1/2 Wave 2 Meter Dipole Antenna
With two of my smaller fox transmitters as seen here requiring antennas with more gain, I went in to my shop and built the 1/2 wave 2 meter dipole antenna seen mounted on my analyzer.
The antenna proved to be a simple build, with a piece of protoboard (breadboard) used to mount the components on,
I initially cut 2 pieces of 1/16" (1.57mm) diameter music wire (found at hobby shops) measuring 20" in length, and then formed eyelets on one end of both with the use of a pair of needle-nose pliers.
I drilled a hole at either end of the tee shaped protoboard matching the machine screws I selected, and then I fastened the two dipole ends in place with the machine screws.
To allow the attachment of coax to the antenna, I used a female crimp SMA connector, and after attaching it to a 2" piece of RG-174/U coax, I striped back the coax and connected the braid to one side of the dipole, and then connected the center conductor to the other side of the dipole.
If your wondering how I attached the coax to the elements, I used tiny eyelets that are fastened in place with the fasteners holding the two elements in place on the protoboard.
I used double nuts, one set for holding the elements in place, the second set screwed over top to fasten the coax wiring in place.
When I initiaaly formed the T shaped piece of protoboard, I allowed for extra length to add a tye-wrap about 3/4" forward of the eyelets on the elements to keep the elements from moving out of alignment on the protoboard while being used in the field.
The very short length of coax used between the female SMA connector and the tag ends attached to the elements are also fastened in place to the protoboard with tiny tye-wraps.
Once everything was assembled, I attached the antenna to my analyzer to see what it looked like.
As I sais earlier, I initially cut the elements at 20" knowing that the antenna would need trimming to tune it for the segment of the 2 meter band that I wished to use the antenna for.
In this case that was the fox-hunting frequency of 146.565MHz, although the antenna is resonant in the rest of the 2 meter band also.
Hooked up to the analyzer, the antenna proved to be too long as I planned on, and needed to have the elements shortened to get it on the target frequency.
With my analyzer having a SWR graph available, it was easy to see what frequency the antenna was resonant on, and as I suspected, it needed to be shortened.
It only took a minute or so to trim the two ends of the dipole to make the antenna resonant on 146.565Mhz, and when it was all said and done, the elements measured 19" each after trimming, with the overall dipole measuring 39".
The last step required to complete the antenna, was to mix up some 5 minute epoxy, and with all the components mounted on the protoboard, they were coated with 5 minute epoxy and allowed to set up.
Once the epoxy had cured, I then cut 3 lengths of shrink tube, and shrunk these segments in place over either element, as well as over the coax with the SMA connector further securing the componets to the protoboard, and giving the antenna a more finished appearance
I also ground both element ends clean, and with my soldering torch and some solder, I formed tiny balls on the tips of the elements, and then shrunk short lengths of shrink tube over either end of the elements.
This gave the antenna a finished look, but more importantly, this is mandatory as not to poke yourself or someone else in the eyes with the very lethal ends of this dipole while handling the antenna.
This 2 meter 1/2 wave dipole has proven to be what I needed to dramatically improve the range of the two fox transmitters shown in the photo.
Of course it goes without saying that there are other reasons why you may want to use a 1/2 wave 2 meter dipole in the 2 meter band besides for a fox hunting transmitter, and with this antenna being simple to build as well as a good performer, capable of blowing your rubber duck antenna out of the competition, I recommend you try one.
One final note....although the antenna can be attached directly to the transmitter, in most cases I will use a seperate length of coax with SMA connectors, allowing the antenna to be mounted in either a horizontal or vertical position.
Click on the photo for a closer look.....
Using it in the field.....