I got interested in making a DIY 2 meter handheld antenna for Fox & Hound use. Here are the pics and info about this project.
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>Any questions or other related queries, contact me at W9LRG <at> arrl.com, I will gladly answer to the best of my abilites and listen to yourfeedback on my website.
At a meeting of MCWA, Augst, 2024 there was a presentation of a 2m tape measure antenna by Ralph WB9ICF and a proposal to conduct
a 'Fox and Hound' chase in the near future. I love DIY projects. I started researching the antenna and found some interesting info.
First glance through the info I found I was missing alot of info on dimensions, spacing, etc. I then found YagiCAD
With YagiCAD, I had what I needed. Here is the YagiCAD file I used: TAPE1.YAG Open this file in YagiCAD.
It shows the length of the elements and their position on the PVC. In YagiCAD, click on Toolbox, then Match, then select Match Type 'Hairpin'.
Now click on Calculate. The hairpin should be 1.136 inches long and 1.575 inches wide. I found a piece of junk coax and used the center
conductor to make the hairpin.
I was given the 3D printer files for the mounts needed from Ralph WB9ICF. Ralph modified the boom mount from: Thingverse 2955797
Original pistol grip: Thingverse 5146800 These files assume using Sched 40 1/2inch PVC pipe for the main beam.
Here is a link to the 3D files from Ralph WB9ICF I used for this project 2m_3D_print.zip You need three of the boom_mount and
boom-mount-top. You will need one of the handle and handle-mount. The file VK3YMG plate is for a bigger plate to mout a discontinued
2m receiver.
I used the handle and handle-mount to mount the attenuator on the antenna. Despite it's size, the attenuator box is very light.
I got a friend to make the 3D parts for me. If you are a member of MCWA and need these, ask at a meeting or on the club reflector, you
will probably find someone willing to make them for you.
Besides a decent HT(BAOFENG's don't have a working S meter) with a working S meter, you need an attenuator. When you get close to the
Fox transmitter you will probably need to attenuate the signal to get a usable direction with this setup. I searched around and found an
HMC472 RF attenuator on Amazon for about $10.00. It's a 5volt chip mounted on a board with DIP pins for the +5v input and for selecting the
different db attenuation values. I mounted mine in a box with 7 SPST switches(pics below). I mounted an LED to show if it's turned on,
a 9v battery, a 7805 voltage regulator to feed the board. One switch as on/off and the other 6 to select the different attenuation values.
This board can insert 0.5, 1, 2, 4, 8, or 16 db of attenuation. If you select all, you get 31.5 db of attenuation.
If you use a project box with a clear top, the HMC472 board has an LED on it to show it's powered on.
When your HT is connected to the antenna through the attenuator, DO NOT TRANSMIT! You will release the magic smoke inside the
HMC472 chip and you get to buy another one! You have been warned
Here's a picture of the completed antenna, attenuator, and HT connected. The elements(front to back, director, active, reflector) are
one piece for the first(director) and third(reflector). The active element is two pieces. Solder the coax center to one piece and the braid/shield
to the other and the hairpin to both of these elements. From a DC standpoint, you should see a short using a standard VOM.
When this project was completed, I used the HT's builtin NOAA weather channels to test the the antenna and attenuator. It was a success!
BTW, I went overboard and used plasti-dip on the tape measure ends. I always wanted an excuse to use plasti-dip and this was the perfect project to play
with it! I also made the main beam longer that I saw in other photos. I use that extra length to tuck the end in my arm pit to help hold the antenna.
This is a picture of the HMC472 RF attenuator. I was able to source this at Amazon.
This is the spec sheet for the HMC472.
This is a close up of the faceplate for the case holding the attenuator
Here is a close up of the inside of the faceplate showing the switches.
Here is a close up of the inside of the project box showing the mounted HMC472 and the attached cables..
Enjoy and please send feedback to my email address above, I like to hear from other hams!
Lyle W9LRG