The AA7BM 440/70cm Ground Plane "Tea Cup"
Well, it is starting to get warm and the Arizona sun must have fried what few brains I thought I had as I was thinking that no one makes miniature antennas unless they are doing portable QRP so I decided I wanted to make a 70cm ground plane, just to see if I could.
I do not do QRP or even much portable and my portable has a perfectly fine ducky that works very well thank you, so the only reason I have to make a tiny antenna is because I have some space to let in the upstairs attic.
Anyway, I call it a tea cup antenna as the cup I used is just a bit smaller than an oriental tea cup.
I started with approximately a 30 inches piece of #12
THNN, and stripped the insulation off it.
I purchased a package of four stainless steel condiment cups as shown in the photo above from Wally world and drilled a 5/8ths inch hole in one of them, turned it upside down, then I dropped the SO-239 down into that from the top.
I then cut four eight inch pieces from my wire, and rolled them between the counter top and a piece of wood to get them fairly straight. I then took a pair of needle nose and bent the tip of these four wires 90 degrees. Placing them between the cup and the SO-239 with the bent tips coming up through the mounting holes, I then soldered them in place. I had my radials. See photo below.
I drilled a hole in the mount for a self tapping screw to secure the mount to the cup (still have not done that as it works fine without it).
I then took the remainder of my wire, straightened it out like I did the radials, and soldered it to the center pin of the SO-239.
I connected a short jumper to the SO-239, (a bit tricky inside that cup with my fat fingers) and dropped the co-ax down thru a short piece of 3/4" PVC. I then put the antenna on top of the PVC and hooked it to my MFJ-269 and did the clip and bend technique until I got the SWR down as low as I could for the 440 repeater on Heliograph Peak 45 miles away.
I put an adaptor on the end of the coax to fit my HT and held it in my left hand. I then put the HT in my right hand, dialed in the 440.700 repeater and asked for a test. N7AM in Pima, AZ came right back and told me I was getting out. I thanked him and cleared, but immediately had another call from a man in Holbrook who said I was full quieting on his HT there.
This took me about an hour to make, and another 1/2 hour to tune for the 440-448 band. I had intended to make it a 5/8 wave, but didn't have enough wire so I ended up with only enough wire on the vertical to make what appears to be a 1/4 wave ground plane antenna.
The only real cost was for the SO-239.. everything else besides the stainless steel condiment cup came from the junk pile. The stainless steel condiment cup was only 79 cents at Wally world for a pack of 4.
Hmm, I still have 3 more condiment cups, can I do the same thing for 2 meters? What about 6 or 10?
B. McCabe, AA7BM
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