Eight Bay Bowtie Antenna Array

Introduction: Eight Bay Bowtie Antenna Array

In this Instructable, I will show how to build an eight bay antenna using "bowtie" elements. This antenna was designed to be resonant in the middle of the new, smaller UHF band, channels 14-36 or 470-605 MHz. The performance of this antenna is quite impressive with average dBd gain (gain over a dipole) of 12.79 or 14.94 dBi (gain over isotropic) averaged over 21 points. This is equivalent gain to a good Yagi. During tests indoors, I was able to get a couple of stations 120 miles away. Mounted outdoors, I'm sure it would get even more stations from that distance. If the antenna is to be mounted outdoors, I would completely weatherproof it with a couple of coats of rubber compound of the type used for insulating tools and put some paint on top of that.

Supplies:

1) Piece of old metal clothes hanger 21 x 52" (Can be substituted with chicken wire mesh of same size.)

2) Piece of wood 1 x 1 x 52" (Note: I used what I had on hand which was shorter than the frame)

2) Piece of wood 1 x 2 x 24

3) 20 foot piece of #14/3 AWG Lumex or Romex wire. If bare #14 copper wire can be obtained it would be better.

5) Plumber's strapping

6) Female 75 Ohm "F" Connector (can be purchased online or salvaged from old TV's or video equipment)

7) Electrical solder

8) Steel wool

Tools required

1) Various types of pliers

2) Various types of screwdrivers

3) Measuring rule with standard and metric markings

4) Soldering gun (150 watts minimum)

All except the 75 ohm F connector can be purchased at a home Improvement store.

Step 1: Cut Wire Sheath and Remove the Bare Ground Wire

Cut the house wire so that the bare ground wire is removed from the sheath. This bare wire will be used to make the bowties. This can all be done at once or you can just take it off as you need it. From this, cut off (16) 500 mm lengths. If you need more wire, strip the insulation off one of the colored wires.

Step 2: Attach Frame to Long Piece of Wood.

Attach frame to back of long piece of wood with plumber's strapping. Then attach 25 inch "foot" 15 inches above bottom of long piece at an angle with a 1 1/2 inch wood screw. Tighten screw to just allow some movement, this piece keeps the antenna and frame standing up straight.

Step 3: Start First Two Bowties and Attach to Wood Piece With Wood Screws

Make the first two bowties, take two 500 mm pieces of wire and bend in the middle. Make into open-ended triangles with the open ends 139 mm wide. The two 1/2 inch wood screws should be 11.5 mm apart and 69.5 mm below the top of the long piece of wood as shown in the diagram. The next two screws will be 150 mm below the top screws and the bowties will be mounted by tightening in the screws down. All eight bays should be mounted this way.

Step 4: Once All Bowties Are Completed, Start Installing the Phasing Harness

Once all the bowties are completed, the phasing harness can be started. cut two insulated wires, red and black or whatever colored wires you have and starting from the top, cross them soldering them in place to the bowties just to the right of the screws. Clean the wires with steel wool beforehand so that the solder will flow easily. Make sure both sides of bowtie are soldered together. Once the crossover has been completed, the next two phasing wires will go straight, connecting the second bay to the third bay. The third and forth bays are crossed over again. This goes on all the way to the bottom. The middle part is where the 75 ohm connector connects to the phasing harness.

Step 5: Once Phasing Harness Is Completed, the 75 Ohm "F" Connector Can Be Connected.

You might choose to directly connect a coaxial cable or an actual connector like I used. Either way solder the two wires to the phasing harness. The polarity isn't important. The connector box I used, I got out of an old TV. I temporarily hung it from a tie wrap. The plan was to glue it to the side of the wood with something like Gorilla Glue.

Step 6: Checking Out Dimensions and Making Sure None of the Bowties Are Touching

Once all the bowties are installed, the phasing connectors are all soldered in place and the output connector is installed in the middle, the bowties should be checked so that they are close but not touching. If they touch, the performance of the antenna will be compromised.

Step 7: Once the Antenna Is Checked Out the Performance Tests Can Begin.

I designed the antenna to have as good performance across the band as possible. The gain is relatively consistent up to 520 mHz where it takes a slight dip and then up to 580 mHz (channel 32) where it sharply drops off . If you want to have better response beyond channel 32, just take an inch or two off each bowtie. This would move the response higher in frequency giving more gain up to channel 36, 602 mHz.

In the first chart, I took comparison reading with a signal generator and field strength meter using a simple dipole, which has a theoretical gain of 2.5. The dipole is what other antennas are compared to when gain is being calculated. I took measurements of this antenna's gain at 21 points and then did the same thing to the bowtie antenna array. I then averaged the difference readings between the two and came up with an average reading of 12.79 dBd. This is gain over a dipole. comparable to the gain of a good multi-element Yagi.

The second diagram was made with a tracking generator, which is a sweep generator and a spectrum analyzer in one unit. Note how similar the two sweeps are. I was very happy with the performance of this antenna and when connected to a TV it picked up stations from 120 miles away!

STEM Contest

This is an entry in the
STEM Contest

Be the First to Share

    Recommendations

    • Clocks Speed Challenge

      Clocks Speed Challenge
    • Toys & Games Contest

      Toys & Games Contest
    • Big vs Small Challenge

      Big vs Small Challenge

    Comments