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The Little Stick Antenna for 2 Meters
Article Courtsey LD Blake, VE3VDC, 4-07
An aluminium version of the Vertical Bazooka.

basic plan The "Little Stick" antenna is an aluminium version of the Vertical Bazooka design which was made from coax.

Both antennas come from the same sleeve dipole family as the Shakespeare Big Stick that gained enormous popularity amongst CBers and is still widely in use by Marine Radio operators. Hams have also produced many variations on the theme like the ones from KV5R and W7LPN .

There is much to recommend this design:

  • Very compact, only a meter tall on 2 meters.
  • No ground radials needed.
  • Fairly broad bandwidth.
  • Low radiation angle.
  • Between 3 and 5db of gain.
  • Low SWR, typically under 1.5 to 1.

But there are also a couple of problems:

  • Their feedpoints are difficult to construct.
  • Most are not adjustable.
  • They are difficult to mount.

There isn't a lot that can be done about the mounting problem. Because the bottom half of the antenna also radiates RF, you can't just clamp these antennas to a mast pipe. You need to make provisions to both insulate it from the support structure and stand it some distance away from metal objects.

The other two issues are why I wanted to try building an aluminium version of the sleeve dipole. I wanted to see if I could overcome some of the construction problems and produce a professional looking antenna that is adjustable. I believe I've achieved this by using a rather unique feedpoint construction technique.

The parts pile The parts you will need are shown on the left.

You'll need a piece of 1/2" tempered aluminium tubing, a piece of 3/16" tempered aluminium rod, two pieces of .4mm thick brass about 3mm X 40mm, a 3/4" hose joiner, (also called barbed inserts in the U.S.....search Google), an AS-1 whip adaptor, an SM-2 antenna bolt and, although not in the picture, a meter of RG-8X coax a PL-259 connector and an adaptor to fit the coax to the connector.

The AS-1 and SM-2 antenna parts should be in stock in most ham shops along with the coax, connector and adaptor. The aluminium and brass bits can be obtained from most metal supply shops. The hose joiner is a common hardware item that can be obtained from most hardware stores or garden centers for a few pennies (buy 3 or 4, just in case).

There are two kinds of SM-2 connectors. You want the one with the larger (1/2") brass nut not the ones with the small (7/16") stainless one.

You should note there are two kinds of hose joiners, made from different plastics. The black ones won't work in this application because they appear to be conductive at VHF frequencies. Make certain you get the grey coloured ones.

Getting Everything Ready

End preparation The first step is to cut the aluminium bits to length.

The bottom section is made from the 1/2" tubing and is 397mm long. The length is determined by the velocity factor of the RG-8X coax. You can probably cut this most accurately with a tube cutter. Once you have your cut, take a rat tail file and make sure there are no sharp edges. Note in the photo on the right that I've tapered the ends of the tubing on about 45 degrees. This will become important when assembling the antenna.

You will want to cut the top section too long so that you'll have to trim it for lowest SWR. I cut the 3/16" rod to 570mm as a starting point knowing I would have to trim it several times to get the right length. This is a far better idea than starting off too short and having to cut a longer piece.

Next you want to get the two brass strips ready to make into your feedpoint contacts. Clean them up with a file, making sure there are no sharp edges anywhere then tin one side of one of them with a thin but even layer of solder. The solder helps prevent interaction between the brass and the aluminium that might lead to corrosion later on. This layer needs to be very thin because a thick or uneven layer might make the antenna impossible to assemble.

Formed contatcts The next step is to form the two brass strips as shown on the left.

The clip at the top of the picture is made from the tinned brass and will become the connection between the coax shield and the lower section of the antenna. The long side is 25mm. The short side is 6mm long. When you bend it, make sure the solder tinned side of the brass is on the inside of the bend and you should bend it a little more than 90 degrees.

The lower clip in the picture will become the connection for the coax center and the top of antenna. This is the untinned piece of brass. It will do double duty by providing the connection and also making sure the top section can't slide down and short out the antenna. Start with the shortest piece and bend it to 5mm on a 45 degree angle. The middle piece is also 5mm, bent to 90 degrees. The remainder of the piece needs to be at least 40mm long and will be cut to length later.

You should now check again and be sure there are no sharp edges on the brass clips. It might also be a good idea to check your bends with a magnifying glass to be sure there are no cracks in the metal. These clips will be under stress during assembly and you don't want them to break.

Prepared nut The next step is to disassemble the SM-2 antenna mount. You will want to take all the sharp edges off the nut as these may cause problems during assembly. The image on the right shows how I tapered the ends of the ridges.

And the last step is to take one of the insulating washers from the SM-2 and file off the shoulder that would normally keep it centred in a bracket's hole. You will need a flat plastic washer and this is a very easy way to get one.

Assembling The Antenna

Now that you have the bits and pieces all ready to go it's time to start assembling the antenna. The pictures below show how the parts fit together, as a side aligned view, without the coax in the way...

How it fits together Feedpoint closeup

Everything winds up inside the hose joiner. The antenna uses the pressure from the joiner to make connections by applied pressure between the clips and the antenna elements. Once the coax is attached to the clips forcing the hose joiner over the bottom tube traps the first clip and then forcing the nut into the top of the hose joiner, traps the other. This will form the feed point. Add the washer and the AS-1 adaptor and the antenna will have an adjustable top whip. And as a bonus, it can easily be made fully weather proof.

Coax ready to go The first step in final assembly is to prepare the coax with the brass clips. Some care is needed here as the spacing of the clips is quite important. You want the top clip to correctly position itself to sit a couple of millimeters below the bottom of the nut, when the top of the bottom tube is at the center of the hose joiner. If it's too long the clip may be damaged when inserting the nut, if it's too short the coax center lead may short to the lower element of the antenna. It should look like the image on the right.

Coax inserted Once you are satisfied the clips are positioned correctly, insert the coax into the lower tube so that the ground clip is on the outside as shown on the right. Be sure the tapered end of the tube is at the end where the ground clip is.

Now mark the aluminium tube where the bottom of the hose joiner will sit if the top of the tube is at the center of the joiner. This is your target depth when forcing the joiner over the tube.

The best way to assemble the bottom section is to get it started as far as you can by hand then gently warm the plastic with a blow drier. Don't get it too hot; it will melt. With only a little bit of heat the plastic will relax and let you go a bit more. Warm it again and then go some more. I put the joiner against a doorjam and put a wrench on the other end of the aluminium tube to press against, so I could get more leverage.

A couple of precautions are necessary. Be very careful not to cut the coax against the bottom of the tube. Also, the long side of the top clip is going to come out the top of the hose joiner as you press the lower tube into place, so be sure to allow it to move freely as you go.

The pictures below show the beginning and completion of this part of the assembly process.

Just starting The bottom is finished

In the right hand picture above you can see that I've already bent the top clip over. This is to prevent it from sliding back down into the hose joiner when forcing the nut into place.

At this point you should use an ohm or continuity meter and make sure the connections to your clips are still good and nothing is shorted. Measure from the aluminium tube to the shield of the coax at the far end and from the center clip to the coax center at the far end to confirm your connections. Finally measure from the top clip to the tube to make sure it's not shorted. If all is well, you're all set to insert the nut in the top section.

The nut installed The good news is that although still very tight, the nut will go in a lot easier than the bottom section did. First make sure the upper clip is laying flat against the inside of the hose joiner --not diagonally across it. Grip the plastic joiner, press the nut into place, get it started and push until the top of the nut is flush with the top of the plastic. When pressing this part into place don't use the bottom tube for leverage, you might accidentally move it, always grip the plastic hose joiner. You can use the same technique of warming the plastic a little as you used on the bottom section if you need to.

Ready for the Whip All that remains of the feedpoint assembly is to clip the brass tab off the side of the nut and assemble the whip adaptor on top.

To do this, put a little bead of silicon rubber on the edge of the joiner, place the plastic washer on top and screw in the AS-1 adaptor. Tighten the adaptor with a wrench, being careful not to crack the plastic washer and then add another bead of silicon around the base of the nut, where it mates to the washer.

After the rubber dries, insert the 3/16" aluminum whip into the AS-1 and snug up the setscrews.

Tadaa! All done Annnnd... on the left we see the finished antenna.

The last step is to install the coax connector on the other end of the coax. I suggest leaving a fair bit of extra coax on the bottom as you may have to make a choke with it.

I'm a bit fussy about coax length. One trick to use for single band antennas is to keep the coax a multiple of an electrical half wavelength long. I doubt this changes antenna performance much but, because a half wavelength feedline mirrors the impedance at the far end, it does mean that the readings you take at the back of the radio are the same as you would get from the antenna's feedpoint itself.

The general formula to make a half wavelength of coax is:

Length (in centimeters) == 15000 / Frequency X Velocity Factor

For RG-8X on two meters this is: 15000 / 146 X .76 == 78.1cm

Installation and Tuneup

I had a bit of trouble deciding how to mount and test this antenna. A couple of first tries were very discouraging as the antenna was too near the metal of my balcony. I finally found the best spot was directly above my balcony rail, on some PVC plumbing pipe, centered vertically between the railing and the bottom of the balcony above.

I had no problems getting the SWR down using the usual method of checking at both ends of the band, trimming and adjusting the whip, seeking an equal match on 144mhz and 148mhz and initially ended up with 1.2:1 at both ends with an absolutely flat match in the center (146mhz). In fact, this antenna adjusts very easily.

Once I found the right spot, the signal reports were encouraging. It did far better than my 1/4 wave monopole when talking across lake Ontario. Several repeaters were up an S unit or more and everyting seemed clearer. Plus there was a noticeable reduction in noise.

Easy mounting scheme I also took the antenna out onto the parking lot with my HT and did some tests there. It seemed quite happy to get away from all the metal on my balcony and I was able to open a couple of repeaters 50km away with the HT's medium power setting.

For those who want to build and experiment with this design, keep in mind that you have to keep it at least 30cms from nearby metalic objects; more space is better.

One of many possible mounting schemes is shown on the right, using 1/2 inch PVC plumbing parts. The T-fittings that hold the Little Stick are modified by filing away the internal ridges to make a slip through fit that goes over the Little Stick's lower section.

My sense is this is a perfectly good antenna design that will probably work quite well on top of a mast pipe, out in free space. It does work from the balcony, better than a 1/4 wave, but the large amounts of nearby metal do tend to reduce it's performance somewhat.

Editor's note: This project uses mostly metrics.
The "hose joiner" is also called a "barbed insert" in the U.S.
A substitute can be regular PVC pipe of the correct size.
Use this calculator for length and size conversion



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