Saturday, January 9, 2016

2 meter antenna


To celebrate my new licensed amateur status, I decided to build an antenna for my new radio.

The radio is dual band (2 meter/70cm), but I decided to start slowly and make an antenna for just the 144MHz (2 meter) band, since that's the one I'll be using most.  I found the specs here (part of a compendium) I used the rest of the compendium as well as other reference material, particularly this video by +Martin Lorton,

I enlisted the help of my brother-in-law, who has skills (see the generator house).  In the interest of using what we (he) had, we used a copper plate instead of aluminum, and 10-gauge wire instead of welding rods for the radials. There may be a galvanic action problem, but we'll see.

Materials:
4.       4-40 machine screws, washers, and lock nuts (4 ea)
5.       12 AWG wire (19 5/16” + loop,  4 x 20 3/16 +)
6.       Copper plate (~6” square)

7.       PVC pipe for stand

Process:
  1. drilled a 5/8" hole and four small holes (for the 1/2" 4-40 machine screws) in the copper plate
  2. attached the SO-239 to the plate with the machine screws
  3. cut the wires to length (4x#10, 1x#12, 19")
  4. bent the radials to 45 degrees, 4 inches from one end
  5. soldered (instead of screwed) the radials to the copper plate
  6. soldered the #12 wire to the center pin of the SO-239
  7. connected the cables to the antenna, each other, and the radio
  8. on the air (not yet...I need to hear activity in order to know what's up)
We found an old Archer 21-256 CB tuner (over 40 years old).  It claims to cover 2-175MHz. Just for drill, I cleaned it up and connected.  It showed my SWR was way off. I tried bending the radials up, and it got worse. I bent them down, not quite to vertical, and I got it to 1,2. I have no idea how accurate the device is or how effectively I used it, but I used it.

I have not raised anyone, with the antenna, but I had the same issue without it. This morning I heard 2 people on a local repeater and when they finished I asked if they could hear me. I had a nice conversation with one, so my radio transmits.  Now I just have to test the antenna.