wire through. It doesn't have to be perfect. This allows you to maintain the thin wire #18 centered. Think of the thin wire as the center conductor of a piece of coax and the mess as the shielding. The thin wire is threaded through the dowels and soldered alternately skipping one element at a time and soldered 180 degrees from the other thin wire connection to separate the connections electrically. Element #1 drops down over the open end of the coax as a decoupling sleeve with dowel #1 drilled 1/2” slides over the coax. Solder the shielding to the upper end of element #1 on the opposite side where you will solder the center conductor to element#2. At that same spot a thin wire is soldered to the shield and threaded through dowel #2, between elements 1 & 2, up through dowel #2 to element #3, which is repeated to #5. 45 degree holes were there to pull the shielding through and downward, and the center conductor up and outward. Element #2 is soldered directly to the center connector, then a thin wire from the top of element #2 threaded though dowel #2 up and through dowel #3 and soldered to element #4. Thus, #1 shielding decoupling element conducts to #3, which conducts to #5. #2 center lead conducts to #4. The finished internal parts are very close to 13 feet in length minus the balun. I chose to use the other 48”x 2” fiberglass tubing as a bottom mounting stub and to cover the balun for weather proofing. I slid the 2” tubing up over the 1 ¾” tubing, 2 feet to reinforce the base and leave enough to cover the balun. The Balun is provided by placing 7 pieces of #43 ferrite beads at 38” below #1 element. Everything is sealed air-tight within the fiberglass radome. If you are familiar with the “Coax Collinear” made from RG-58 of similar length elements, all I have done here is use larger elements for broader band width and removed the velocity factor shortening of the coax, borrowed the thin wire alternating with large diameter elements from the Simple Collinear, and beefed up the wind loading. Practical reception should be better due to the increased overall length. This is a very strong antenna.

Note: these early test were made to prove to myself and others that the design is sound and the materials used is not critical.

The above antenna was dismantled in the mistaken belief that a wire had burned due to excessive RF power, based on higher SWR in the lower half of the 2m band. Later after dismantling it I found the balun ferrite cores had slipped down the coax about 8". The elements were dammaged while dismantling and will be rebuilt using galvanized roof flasching curled around a solid 1 3/8"X 12' Maple closet clothes rod, and 18ga thin wire vs 22 ga used before. This is accomplished similar to the above, but using a propane torch to gently heat and curl the metal, while tapping it into the tubing, by tapping on the end of the clothes rod with a hammer. This process is proceeding quite well to the half way point. This design apears to be very forgiving regarding ther materials used. As long as your measurements are close, cutting or lengthening the top element will fine tune VSWR.

ALL VERTICAL COLLINEARS MAY BE ADJUSTED FOR SWR BY ADJUSTING THE LENGTH OF THE TOP ELEMENT LIKE A TUNING STUB. THIS HAS WORKED VERY WELL IN TESTING. Feel free to join this wiki and add your own projects

W7LPN 2m/440 vertical dipole The project below is my own design for a dualband vertical dipole for 2 meters and 440. It requires a balun and works very well. I like to tinker, so when I finish one project, I go on to another, even if it works well. There are several methods of constructing a vertical dualband dipole and a simple method is shown first below. Note that you do not have to follow either of the methods below exactly. You may choose your own method of construction and mounting, materials, etc. W7LPN VERTICAL DIPOLE (The simple method....coax exposed)

THE LENGTH OF THE HAIRPIN MATCH MAY NEED TO BE ADJUSTED SLIGHTLY FOR BEST VSWR

W7LPN VERTICAL DIPOLE Supplies: Copper tubing 1/2” X 48” precut piece w/2 end caps PVC-Yellow striped same O.D. As copper Boom= PVC “T”s and ¼ wavelength tubing One “T” must be 1 ¼ “ with 2 hose clamps to mount to Mast NOTE: The "T" on the Mast end and the boom must match with the same inside diameter (I.D.) as well as matching the "T" holding the copper elements. The boom or cross arm must go inside each "T". Plumbing store clerks are often intrigued about what you're building and don't mind helping you match parts. HOW TO BUILD A DUAL BAND VERTICAL DIPOLE? The simple method in the picture above is accomplished by surface mounting the coax to the PVC which should be one of the more simple methods and the picture should be simple enough for most to understand without major instructions. Some of the construction methods within this article pertain to both the simple version and the more complicated method. The more complicated method?: Another, but more difficult method, is to run the coax inside the PVC cross arm starting at the point where the antenna is mounted to the support mast. Using this method still leaves us with the mounting and support of the balun near the feed point situation. The simple method suggested first above may be the best for most builders of the vertical dipole for 2 and 440. Use your imagination and experience with various building techniques and experiment! These instructions below are for the more difficult method but will hide the coax at the cross arm and will cover and seal the feed point connections. With whatever method of construction you choise, it is suggested that all feedpoint connections be sealed from the weather. Starting with the 1/4 wave cross arm PVC, drill holes to accept coax near each end leaving enough room on one end for 5 or 6 wraps of the balun near the center insulator T, then drill one more hole in the cross arm (boom) near the end of the balun NEXT TO the final location of the center T insulator for the coax to be fed into the center insulator.

UGLY BALUN

During the procedure above, pull enough coax out to form the balun while leaving enough to work with to make the feed connections and wrap the balun around the PVC near the end of the cross arm and back inside the PVC cross arm then secure both ends of the wrapped balun with zip ties or hot glue to the cross arm so the balun will not spread apart or move in the wind. Cut & cap copper, 20” for each half of dipole. This length works well on both bands. Split 1 1/4” PVC -T lenghtwise to slide over support mast. (See mounting to mast below) Trim coax end & solder connectors on each conductor of coax Slide copper element ends into center insulator T and screw coax leads to copper antenna elements. Secure with solder and then make certain ends of elements are not touching and position the elements inside center T of vertical. When sure of connection and position of elements inside T, fill T ¾ full with hot glue. I feel very strongly about the "T" center insulator piece being sealed inside with hot glue, out of the weather and secured where the leads cannot get yanked out or wet and corroded. I hate water inside and it's effects on antenna joints and connectors. The time should be taken to do this on either design. Don't get hot glue on surfaces of PVC to be glued Epoxy T's in place ensuring vertical orientation. Hose clamp to Mast at top and bottom using split T and hose clamps. Again, see mounting to mast section below for details. YES! I believe in keeping it easy, but I found placing the coax inside the PVC to be surprisingly simple, clean and professional looking, water-tight, and smooth externally, as to not catch on anything. I am fairly good with my hands but for those of you with large hands or fingers, you may find it difficult to build the version with the coax inside the PVC. Securing the balun - I like hot glue. It's cheap, water proof, and the stuff stays where you put it. If you glue it before you're sure, it's a mess and won't come off. If you might have to tune or adjust something, don't use hot glue until it's tested and you're sure of the final position, length, etc. You can use the zip ties, string or other methods to hold the balun in place during testing. Put a little hot glue in the drill holes as well. I like the clean looks of none or little coax showing externally. MOUNTING TO MAST The split "T" which mounts to the Mast is cut lengthwise, making two cuts 1/4" apart to remove some PVC material in order to be able to "squeeze" it with the hose clamps wrapped around the "T" and mast. Without material removed in the cutting process above, the edges hit and it wont make a tight enough contact with the 1 1/4" T.V. mast. Obviously I left the coax connectors off until the antenna was finished.

BUILD A WOODEN FORMING JIG & FILL THE COPPER TUBING WITH SAND TO PREVENT COLLAPSING GENTLE HEAT MAY BE APPLIED. DON'T GLAZE THE SAND WITH EXCESS HEAT OR YOU MAY NOT BE ABLE TO REMOVE IT. IF ONE DRILLS A SMALL CONDENSATION DRIP HOLE IN THE BOTTOM LOOP, IT WILL NOT FREEZE FULL OF WATER IN WINTER AND BREAK D/T EXCESS WEIGHT.FOLDED DIPOLES ARE VERY BROAD BANDED. IT HAY BE NECESSARY TO ADJUST THE LENGTH OF THE TUNING COAX, BUT THIS SHOULD BE VERY CLOSE. AFTER MANUFACTURING 2 OR 4 OF THESE THEY MAY BE MOUNTED 1/4 WL SPACING FROM TIP TO TIP, AND VERTICALLY ALIGNED. A TUNED HARNESS CAN BE MADE BY BY USING 1/2 WL OF 70 OHM COAX FOR THE FIRST 1/2 WL TO A "T" CONNECTOR, THEN CHANGE TO 50 OHM. IF A DOWN TILT IS DESIRED DIFFERENT DEGREES CAN BE OBTAINED BY UP TO A 30% DIFFERENCE IN THE 38" LENGTH OF THE HARNESS WITH THE SHORTENED COAX FEEDING THE LOWER ANTENNA. THIS ALLOWS THE LOBE TO FORM FIRST IN A DOWNWARD TILT, THEN IS "PUSHED" ALONG BY THE UPPER ANTENNA SO THE LOBE REMAINS SKEWED DOWNWARD. A TEN % DOWN-TILT MAY BE PLENTY FOR NORMAL OPERATIONS, UNLESS MOUNTED VERY HIGH OR FOR REPEATER USE.

Phasing Harness

FOR QUESTIONS COMMENTS OR SUGGESTIONS E-MAIL RICK@

w7lpn.hamradio(at)gmail(dot)com

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w7lpn	Latest page update: made by w7lpn , Mar 24 2012, 11:18 PM EDT (about this update About This Update Edited by w7lpn 1 word added 60 words deleted view changes - complete history)
	Keyword tags: 2 meter antennas Antennas ARRL Base antenna Boise Ham Radio Coax Collinear Collinear Home Brew Antennas mobile auto tuners Mobile Ham Radio Moble auto-couplers VHF/UHF antennas Voice of Idaho Ham Club W7LPN More Info: links to this page

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Anonymous

Element spacing?

Mar 5 2012, 3:09 PM EST by w7lpn

Thread started: Feb 26 2012, 7:21 PM EST Watch

Do you have info on element spacing vs. tuning, did you just get at as small (tight) as possible?

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w7lpn

Building Questions?

Apr 17 2011, 10:20 PM EDT by w7lpn

Thread started: Nov 12 2009, 11:52 AM EST Watch

I have been getting a few e-mails with questions and building challenges. Feel Free to post questions here.

1 out of 1 found this valuable. Do you?

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Anonymous

aluminium or copper wire?

Apr 17 2011, 10:17 PM EDT by Anonymous

Thread started: Mar 7 2011, 7:02 AM EST Watch

Hi,
why did you use aluminium wire? if you used copper what guage would you have used instead?

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